diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 77c95fd55be3..200cef49f35d 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -41,7 +41,7 @@
 use fn_ctxt::FnCtxt;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, ErrorGuaranteed, pluralize, struct_span_code_err};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed, pluralize, struct_span_code_err};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{HirId, HirIdMap, Node};
@@ -204,7 +204,9 @@ fn typeck_with_inspect<'tcx>(
             );
         }
 
-        fcx.check_expr_coercible_to_type(body.value, expected_type, None);
+        fcx.check_expr_coercible_to_type_or_error(body.value, expected_type, None, |err, _| {
+            extend_err_with_const_context(err, tcx, node);
+        });
 
         fcx.write_ty(id, expected_type);
     };
@@ -274,6 +276,112 @@ fn typeck_with_inspect<'tcx>(
     typeck_results
 }
 
+fn extend_err_with_const_context(err: &mut Diag<'_>, tcx: TyCtxt<'_>, node: hir::Node<'_>) {
+    match node {
+        hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(ty, _), .. })
+        | hir::Node::TraitItem(hir::TraitItem {
+            kind: hir::TraitItemKind::Const(ty, _, _), ..
+        }) => {
+            // Point at the `Type` in `const NAME: Type = value;`.
+            err.span_label(ty.span, "expected because of the type of the associated constant");
+        }
+        hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(_, _, ty, _), .. }) => {
+            // Point at the `Type` in `const NAME: Type = value;`.
+            err.span_label(ty.span, "expected because of the type of the constant");
+        }
+        hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(_, _, ty, _), .. }) => {
+            // Point at the `Type` in `static NAME: Type = value;`.
+            err.span_label(ty.span, "expected because of the type of the static");
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::Ty(parent) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::TyKind::Array(_ty, _len) = parent.kind =>
+        {
+            // `[type; len]` in type context.
+            err.note("array length can only be `usize`");
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::Expr(parent) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::ExprKind::Repeat(_ty, _len) = parent.kind =>
+        {
+            // `[type; len]` in expr context.
+            err.note("array length can only be `usize`");
+        }
+        // FIXME: support method calls too.
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::Expr(expr) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::ExprKind::Path(path) = expr.kind
+                && let hir::QPath::Resolved(_, path) = path
+                && let Res::Def(_, def_id) = path.res =>
+        {
+            // `foo<N>()` in expression context, point at `foo`'s const parameter.
+            if let Some(i) =
+                path.segments.iter().last().and_then(|segment| segment.args).and_then(|args| {
+                    args.args.iter().position(|arg| {
+                        matches!(arg, hir::GenericArg::Const(arg) if arg.hir_id == parent.hir_id)
+                    })
+                })
+            {
+                let generics = tcx.generics_of(def_id);
+                let param = &generics.param_at(i, tcx);
+                let sp = tcx.def_span(param.def_id);
+                err.span_note(sp, "expected because of the type of the const parameter");
+            }
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::Ty(ty) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::TyKind::Path(path) = ty.kind
+                && let hir::QPath::Resolved(_, path) = path
+                && let Res::Def(_, def_id) = path.res =>
+        {
+            // `Foo<N>` in type context, point at `Foo`'s const parameter.
+            if let Some(i) =
+                path.segments.iter().last().and_then(|segment| segment.args).and_then(|args| {
+                    args.args.iter().position(|arg| {
+                        matches!(arg, hir::GenericArg::Const(arg) if arg.hir_id == parent.hir_id)
+                    })
+                })
+            {
+                let generics = tcx.generics_of(def_id);
+                let param = &generics.param_at(i, tcx);
+                let sp = tcx.def_span(param.def_id);
+                err.span_note(sp, "expected because of the type of the const parameter");
+            }
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::Variant(_variant) = tcx.parent_hir_node(anon.hir_id) =>
+        {
+            // FIXME: point at `repr` when present in the type.
+            err.note(
+                "enum variant discriminant can only be of a primitive type compatible with the \
+                 enum's `repr`",
+            );
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::GenericParam(param) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::GenericParamKind::Const { ty, .. } = param.kind =>
+        {
+            // `fn foo<const N: usize = ()>` point at the `usize`.
+            err.span_label(ty.span, "expected because of the type of the const parameter");
+        }
+        hir::Node::AnonConst(anon)
+            if let hir::Node::ConstArg(parent) = tcx.parent_hir_node(anon.hir_id)
+                && let hir::Node::TyPat(ty_pat) = tcx.parent_hir_node(parent.hir_id)
+                && let hir::Node::Ty(ty) = tcx.parent_hir_node(ty_pat.hir_id)
+                && let hir::TyKind::Pat(ty, _) = ty.kind =>
+        {
+            // Point at `char` in `pattern_type!(char is 1..=1)`.
+            err.span_label(ty.span, "the pattern must match the type");
+        }
+        _ => {}
+    }
+}
+
 fn infer_type_if_missing<'tcx>(fcx: &FnCtxt<'_, 'tcx>, node: Node<'tcx>) -> Option<Ty<'tcx>> {
     let tcx = fcx.tcx;
     let def_id = fcx.body_id;
diff --git a/tests/ui/array-slice-vec/closure-in-array-len.stderr b/tests/ui/array-slice-vec/closure-in-array-len.stderr
index decdde042c6f..04841f1d1f66 100644
--- a/tests/ui/array-slice-vec/closure-in-array-len.stderr
+++ b/tests/ui/array-slice-vec/closure-in-array-len.stderr
@@ -6,6 +6,7 @@ LL |     fn([u8; |x: u8| {}]),
    |
    = note: expected type `usize`
            found closure `{closure@$DIR/closure-in-array-len.rs:3:13: 3:20}`
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/array-slice-vec/subslice-only-once-semantic-restriction.stderr b/tests/ui/array-slice-vec/subslice-only-once-semantic-restriction.stderr
index 4d6078788b22..d665125608af 100644
--- a/tests/ui/array-slice-vec/subslice-only-once-semantic-restriction.stderr
+++ b/tests/ui/array-slice-vec/subslice-only-once-semantic-restriction.stderr
@@ -16,7 +16,9 @@ error[E0308]: mismatched types
   --> $DIR/subslice-only-once-semantic-restriction.rs:11:30
    |
 LL | const RECOVERY_WITNESS: () = 0;
-   |                              ^ expected `()`, found integer
+   |                         --   ^ expected `()`, found integer
+   |                         |
+   |                         expected because of the type of the constant
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/associated-type-bounds/suggest-contraining-assoc-type-because-of-assoc-const.stderr b/tests/ui/associated-type-bounds/suggest-contraining-assoc-type-because-of-assoc-const.stderr
index 3b89ed66b355..50bafc96acaa 100644
--- a/tests/ui/associated-type-bounds/suggest-contraining-assoc-type-because-of-assoc-const.stderr
+++ b/tests/ui/associated-type-bounds/suggest-contraining-assoc-type-because-of-assoc-const.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/suggest-contraining-assoc-type-because-of-assoc-const.rs:13:21
    |
 LL |     const N: C::M = 4u8;
-   |                     ^^^ expected associated type, found `u8`
+   |              ----   ^^^ expected associated type, found `u8`
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected associated type `<C as O>::M`
                          found type `u8`
diff --git a/tests/ui/associated-types/defaults-in-other-trait-items.rs b/tests/ui/associated-types/defaults-in-other-trait-items.rs
index 3de64e0d0db6..7b3e7f96acb5 100644
--- a/tests/ui/associated-types/defaults-in-other-trait-items.rs
+++ b/tests/ui/associated-types/defaults-in-other-trait-items.rs
@@ -37,6 +37,7 @@ trait AssocConst {
     //~^ ERROR mismatched types
     //~| NOTE expected associated type, found `u8`
     //~| NOTE expected associated type `<Self as AssocConst>::Ty`
+    //~| NOTE expected because
 }
 
 // An impl can, however
diff --git a/tests/ui/associated-types/defaults-in-other-trait-items.stderr b/tests/ui/associated-types/defaults-in-other-trait-items.stderr
index 56abd6ebf73b..fe9023e52324 100644
--- a/tests/ui/associated-types/defaults-in-other-trait-items.stderr
+++ b/tests/ui/associated-types/defaults-in-other-trait-items.stderr
@@ -19,13 +19,15 @@ LL |     type Ty = u8;
    |     ------- associated type defaults can't be assumed inside the trait defining them
 ...
 LL |     const C: Self::Ty = 0u8;
-   |                         ^^^ expected associated type, found `u8`
+   |              --------   ^^^ expected associated type, found `u8`
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected associated type `<Self as AssocConst>::Ty`
                          found type `u8`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-in-other-trait-items.rs:54:9
+  --> $DIR/defaults-in-other-trait-items.rs:55:9
    |
 LL |     type Res = isize;
    |     -------- associated type defaults can't be assumed inside the trait defining them
diff --git a/tests/ui/associated-types/issue-26681.stderr b/tests/ui/associated-types/issue-26681.stderr
index 5fb1a4ef3f5f..798f0eb392c4 100644
--- a/tests/ui/associated-types/issue-26681.stderr
+++ b/tests/ui/associated-types/issue-26681.stderr
@@ -4,7 +4,9 @@ error[E0308]: mismatched types
 LL |     type Fv: Foo = u8;
    |     ------------ associated type defaults can't be assumed inside the trait defining them
 LL |     const C: <Self::Fv as Foo>::Bar = 6665;
-   |                                       ^^^^ expected associated type, found integer
+   |              ----------------------   ^^^^ expected associated type, found integer
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected associated type `<<Self as Baz>::Fv as Foo>::Bar`
                          found type `{integer}`
diff --git a/tests/ui/closures/issue-90871.stderr b/tests/ui/closures/issue-90871.stderr
index 140f24982140..a70c761201b6 100644
--- a/tests/ui/closures/issue-90871.stderr
+++ b/tests/ui/closures/issue-90871.stderr
@@ -20,6 +20,7 @@ LL |     type_ascribe!(2, n([u8; || 1]))
    |
    = note: expected type `usize`
            found closure `{closure@$DIR/issue-90871.rs:4:29: 4:31}`
+   = note: array length can only be `usize`
 help: use parentheses to call this closure
    |
 LL |     type_ascribe!(2, n([u8; (|| 1)()]))
diff --git a/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.rs b/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.rs
index d49fb49d253c..5d6e34804c5c 100644
--- a/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.rs
+++ b/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.rs
@@ -9,6 +9,7 @@
 //~^ ERROR rustc_dump_predicates
 //~| NOTE Binder { value: ConstArgHasType(T/#0, &'static [*mut u8; 3_usize]), bound_vars: [] }
 //~| NOTE Binder { value: TraitPredicate(<ConstBytes<b"AAA"> as std::marker::Sized>, polarity:Positive), bound_vars: [] }
+//~| NOTE expected because of the type of the const parameter
 
 where
     ConstBytes<b"AAA">: Sized;
diff --git a/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.stderr b/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.stderr
index 1273a74102a2..34c65af7cd97 100644
--- a/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.stderr
+++ b/tests/ui/const-generics/adt_const_params/byte-string-u8-validation.stderr
@@ -1,11 +1,16 @@
 error[E0308]: mismatched types
-  --> $DIR/byte-string-u8-validation.rs:14:16
+  --> $DIR/byte-string-u8-validation.rs:15:16
    |
 LL |     ConstBytes<b"AAA">: Sized;
    |                ^^^^^^ expected `&[*mut u8; 3]`, found `&[u8; 3]`
    |
    = note: expected reference `&'static [*mut u8; 3]`
               found reference `&'static [u8; 3]`
+note: expected because of the type of the const parameter
+  --> $DIR/byte-string-u8-validation.rs:8:19
+   |
+LL | struct ConstBytes<const T: &'static [*mut u8; 3]>
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: rustc_dump_predicates
   --> $DIR/byte-string-u8-validation.rs:8:1
diff --git a/tests/ui/const-generics/adt_const_params/mismatch-raw-ptr-in-adt.stderr b/tests/ui/const-generics/adt_const_params/mismatch-raw-ptr-in-adt.stderr
index d7eec45bae0f..14afd18f82a7 100644
--- a/tests/ui/const-generics/adt_const_params/mismatch-raw-ptr-in-adt.stderr
+++ b/tests/ui/const-generics/adt_const_params/mismatch-raw-ptr-in-adt.stderr
@@ -15,6 +15,11 @@ LL |     let _: ConstBytes<b"AAA"> = ConstBytes::<b"BBB">;
    |
    = note: expected reference `&'static [*mut u8; 3]`
               found reference `&'static [u8; 3]`
+note: expected because of the type of the const parameter
+  --> $DIR/mismatch-raw-ptr-in-adt.rs:5:19
+   |
+LL | struct ConstBytes<const T: &'static [*mut u8; 3]>;
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/mismatch-raw-ptr-in-adt.rs:9:46
@@ -24,6 +29,11 @@ LL |     let _: ConstBytes<b"AAA"> = ConstBytes::<b"BBB">;
    |
    = note: expected reference `&'static [*mut u8; 3]`
               found reference `&'static [u8; 3]`
+note: expected because of the type of the const parameter
+  --> $DIR/mismatch-raw-ptr-in-adt.rs:5:19
+   |
+LL | struct ConstBytes<const T: &'static [*mut u8; 3]>;
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/const-generics/adt_const_params/transmutable-ice-110969.stderr b/tests/ui/const-generics/adt_const_params/transmutable-ice-110969.stderr
index 967166856147..bc8feaf5214a 100644
--- a/tests/ui/const-generics/adt_const_params/transmutable-ice-110969.stderr
+++ b/tests/ui/const-generics/adt_const_params/transmutable-ice-110969.stderr
@@ -16,7 +16,9 @@ error[E0308]: mismatched types
   --> $DIR/transmutable-ice-110969.rs:25:29
    |
 LL |         const FALSE: bool = assert::is_transmutable::<Src, Dst, Context, {}>();
-   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
+   |                      ----   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
+   |                      |
+   |                      expected because of the type of the associated constant
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.stderr b/tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.stderr
index daea55efbbc7..4125461f92b2 100644
--- a/tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.stderr
+++ b/tests/ui/const-generics/adt_const_params/unsized-anon-const-err-1.stderr
@@ -36,7 +36,9 @@ error[E0308]: mismatched types
   --> $DIR/unsized-anon-const-err-1.rs:8:34
    |
 LL |     const EMPTY_MATRIX: Matrix = [[0; 4]; 4];
-   |                                  ^^^^^^^^^^^ expected `[&u32]`, found `[&u32; 4]`
+   |                         ------   ^^^^^^^^^^^ expected `[&u32]`, found `[&u32; 4]`
+   |                         |
+   |                         expected because of the type of the constant
 
 error: aborting due to 5 previous errors
 
diff --git a/tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.stderr b/tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.stderr
index 14a41e87e4aa..9e22119cf87f 100644
--- a/tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.stderr
+++ b/tests/ui/const-generics/adt_const_params/unsized-anon-const-func-err.stderr
@@ -21,7 +21,9 @@ error[E0308]: mismatched types
   --> $DIR/unsized-anon-const-func-err.rs:9:22
    |
 LL | const VALUE: [u32] = [0; 4];
-   |                      ^^^^^^ expected `[u32]`, found `[u32; 4]`
+   |              -----   ^^^^^^ expected `[u32]`, found `[u32; 4]`
+   |              |
+   |              expected because of the type of the constant
 
 error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
   --> $DIR/unsized-anon-const-func-err.rs:14:12
diff --git a/tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.stderr b/tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.stderr
index d9a13976d68a..d81eeb465d6f 100644
--- a/tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.stderr
+++ b/tests/ui/const-generics/adt_const_params/unsized-anon-const-struct-err.stderr
@@ -30,7 +30,9 @@ error[E0308]: mismatched types
   --> $DIR/unsized-anon-const-struct-err.rs:6:22
    |
 LL | const VALUE: [u32] = [0; 4];
-   |                      ^^^^^^ expected `[u32]`, found `[u32; 4]`
+   |              -----   ^^^^^^ expected `[u32]`, found `[u32; 4]`
+   |              |
+   |              expected because of the type of the constant
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/const-generics/bad-generic-in-copy-impl.stderr b/tests/ui/const-generics/bad-generic-in-copy-impl.stderr
index fbd546d42fb5..c2cf80f38eca 100644
--- a/tests/ui/const-generics/bad-generic-in-copy-impl.stderr
+++ b/tests/ui/const-generics/bad-generic-in-copy-impl.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     x: [u8; SIZE],
    |             ^^^^ expected `usize`, found `u32`
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/bad-generic-in-copy-impl.rs:3:13
@@ -10,6 +12,7 @@ error[E0308]: mismatched types
 LL |     x: [u8; SIZE],
    |             ^^^^ expected `usize`, found `u32`
    |
+   = note: array length can only be `usize`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 2 previous errors
diff --git a/tests/ui/const-generics/generic_const_exprs/error_in_ty.stderr b/tests/ui/const-generics/generic_const_exprs/error_in_ty.stderr
index 58f0d31b0960..e10ea5a44b26 100644
--- a/tests/ui/const-generics/generic_const_exprs/error_in_ty.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/error_in_ty.stderr
@@ -29,12 +29,24 @@ error[E0308]: mismatched types
    |
 LL | impl A<2> {
    |        ^ expected `[usize; x]`, found integer
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/error_in_ty.rs:6:14
+   |
+LL | pub struct A<const z: [usize; x]> {}
+   |              ^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/error_in_ty.rs:16:8
    |
 LL | impl A<2> {
    |        ^ expected `[usize; x]`, found integer
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/error_in_ty.rs:6:14
+   |
+LL | pub struct A<const z: [usize; x]> {}
+   |              ^^^^^^^^^^^^^^^^^^^
 
 error[E0592]: duplicate definitions with name `B`
   --> $DIR/error_in_ty.rs:12:5
diff --git a/tests/ui/const-generics/generic_const_exprs/issue-105257.stderr b/tests/ui/const-generics/generic_const_exprs/issue-105257.stderr
index 1d0ab56519cf..c90feb404181 100644
--- a/tests/ui/const-generics/generic_const_exprs/issue-105257.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/issue-105257.stderr
@@ -14,7 +14,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-105257.rs:5:29
    |
 LL |     fn fnc<const N: usize = "">(&self) {}
-   |                             ^^ expected `usize`, found `&str`
+   |                     -----   ^^ expected `usize`, found `&str`
+   |                     |
+   |                     expected because of the type of the const parameter
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/const-generics/generic_const_exprs/opaque_type.stderr b/tests/ui/const-generics/generic_const_exprs/opaque_type.stderr
index 9f48a8563c8a..fd597cbde193 100644
--- a/tests/ui/const-generics/generic_const_exprs/opaque_type.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/opaque_type.stderr
@@ -9,6 +9,7 @@ LL |     let _: [u8; (N / 2) as Foo] = [0; (N / 2) as usize];
    |
    = note:     expected type `usize`
            found opaque type `Foo`
+   = note: array length can only be `usize`
 
 error[E0605]: non-primitive cast: `usize` as `Foo`
   --> $DIR/opaque_type.rs:11:17
diff --git a/tests/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr b/tests/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr
index df7c2a0a8629..9392a171510d 100644
--- a/tests/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr
+++ b/tests/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr
@@ -3,24 +3,48 @@ error[E0308]: mismatched types
    |
 LL |   get_flag::<false, 0xFF>();
    |                     ^^^^ expected `char`, found `u8`
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/invalid-patterns.rs:6:34
+   |
+LL | fn get_flag<const FlagSet: bool, const ShortName: char>() -> Option<char> {
+   |                                  ^^^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/invalid-patterns.rs:33:14
    |
 LL |   get_flag::<7, 'c'>();
    |              ^ expected `bool`, found integer
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/invalid-patterns.rs:6:13
+   |
+LL | fn get_flag<const FlagSet: bool, const ShortName: char>() -> Option<char> {
+   |             ^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/invalid-patterns.rs:35:14
    |
 LL |   get_flag::<42, 0x5ad>();
    |              ^^ expected `bool`, found integer
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/invalid-patterns.rs:6:13
+   |
+LL | fn get_flag<const FlagSet: bool, const ShortName: char>() -> Option<char> {
+   |             ^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
   --> $DIR/invalid-patterns.rs:35:18
    |
 LL |   get_flag::<42, 0x5ad>();
    |                  ^^^^^ expected `char`, found `u8`
+   |
+note: expected because of the type of the const parameter
+  --> $DIR/invalid-patterns.rs:6:34
+   |
+LL | fn get_flag<const FlagSet: bool, const ShortName: char>() -> Option<char> {
+   |                                  ^^^^^^^^^^^^^^^^^^^^^
 
 error[E0080]: reading memory at ALLOC0[0x0..0x4], but memory is uninitialized at [0x1..0x4], and this operation requires initialized memory
   --> $DIR/invalid-patterns.rs:40:32
diff --git a/tests/ui/const-generics/ogca/basic-fail.stderr b/tests/ui/const-generics/ogca/basic-fail.stderr
index ce4e8eb1471c..b1808deacd27 100644
--- a/tests/ui/const-generics/ogca/basic-fail.stderr
+++ b/tests/ui/const-generics/ogca/basic-fail.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/basic-fail.rs:15:30
    |
 LL | const ARR: [(); ADD1::<0>] = [(); INC::<0>];
-   |                              ^^^^^^^^^^^^^^ expected an array with a size of const { N + 1 }, found one with a size of const { N + 1 }
+   |            ---------------   ^^^^^^^^^^^^^^ expected an array with a size of const { N + 1 }, found one with a size of const { N + 1 }
+   |            |
+   |            expected because of the type of the constant
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/opaque_types.stderr b/tests/ui/const-generics/opaque_types.stderr
index f67e1c8ce699..d49a643e0d87 100644
--- a/tests/ui/const-generics/opaque_types.stderr
+++ b/tests/ui/const-generics/opaque_types.stderr
@@ -30,6 +30,11 @@ LL |     foo::<42>();
    |
    = note: expected opaque type `Foo`
                      found type `{integer}`
+note: expected because of the type of the const parameter
+  --> $DIR/opaque_types.rs:6:8
+   |
+LL | fn foo<const C: Foo>() {}
+   |        ^^^^^^^^^^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/const-generics/vec-macro-in-static-array.stderr b/tests/ui/const-generics/vec-macro-in-static-array.stderr
index 63d7b0c89fa1..ae08cad556fc 100644
--- a/tests/ui/const-generics/vec-macro-in-static-array.stderr
+++ b/tests/ui/const-generics/vec-macro-in-static-array.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/vec-macro-in-static-array.rs:5:26
    |
 LL | static VEC: [u32; 256] = vec![];
-   |                          ^^^^^^ expected `[u32; 256]`, found `Vec<_>`
+   |             ----------   ^^^^^^ expected `[u32; 256]`, found `Vec<_>`
+   |             |
+   |             expected because of the type of the static
    |
    = note: expected array `[u32; 256]`
              found struct `Vec<_>`
diff --git a/tests/ui/consts/array-literal-len-mismatch.stderr b/tests/ui/consts/array-literal-len-mismatch.stderr
index 39b8a647324b..782d059a294c 100644
--- a/tests/ui/consts/array-literal-len-mismatch.stderr
+++ b/tests/ui/consts/array-literal-len-mismatch.stderr
@@ -2,9 +2,10 @@ error[E0308]: mismatched types
   --> $DIR/array-literal-len-mismatch.rs:1:26
    |
 LL | const NUMBERS: [u8; 3] = [10, 20];
-   |                     -    ^^^^^^^^ expected an array with a size of 3, found one with a size of 2
-   |                     |
-   |                     help: consider specifying the actual array length: `2`
+   |                -------   ^^^^^^^^ expected an array with a size of 3, found one with a size of 2
+   |                |    |
+   |                |    help: consider specifying the actual array length: `2`
+   |                expected because of the type of the constant
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/consts/const-array-oob-arith.rs b/tests/ui/consts/const-array-oob-arith.rs
index 8e5c56e0ea82..97f8406a10f0 100644
--- a/tests/ui/consts/const-array-oob-arith.rs
+++ b/tests/ui/consts/const-array-oob-arith.rs
@@ -4,10 +4,12 @@
 const BONG: [i32; (ARR[0] - 41) as usize] = [5];
 const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
 //~^ ERROR: mismatched types
-//~| NOTE expected an array
+//~| NOTE: expected an array
+//~| NOTE: expected because
 const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
 //~^ ERROR: mismatched types
-//~| NOTE expected an array
+//~| NOTE: expected an array
+//~| NOTE: expected because
 
 fn main() {
     let _ = VAL;
diff --git a/tests/ui/consts/const-array-oob-arith.stderr b/tests/ui/consts/const-array-oob-arith.stderr
index d3299082aa14..d37ae5e4a7b3 100644
--- a/tests/ui/consts/const-array-oob-arith.stderr
+++ b/tests/ui/consts/const-array-oob-arith.stderr
@@ -2,17 +2,19 @@ error[E0308]: mismatched types
   --> $DIR/const-array-oob-arith.rs:5:45
    |
 LL | const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
-   |                   ----------------------    ^^^ expected an array with a size of 2, found one with a size of 1
-   |                   |
-   |                   help: consider specifying the actual array length: `1`
+   |             -----------------------------   ^^^ expected an array with a size of 2, found one with a size of 1
+   |             |     |
+   |             |     help: consider specifying the actual array length: `1`
+   |             expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-array-oob-arith.rs:8:44
+  --> $DIR/const-array-oob-arith.rs:9:44
    |
 LL | const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
-   |                  ----------------------    ^^^^^^^ expected an array with a size of 1, found one with a size of 2
-   |                  |
-   |                  help: consider specifying the actual array length: `2`
+   |            -----------------------------   ^^^^^^^ expected an array with a size of 1, found one with a size of 2
+   |            |     |
+   |            |     help: consider specifying the actual array length: `2`
+   |            expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/consts/const-eval/array-len-mismatch-type.stderr b/tests/ui/consts/const-eval/array-len-mismatch-type.stderr
index ce641f4a74b9..915fc8e394b3 100644
--- a/tests/ui/consts/const-eval/array-len-mismatch-type.stderr
+++ b/tests/ui/consts/const-eval/array-len-mismatch-type.stderr
@@ -4,6 +4,7 @@ error[E0308]: mismatched types
 LL | pub struct Data([[&'static str]; 5_i32]);
    |                                  ^^^^^ expected `usize`, found `i32`
    |
+   = note: array length can only be `usize`
 help: change the type of the numeric literal from `i32` to `usize`
    |
 LL - pub struct Data([[&'static str]; 5_i32]);
diff --git a/tests/ui/consts/const-eval/const-eval-span.rs b/tests/ui/consts/const-eval/const-eval-span.rs
index f1904c76b6c1..1846da22cd3d 100644
--- a/tests/ui/consts/const-eval/const-eval-span.rs
+++ b/tests/ui/consts/const-eval/const-eval-span.rs
@@ -7,8 +7,9 @@
 
 enum E {
     V = CONSTANT,
-    //~^ ERROR mismatched types
-    //~| NOTE expected `isize`, found `S`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `isize`, found `S`
+    //~| NOTE: enum variant discriminant
 }
 
 fn main() {}
diff --git a/tests/ui/consts/const-eval/const-eval-span.stderr b/tests/ui/consts/const-eval/const-eval-span.stderr
index ba11759a7106..ff17da5a04d7 100644
--- a/tests/ui/consts/const-eval/const-eval-span.stderr
+++ b/tests/ui/consts/const-eval/const-eval-span.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     V = CONSTANT,
    |         ^^^^^^^^ expected `isize`, found `S`
+   |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/consts/const-integer-bool-ops.rs b/tests/ui/consts/const-integer-bool-ops.rs
index fbbd51adfe88..e1da3e750876 100644
--- a/tests/ui/consts/const-integer-bool-ops.rs
+++ b/tests/ui/consts/const-integer-bool-ops.rs
@@ -5,6 +5,7 @@
 //~| NOTE expected `bool`, found integer
 //~| ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARR: [i32; X] = [99; 34];
 
 const X1: usize = 42 || 39;
@@ -14,6 +15,7 @@
 //~| NOTE expected `bool`, found integer
 //~| ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARR1: [i32; X1] = [99; 47];
 
 const X2: usize = -42 || -39;
@@ -23,6 +25,7 @@
 //~| NOTE expected `bool`, found integer
 //~| ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARR2: [i32; X2] = [99; 18446744073709551607];
 
 const X3: usize = -42 && -39;
@@ -32,36 +35,43 @@
 //~| NOTE expected `bool`, found integer
 //~| ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARR3: [i32; X3] = [99; 6];
 
 const Y: usize = 42.0 == 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR: [i32; Y] = [99; 1];
 
 const Y1: usize = 42.0 >= 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR1: [i32; Y1] = [99; 1];
 
 const Y2: usize = 42.0 <= 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR2: [i32; Y2] = [99; 1];
 
 const Y3: usize = 42.0 > 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR3: [i32; Y3] = [99; 0];
 
 const Y4: usize = 42.0 < 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR4: [i32; Y4] = [99; 0];
 
 const Y5: usize = 42.0 != 42.0;
 //~^ ERROR mismatched types
 //~| NOTE expected `usize`, found `bool`
+//~| NOTE expected because
 const ARRR5: [i32; Y5] = [99; 0];
 
 fn main() {
diff --git a/tests/ui/consts/const-integer-bool-ops.stderr b/tests/ui/consts/const-integer-bool-ops.stderr
index 4e503e5a5c0a..5212a5cfeb1e 100644
--- a/tests/ui/consts/const-integer-bool-ops.stderr
+++ b/tests/ui/consts/const-integer-bool-ops.stderr
@@ -14,97 +14,117 @@ error[E0308]: mismatched types
   --> $DIR/const-integer-bool-ops.rs:1:18
    |
 LL | const X: usize = 42 && 39;
-   |                  ^^^^^^^^ expected `usize`, found `bool`
+   |          -----   ^^^^^^^^ expected `usize`, found `bool`
+   |          |
+   |          expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:10:19
+  --> $DIR/const-integer-bool-ops.rs:11:19
    |
 LL | const X1: usize = 42 || 39;
    |                   ^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:10:25
+  --> $DIR/const-integer-bool-ops.rs:11:25
    |
 LL | const X1: usize = 42 || 39;
    |                         ^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:10:19
+  --> $DIR/const-integer-bool-ops.rs:11:19
    |
 LL | const X1: usize = 42 || 39;
-   |                   ^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:19:19
+  --> $DIR/const-integer-bool-ops.rs:21:19
    |
 LL | const X2: usize = -42 || -39;
    |                   ^^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:19:26
+  --> $DIR/const-integer-bool-ops.rs:21:26
    |
 LL | const X2: usize = -42 || -39;
    |                          ^^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:19:19
+  --> $DIR/const-integer-bool-ops.rs:21:19
    |
 LL | const X2: usize = -42 || -39;
-   |                   ^^^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:28:19
+  --> $DIR/const-integer-bool-ops.rs:31:19
    |
 LL | const X3: usize = -42 && -39;
    |                   ^^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:28:26
+  --> $DIR/const-integer-bool-ops.rs:31:26
    |
 LL | const X3: usize = -42 && -39;
    |                          ^^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:28:19
+  --> $DIR/const-integer-bool-ops.rs:31:19
    |
 LL | const X3: usize = -42 && -39;
-   |                   ^^^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:37:18
+  --> $DIR/const-integer-bool-ops.rs:41:18
    |
 LL | const Y: usize = 42.0 == 42.0;
-   |                  ^^^^^^^^^^^^ expected `usize`, found `bool`
-
-error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:42:19
-   |
-LL | const Y1: usize = 42.0 >= 42.0;
-   |                   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |          -----   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |          |
+   |          expected because of the type of the constant
 
 error[E0308]: mismatched types
   --> $DIR/const-integer-bool-ops.rs:47:19
    |
-LL | const Y2: usize = 42.0 <= 42.0;
-   |                   ^^^^^^^^^^^^ expected `usize`, found `bool`
+LL | const Y1: usize = 42.0 >= 42.0;
+   |           -----   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:52:19
+  --> $DIR/const-integer-bool-ops.rs:53:19
+   |
+LL | const Y2: usize = 42.0 <= 42.0;
+   |           -----   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
+
+error[E0308]: mismatched types
+  --> $DIR/const-integer-bool-ops.rs:59:19
    |
 LL | const Y3: usize = 42.0 > 42.0;
-   |                   ^^^^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:57:19
+  --> $DIR/const-integer-bool-ops.rs:65:19
    |
 LL | const Y4: usize = 42.0 < 42.0;
-   |                   ^^^^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error[E0308]: mismatched types
-  --> $DIR/const-integer-bool-ops.rs:62:19
+  --> $DIR/const-integer-bool-ops.rs:71:19
    |
 LL | const Y5: usize = 42.0 != 42.0;
-   |                   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |           -----   ^^^^^^^^^^^^ expected `usize`, found `bool`
+   |           |
+   |           expected because of the type of the constant
 
 error: aborting due to 18 previous errors
 
diff --git a/tests/ui/consts/const-result-no-expect-suggestion.stderr b/tests/ui/consts/const-result-no-expect-suggestion.stderr
index 70aa306ae3c8..337065f9f5e0 100644
--- a/tests/ui/consts/const-result-no-expect-suggestion.stderr
+++ b/tests/ui/consts/const-result-no-expect-suggestion.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/const-result-no-expect-suggestion.rs:5:19
    |
 LL | const TEST: u32 = f(2);
-   |                   ^^^^ expected `u32`, found `Result<u32, ()>`
+   |             ---   ^^^^ expected `u32`, found `Result<u32, ()>`
+   |             |
+   |             expected because of the type of the constant
    |
    = note: expected type `u32`
               found enum `Result<u32, ()>`
diff --git a/tests/ui/consts/const-slice-array-deref.stderr b/tests/ui/consts/const-slice-array-deref.stderr
index b1d069280885..e7513d01cd0e 100644
--- a/tests/ui/consts/const-slice-array-deref.stderr
+++ b/tests/ui/consts/const-slice-array-deref.stderr
@@ -11,7 +11,9 @@ error[E0308]: mismatched types
   --> $DIR/const-slice-array-deref.rs:1:20
    |
 LL | const ONE: [u16] = [1];
-   |                    ^^^ expected `[u16]`, found `[u16; 1]`
+   |            -----   ^^^ expected `[u16]`, found `[u16; 1]`
+   |            |
+   |            expected because of the type of the constant
 
 error[E0161]: cannot move a value of type `[u16]`
   --> $DIR/const-slice-array-deref.rs:5:28
diff --git a/tests/ui/consts/const-tup-index-span.rs b/tests/ui/consts/const-tup-index-span.rs
index 4cb7143b4351..6896625c3785 100644
--- a/tests/ui/consts/const-tup-index-span.rs
+++ b/tests/ui/consts/const-tup-index-span.rs
@@ -1,9 +1,10 @@
 // Test spans of errors
 
 const TUP: (usize,) = 5usize << 64;
-//~^ ERROR mismatched types
-//~| NOTE expected `(usize,)`, found `usize`
-//~| NOTE expected tuple `(usize,)`
+//~^ ERROR: mismatched types
+//~| NOTE: expected `(usize,)`, found `usize`
+//~| NOTE: expected tuple `(usize,)`
+//~| NOTE: expected because
 const ARR: [i32; TUP.0] = [];
 
 fn main() {
diff --git a/tests/ui/consts/const-tup-index-span.stderr b/tests/ui/consts/const-tup-index-span.stderr
index 792e18aa8fd4..fe4290961816 100644
--- a/tests/ui/consts/const-tup-index-span.stderr
+++ b/tests/ui/consts/const-tup-index-span.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/const-tup-index-span.rs:3:23
    |
 LL | const TUP: (usize,) = 5usize << 64;
-   |                       ^^^^^^^^^^^^ expected `(usize,)`, found `usize`
+   |            --------   ^^^^^^^^^^^^ expected `(usize,)`, found `usize`
+   |            |
+   |            expected because of the type of the constant
    |
    = note: expected tuple `(usize,)`
                found type `usize`
diff --git a/tests/ui/consts/const-type-mismatch.stderr b/tests/ui/consts/const-type-mismatch.stderr
index 17bb27d4b72f..d36ef1188f41 100644
--- a/tests/ui/consts/const-type-mismatch.stderr
+++ b/tests/ui/consts/const-type-mismatch.stderr
@@ -2,13 +2,17 @@ error[E0308]: mismatched types
   --> $DIR/const-type-mismatch.rs:4:21
    |
 LL | const TWELVE: u16 = TEN + 2;
-   |                     ^^^^^^^ expected `u16`, found `u8`
+   |               ---   ^^^^^^^ expected `u16`, found `u8`
+   |               |
+   |               expected because of the type of the constant
 
 error[E0308]: mismatched types
   --> $DIR/const-type-mismatch.rs:9:27
    |
 LL |     const ALSO_TEN: u16 = TEN;
-   |                           ^^^ expected `u16`, found `u8`
+   |                     ---   ^^^ expected `u16`, found `u8`
+   |                     |
+   |                     expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/consts/enum-discr-type-err.stderr b/tests/ui/consts/enum-discr-type-err.stderr
index 9a09d6a96f1a..c676a96ad34a 100644
--- a/tests/ui/consts/enum-discr-type-err.stderr
+++ b/tests/ui/consts/enum-discr-type-err.stderr
@@ -10,6 +10,7 @@ LL | |     B = T,
 LL | | }
    | |_- in this macro invocation
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
@@ -24,6 +25,7 @@ LL | |     B = T,
 LL | | }
    | |_- in this macro invocation
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
 
diff --git a/tests/ui/consts/issue-104768.stderr b/tests/ui/consts/issue-104768.stderr
index bd4a54de0ae4..81b4575b361b 100644
--- a/tests/ui/consts/issue-104768.stderr
+++ b/tests/ui/consts/issue-104768.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-104768.rs:1:15
    |
 LL | const A: &_ = 0_u32;
-   |               ^^^^^ expected `&_`, found `u32`
+   |          --   ^^^^^ expected `&_`, found `u32`
+   |          |
+   |          expected because of the type of the constant
    |
    = note: expected reference `&'static _`
                    found type `u32`
diff --git a/tests/ui/consts/issue-39974.rs b/tests/ui/consts/issue-39974.rs
index adc65d9be0d0..7d9f1b6cf474 100644
--- a/tests/ui/consts/issue-39974.rs
+++ b/tests/ui/consts/issue-39974.rs
@@ -1,11 +1,13 @@
 const LENGTH: f64 = 2;
-//~^ ERROR mismatched types
-//~| NOTE expected `f64`, found integer
+//~^ ERROR: mismatched types
+//~| NOTE: expected `f64`, found integer
+//~| NOTE: expected because
 
 struct Thing {
     f: [[f64; 2]; LENGTH],
-    //~^ ERROR mismatched types
-    //~| NOTE expected `usize`, found `f64`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `usize`, found `f64`
+    //~| NOTE: array length
 }
 
 fn main() {
diff --git a/tests/ui/consts/issue-39974.stderr b/tests/ui/consts/issue-39974.stderr
index 1c15debb1199..784a19445055 100644
--- a/tests/ui/consts/issue-39974.stderr
+++ b/tests/ui/consts/issue-39974.stderr
@@ -1,14 +1,18 @@
 error[E0308]: mismatched types
-  --> $DIR/issue-39974.rs:6:19
+  --> $DIR/issue-39974.rs:7:19
    |
 LL |     f: [[f64; 2]; LENGTH],
    |                   ^^^^^^ expected `usize`, found `f64`
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/issue-39974.rs:1:21
    |
 LL | const LENGTH: f64 = 2;
-   |                     ^ expected `f64`, found integer
+   |               ---   ^ expected `f64`, found integer
+   |               |
+   |               expected because of the type of the constant
    |
 help: use a float literal
    |
diff --git a/tests/ui/consts/issue-69310-array-size-lit-wrong-ty.stderr b/tests/ui/consts/issue-69310-array-size-lit-wrong-ty.stderr
index 7078b4bd7be1..1210ae87642d 100644
--- a/tests/ui/consts/issue-69310-array-size-lit-wrong-ty.stderr
+++ b/tests/ui/consts/issue-69310-array-size-lit-wrong-ty.stderr
@@ -3,12 +3,16 @@ error[E0308]: mismatched types
    |
 LL | const A: [(); 0.1] = [()];
    |               ^^^ expected `usize`, found floating-point number
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/issue-69310-array-size-lit-wrong-ty.rs:11:15
    |
 LL | const B: [(); b"a"] = [()];
    |               ^^^^ expected `usize`, found `&[u8; 1]`
+   |
+   = note: array length can only be `usize`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/consts/nested_erroneous_ctfe.stderr b/tests/ui/consts/nested_erroneous_ctfe.stderr
index db298246e7cf..b13a6dca2b38 100644
--- a/tests/ui/consts/nested_erroneous_ctfe.stderr
+++ b/tests/ui/consts/nested_erroneous_ctfe.stderr
@@ -6,6 +6,7 @@ LL |     [9; || [9; []]];
    |
    = note: expected type `usize`
              found array `[_; 0]`
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/consts/promoted-type-error-issue-133968.stderr b/tests/ui/consts/promoted-type-error-issue-133968.stderr
index 24f1268e4b6e..a6f67a2056da 100644
--- a/tests/ui/consts/promoted-type-error-issue-133968.stderr
+++ b/tests/ui/consts/promoted-type-error-issue-133968.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/promoted-type-error-issue-133968.rs:4:29
    |
 LL | static STR: &'static [u8] = "a b";
-   |                             ^^^^^ expected `&[u8]`, found `&str`
+   |             -------------   ^^^^^ expected `&[u8]`, found `&str`
+   |             |
+   |             expected because of the type of the static
    |
    = note: expected reference `&'static [u8]`
               found reference `&'static str`
diff --git a/tests/ui/diagnostic-width/long-span.long.stderr b/tests/ui/diagnostic-width/long-span.long.stderr
index 252b17912dee..526719678afe 100644
--- a/tests/ui/diagnostic-width/long-span.long.stderr
+++ b/tests/ui/diagnostic-width/long-span.long.stderr
@@ -9,8 +9,10 @@ LL │ …u8 = [0, 0, 0, 0, 0, 0, 0, 0, 0, …, 0, 0, 0, 0, 0, 0, 0] + [0, 0, 0,
 error[E0308]: mismatched types
    ╭▸ $DIR/long-span.rs:9:15
    │
-LL │ …u8 = [0, 0, 0, 0, 0, 0, 0, 0, 0, …, 0, 0, 0, 0, 0, 0, 0];
-   ╰╴      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━…━━━━━━━━━━━━━━━━━━━━━━ expected `u8`, found `[{integer}; 1680]`
+LL │ …t D: u8 = [0, 0, 0, 0, 0, 0, 0, 0… 0, 0, 0, 0, 0, 0, 0, 0, 0];
+   │       ┬─   ━━━━━━━━━━━━━━━━━━━━━━━…━━━━━━━━━━━━━━━━━━━━━━━━━━━ expected `u8`, found `[{integer}; 1680]`
+   │       │
+   ╰╴      expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/diagnostic-width/long-span.longest.stderr b/tests/ui/diagnostic-width/long-span.longest.stderr
index 2e77c3689223..0b1ca9a22fd6 100644
--- a/tests/ui/diagnostic-width/long-span.longest.stderr
+++ b/tests/ui/diagnostic-width/long-span.longest.stderr
@@ -9,8 +9,10 @@ LL | ... = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0...0, 0, 0, 0, 0, 0, 0, 0, 0
 error[E0308]: mismatched types
   --> $DIR/long-span.rs:9:15
    |
-LL | ... = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0...0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `[{integer}; 1680]`
+LL | ...D: u8 = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,..., 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
+   |       --   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `[{integer}; 1680]`
+   |       |
+   |       expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/diagnostic-width/long-span.short.stderr b/tests/ui/diagnostic-width/long-span.short.stderr
index b4803e31aaab..bd86a048c434 100644
--- a/tests/ui/diagnostic-width/long-span.short.stderr
+++ b/tests/ui/diagnostic-width/long-span.short.stderr
@@ -9,8 +9,10 @@ LL │ …u8 = [0, 0, 0…0] + [0, 0, 0…0];
 error[E0308]: mismatched types
    ╭▸ $DIR/long-span.rs:9:15
    │
-LL │ …u8 = [0, 0, 0…0];
-   ╰╴      ━━━━━━━━…━━ expected `u8`, found `[{integer}; 1680]`
+LL │ …t D: u8 = [0,…, 0, 0];
+   │       ┬─   ━━━…━━━━━━━ expected `u8`, found `[{integer}; 1680]`
+   │       │
+   ╰╴      expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/diagnostic-width/long-span.shortest.stderr b/tests/ui/diagnostic-width/long-span.shortest.stderr
index 1de1a4acd929..4d9e413287b6 100644
--- a/tests/ui/diagnostic-width/long-span.shortest.stderr
+++ b/tests/ui/diagnostic-width/long-span.shortest.stderr
@@ -9,8 +9,10 @@ LL | ... = [0, 0, 0...0] + [0, 0, 0...0];
 error[E0308]: mismatched types
   --> $DIR/long-span.rs:9:15
    |
-LL | ... = [0, 0, 0...0];
-   |       ^^^^^^^^...^^ expected `u8`, found `[{integer}; 1680]`
+LL | ...D: u8 = [0,..., 0, 0];
+   |       --   ^^^...^^^^^^^ expected `u8`, found `[{integer}; 1680]`
+   |       |
+   |       expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/did_you_mean/brackets-to-braces-single-element.stderr b/tests/ui/did_you_mean/brackets-to-braces-single-element.stderr
index d4aeb1eee96a..83a34e2bcd07 100644
--- a/tests/ui/did_you_mean/brackets-to-braces-single-element.stderr
+++ b/tests/ui/did_you_mean/brackets-to-braces-single-element.stderr
@@ -14,7 +14,9 @@ error[E0308]: mismatched types
   --> $DIR/brackets-to-braces-single-element.rs:4:19
    |
 LL | const B: &[u32] = &{ 1 };
-   |                   ^^^^^^ expected `&[u32]`, found `&{integer}`
+   |          ------   ^^^^^^ expected `&[u32]`, found `&{integer}`
+   |          |
+   |          expected because of the type of the constant
    |
    = note: expected reference `&'static [u32]`
               found reference `&{integer}`
diff --git a/tests/ui/enum-discriminant/discriminant-ill-typed.rs b/tests/ui/enum-discriminant/discriminant-ill-typed.rs
index e3cbd01a1ddf..1e456425cdd8 100644
--- a/tests/ui/enum-discriminant/discriminant-ill-typed.rs
+++ b/tests/ui/enum-discriminant/discriminant-ill-typed.rs
@@ -13,8 +13,9 @@ enum A {
         Ok = i8::MAX - 1,
         Ok2,
         OhNo = 0_u8,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `i8`, found `u8`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `i8`, found `u8`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -26,8 +27,9 @@ enum A {
         Ok = u8::MAX - 1,
         Ok2,
         OhNo = 0_i8,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `u8`, found `i8`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `u8`, found `i8`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -39,8 +41,9 @@ enum A {
         Ok = i16::MAX - 1,
         Ok2,
         OhNo = 0_u16,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `i16`, found `u16`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `i16`, found `u16`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -52,8 +55,9 @@ enum A {
         Ok = u16::MAX - 1,
         Ok2,
         OhNo = 0_i16,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `u16`, found `i16`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `u16`, found `i16`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -65,8 +69,9 @@ enum A {
         Ok = i32::MAX - 1,
         Ok2,
         OhNo = 0_u32,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `i32`, found `u32`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `i32`, found `u32`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -78,8 +83,9 @@ enum A {
         Ok = u32::MAX - 1,
         Ok2,
         OhNo = 0_i32,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `u32`, found `i32`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `u32`, found `i32`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -91,8 +97,9 @@ enum A {
         Ok = i64::MAX - 1,
         Ok2,
         OhNo = 0_u64,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `i64`, found `u64`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `i64`, found `u64`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
@@ -104,8 +111,9 @@ enum A {
         Ok = u64::MAX - 1,
         Ok2,
         OhNo = 0_i64,
-        //~^ ERROR mismatched types
-        //~| NOTE expected `u64`, found `i64`
+        //~^ ERROR: mismatched types
+        //~| NOTE: expected `u64`, found `i64`
+        //~| NOTE: enum variant discriminant
     }
 
     let x = A::Ok;
diff --git a/tests/ui/enum-discriminant/discriminant-ill-typed.stderr b/tests/ui/enum-discriminant/discriminant-ill-typed.stderr
index e9508b7fe962..794447295320 100644
--- a/tests/ui/enum-discriminant/discriminant-ill-typed.stderr
+++ b/tests/ui/enum-discriminant/discriminant-ill-typed.stderr
@@ -4,6 +4,7 @@ error[E0308]: mismatched types
 LL |         OhNo = 0_u8,
    |                ^^^^ expected `i8`, found `u8`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `u8` to `i8`
    |
 LL -         OhNo = 0_u8,
@@ -11,11 +12,12 @@ LL +         OhNo = 0_i8,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:28:16
+  --> $DIR/discriminant-ill-typed.rs:29:16
    |
 LL |         OhNo = 0_i8,
    |                ^^^^ expected `u8`, found `i8`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `i8` to `u8`
    |
 LL -         OhNo = 0_i8,
@@ -23,11 +25,12 @@ LL +         OhNo = 0_u8,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:41:16
+  --> $DIR/discriminant-ill-typed.rs:43:16
    |
 LL |         OhNo = 0_u16,
    |                ^^^^^ expected `i16`, found `u16`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `u16` to `i16`
    |
 LL -         OhNo = 0_u16,
@@ -35,11 +38,12 @@ LL +         OhNo = 0_i16,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:54:16
+  --> $DIR/discriminant-ill-typed.rs:57:16
    |
 LL |         OhNo = 0_i16,
    |                ^^^^^ expected `u16`, found `i16`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `i16` to `u16`
    |
 LL -         OhNo = 0_i16,
@@ -47,11 +51,12 @@ LL +         OhNo = 0_u16,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:67:16
+  --> $DIR/discriminant-ill-typed.rs:71:16
    |
 LL |         OhNo = 0_u32,
    |                ^^^^^ expected `i32`, found `u32`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `u32` to `i32`
    |
 LL -         OhNo = 0_u32,
@@ -59,11 +64,12 @@ LL +         OhNo = 0_i32,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:80:16
+  --> $DIR/discriminant-ill-typed.rs:85:16
    |
 LL |         OhNo = 0_i32,
    |                ^^^^^ expected `u32`, found `i32`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `i32` to `u32`
    |
 LL -         OhNo = 0_i32,
@@ -71,11 +77,12 @@ LL +         OhNo = 0_u32,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:93:16
+  --> $DIR/discriminant-ill-typed.rs:99:16
    |
 LL |         OhNo = 0_u64,
    |                ^^^^^ expected `i64`, found `u64`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `u64` to `i64`
    |
 LL -         OhNo = 0_u64,
@@ -83,11 +90,12 @@ LL +         OhNo = 0_i64,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/discriminant-ill-typed.rs:106:16
+  --> $DIR/discriminant-ill-typed.rs:113:16
    |
 LL |         OhNo = 0_i64,
    |                ^^^^^ expected `u64`, found `i64`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `i64` to `u64`
    |
 LL -         OhNo = 0_i64,
diff --git a/tests/ui/enum/closure-in-enum-issue-48838.stderr b/tests/ui/enum/closure-in-enum-issue-48838.stderr
index 17e6c3433343..6c84efe73e42 100644
--- a/tests/ui/enum/closure-in-enum-issue-48838.stderr
+++ b/tests/ui/enum/closure-in-enum-issue-48838.stderr
@@ -6,6 +6,7 @@ LL |     Square = |x| x,
    |
    = note: expected type `isize`
            found closure `{closure@$DIR/closure-in-enum-issue-48838.rs:2:14: 2:17}`
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/enum/enum-discriminant-type-mismatch-8761.rs b/tests/ui/enum/enum-discriminant-type-mismatch-8761.rs
index ae09b919dc15..63973be83774 100644
--- a/tests/ui/enum/enum-discriminant-type-mismatch-8761.rs
+++ b/tests/ui/enum/enum-discriminant-type-mismatch-8761.rs
@@ -1,11 +1,13 @@
 // https://github.com/rust-lang/rust/issues/8761
 enum Foo {
     A = 1i64,
-    //~^ ERROR mismatched types
-    //~| NOTE expected `isize`, found `i64`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `isize`, found `i64`
+    //~| NOTE: enum variant discriminant
     B = 2u8
-    //~^ ERROR mismatched types
-    //~| NOTE expected `isize`, found `u8`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `isize`, found `u8`
+    //~| NOTE: enum variant discriminant
 }
 
 fn main() {}
diff --git a/tests/ui/enum/enum-discriminant-type-mismatch-8761.stderr b/tests/ui/enum/enum-discriminant-type-mismatch-8761.stderr
index f1645183e176..d256a2ed644b 100644
--- a/tests/ui/enum/enum-discriminant-type-mismatch-8761.stderr
+++ b/tests/ui/enum/enum-discriminant-type-mismatch-8761.stderr
@@ -4,6 +4,7 @@ error[E0308]: mismatched types
 LL |     A = 1i64,
    |         ^^^^ expected `isize`, found `i64`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `i64` to `isize`
    |
 LL -     A = 1i64,
@@ -11,11 +12,12 @@ LL +     A = 1isize,
    |
 
 error[E0308]: mismatched types
-  --> $DIR/enum-discriminant-type-mismatch-8761.rs:6:9
+  --> $DIR/enum-discriminant-type-mismatch-8761.rs:7:9
    |
 LL |     B = 2u8
    |         ^^^ expected `isize`, found `u8`
    |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 help: change the type of the numeric literal from `u8` to `isize`
    |
 LL -     B = 2u8
diff --git a/tests/ui/generic-const-items/assoc-const-missing-type.stderr b/tests/ui/generic-const-items/assoc-const-missing-type.stderr
index 7c79133d64ec..b7fb625a9ea5 100644
--- a/tests/ui/generic-const-items/assoc-const-missing-type.stderr
+++ b/tests/ui/generic-const-items/assoc-const-missing-type.stderr
@@ -2,8 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/assoc-const-missing-type.rs:12:18
    |
 LL |     const K<T> = ();
-   |             -    ^^ expected type parameter `T`, found `()`
-   |             |
+   |             - -  ^^ expected type parameter `T`, found `()`
+   |             | |
+   |             | expected because of the type of the associated constant
    |             expected this type parameter
    |
    = note: expected type parameter `T`
diff --git a/tests/ui/generics/generic-struct-self-unconstrained-inference-vars-69306.stderr b/tests/ui/generics/generic-struct-self-unconstrained-inference-vars-69306.stderr
index f2fd4340a580..8bc0f0a5e92f 100644
--- a/tests/ui/generics/generic-struct-self-unconstrained-inference-vars-69306.stderr
+++ b/tests/ui/generics/generic-struct-self-unconstrained-inference-vars-69306.stderr
@@ -22,7 +22,9 @@ error[E0308]: mismatched types
 LL | impl<T> S0<T> {
    |      - found this type parameter
 LL |     const C: S0<u8> = Self(0);
-   |                       ^^^^^^^ expected `S0<u8>`, found `S0<T>`
+   |              ------   ^^^^^^^ expected `S0<u8>`, found `S0<T>`
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected struct `S0<u8>`
               found struct `S0<T>`
@@ -89,7 +91,9 @@ error[E0308]: mismatched types
 LL | impl<T> S1<T, u8> {
    |      - found this type parameter
 LL |     const C: S1<u8, u8> = Self(0, 1);
-   |                           ^^^^^^^^^^ expected `S1<u8, u8>`, found `S1<T, u8>`
+   |              ----------   ^^^^^^^^^^ expected `S1<u8, u8>`, found `S1<T, u8>`
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected struct `S1<u8, _>`
               found struct `S1<T, _>`
diff --git a/tests/ui/issues/issue-31910.rs b/tests/ui/issues/issue-31910.rs
index fc82fda0ccd8..697bbf6fe6d1 100644
--- a/tests/ui/issues/issue-31910.rs
+++ b/tests/ui/issues/issue-31910.rs
@@ -1,9 +1,10 @@
 enum Enum<T: Trait> {
-    //~^ ERROR `T` is never used
-    //~| NOTE unused type parameter
+    //~^ ERROR: `T` is never used
+    //~| NOTE: unused type parameter
     X = Trait::Number,
-    //~^ ERROR mismatched types
-    //~| NOTE expected `isize`, found `i32`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `isize`, found `i32`
+    //~| NOTE: enum variant discriminant
 }
 
 trait Trait {
diff --git a/tests/ui/issues/issue-31910.stderr b/tests/ui/issues/issue-31910.stderr
index 56e4cee53d63..765db15e8285 100644
--- a/tests/ui/issues/issue-31910.stderr
+++ b/tests/ui/issues/issue-31910.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     X = Trait::Number,
    |         ^^^^^^^^^^^^^ expected `isize`, found `i32`
+   |
+   = note: enum variant discriminant can only be of a primitive type compatible with the enum's `repr`
 
 error[E0392]: type parameter `T` is never used
   --> $DIR/issue-31910.rs:1:11
diff --git a/tests/ui/lifetimes/unusual-rib-combinations.stderr b/tests/ui/lifetimes/unusual-rib-combinations.stderr
index 7f44ab2ed6b4..1ce50903ff10 100644
--- a/tests/ui/lifetimes/unusual-rib-combinations.stderr
+++ b/tests/ui/lifetimes/unusual-rib-combinations.stderr
@@ -37,6 +37,8 @@ error[E0308]: mismatched types
    |
 LL | fn a() -> [u8; foo()] {
    |                ^^^^^ expected `usize`, found `()`
+   |
+   = note: array length can only be `usize`
 
 error: aborting due to 6 previous errors
 
diff --git a/tests/ui/mismatched_types/array-len-is-closure.stderr b/tests/ui/mismatched_types/array-len-is-closure.stderr
index db5d801871bc..a6f9518c3e63 100644
--- a/tests/ui/mismatched_types/array-len-is-closure.stderr
+++ b/tests/ui/mismatched_types/array-len-is-closure.stderr
@@ -6,6 +6,7 @@ LL |     [1; || {}];
    |
    = note: expected type `usize`
            found closure `{closure@$DIR/array-len-is-closure.rs:4:9: 4:11}`
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/mismatched_types/array-repeat-unit-struct.rs b/tests/ui/mismatched_types/array-repeat-unit-struct.rs
index db05e1daedbd..f92f97ed587b 100644
--- a/tests/ui/mismatched_types/array-repeat-unit-struct.rs
+++ b/tests/ui/mismatched_types/array-repeat-unit-struct.rs
@@ -4,6 +4,7 @@
 
 fn main() {
     let b = [0; S];
-    //~^ ERROR mismatched types
-    //~| NOTE expected `usize`, found `S`
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected `usize`, found `S`
+    //~| NOTE: array length
 }
diff --git a/tests/ui/mismatched_types/array-repeat-unit-struct.stderr b/tests/ui/mismatched_types/array-repeat-unit-struct.stderr
index 9a9cc946f82a..155adb5363a2 100644
--- a/tests/ui/mismatched_types/array-repeat-unit-struct.stderr
+++ b/tests/ui/mismatched_types/array-repeat-unit-struct.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     let b = [0; S];
    |                 ^ expected `usize`, found `S`
+   |
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/never_type/regress/loop-in-array-length.stderr b/tests/ui/never_type/regress/loop-in-array-length.stderr
index a51eb46fb244..fc0a670d08dc 100644
--- a/tests/ui/never_type/regress/loop-in-array-length.stderr
+++ b/tests/ui/never_type/regress/loop-in-array-length.stderr
@@ -14,6 +14,7 @@ LL |     [(); & { loop { continue } } ];
    |
    = note:   expected type `usize`
            found reference `&_`
+   = note: array length can only be `usize`
 help: consider removing the borrow
    |
 LL -     [(); & { loop { continue } } ];
diff --git a/tests/ui/numeric/const-scope.stderr b/tests/ui/numeric/const-scope.stderr
index 2c8d4da9d218..4851a20fcf0e 100644
--- a/tests/ui/numeric/const-scope.stderr
+++ b/tests/ui/numeric/const-scope.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/const-scope.rs:1:16
    |
 LL | const C: i32 = 1i8;
-   |                ^^^ expected `i32`, found `i8`
+   |          ---   ^^^ expected `i32`, found `i8`
+   |          |
+   |          expected because of the type of the constant
    |
 help: change the type of the numeric literal from `i8` to `i32`
    |
@@ -14,7 +16,9 @@ error[E0308]: mismatched types
   --> $DIR/const-scope.rs:2:15
    |
 LL | const D: i8 = C;
-   |               ^ expected `i8`, found `i32`
+   |          --   ^ expected `i8`, found `i32`
+   |          |
+   |          expected because of the type of the constant
 
 error[E0308]: mismatched types
   --> $DIR/const-scope.rs:5:18
diff --git a/tests/ui/parser/pat-lt-bracket-6.stderr b/tests/ui/parser/pat-lt-bracket-6.stderr
index 83c88d1085ef..6f91967b8b82 100644
--- a/tests/ui/parser/pat-lt-bracket-6.stderr
+++ b/tests/ui/parser/pat-lt-bracket-6.stderr
@@ -24,7 +24,9 @@ error[E0308]: mismatched types
   --> $DIR/pat-lt-bracket-6.rs:10:30
    |
 LL | const RECOVERY_WITNESS: () = 0;
-   |                              ^ expected `()`, found integer
+   |                         --   ^ expected `()`, found integer
+   |                         |
+   |                         expected because of the type of the constant
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/parser/pat-lt-bracket-7.stderr b/tests/ui/parser/pat-lt-bracket-7.stderr
index cc457a4e64e2..5cdb94cb8176 100644
--- a/tests/ui/parser/pat-lt-bracket-7.stderr
+++ b/tests/ui/parser/pat-lt-bracket-7.stderr
@@ -11,7 +11,9 @@ error[E0308]: mismatched types
   --> $DIR/pat-lt-bracket-7.rs:9:30
    |
 LL | const RECOVERY_WITNESS: () = 0;
-   |                              ^ expected `()`, found integer
+   |                         --   ^ expected `()`, found integer
+   |                         |
+   |                         expected because of the type of the constant
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/parser/recover/recover-for-loop-parens-around-head.stderr b/tests/ui/parser/recover/recover-for-loop-parens-around-head.stderr
index 2bc7952def79..8b784d02a01d 100644
--- a/tests/ui/parser/recover/recover-for-loop-parens-around-head.stderr
+++ b/tests/ui/parser/recover/recover-for-loop-parens-around-head.stderr
@@ -14,7 +14,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-for-loop-parens-around-head.rs:13:40
    |
 LL |         const _RECOVERY_WITNESS: u32 = 0u8;
-   |                                        ^^^ expected `u32`, found `u8`
+   |                                  ---   ^^^ expected `u32`, found `u8`
+   |                                  |
+   |                                  expected because of the type of the constant
    |
 help: change the type of the numeric literal from `u8` to `u32`
    |
diff --git a/tests/ui/proc-macro/macro-brackets.stderr b/tests/ui/proc-macro/macro-brackets.stderr
index f14b5fed6b9e..00c1c6b0f4cf 100644
--- a/tests/ui/proc-macro/macro-brackets.stderr
+++ b/tests/ui/proc-macro/macro-brackets.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/macro-brackets.rs:11:21
    |
 LL | id![static X: u32 = 'a';];
-   |                     ^^^ expected `u32`, found `char`
+   |               ---   ^^^ expected `u32`, found `char`
+   |               |
+   |               expected because of the type of the static
    |
 help: you can cast a `char` to a `u32`, since a `char` always occupies 4 bytes
    |
diff --git a/tests/ui/repeat-expr/repeat_count.stderr b/tests/ui/repeat-expr/repeat_count.stderr
index eb9581b8f7ae..e2cecf9973b8 100644
--- a/tests/ui/repeat-expr/repeat_count.stderr
+++ b/tests/ui/repeat-expr/repeat_count.stderr
@@ -15,24 +15,32 @@ error[E0308]: mismatched types
    |
 LL |     let b = [0; ()];
    |                 ^^ expected `usize`, found `()`
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:12:17
    |
 LL |     let c = [0; true];
    |                 ^^^^ expected `usize`, found `bool`
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:15:17
    |
 LL |     let d = [0; 0.5];
    |                 ^^^ expected `usize`, found floating-point number
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:18:17
    |
 LL |     let e = [0; "foo"];
    |                 ^^^^^ expected `usize`, found `&str`
+   |
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:21:17
@@ -41,6 +49,7 @@ LL |     let f = [0; -4_isize];
    |                 ^^^^^^^^ expected `usize`, found `isize`
    |
    = note: `-4_isize` cannot fit into type `usize`
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:25:23
@@ -49,6 +58,7 @@ LL |     let g = [0_usize; -1_isize];
    |                       ^^^^^^^^ expected `usize`, found `isize`
    |
    = note: `-1_isize` cannot fit into type `usize`
+   = note: array length can only be `usize`
 
 error[E0308]: mismatched types
   --> $DIR/repeat_count.rs:29:17
@@ -56,6 +66,7 @@ error[E0308]: mismatched types
 LL |     let h = [0; 4u8];
    |                 ^^^ expected `usize`, found `u8`
    |
+   = note: array length can only be `usize`
 help: change the type of the numeric literal from `u8` to `usize`
    |
 LL -     let h = [0; 4u8];
@@ -67,6 +78,8 @@ error[E0308]: mismatched types
    |
 LL |     let i = [0; I { i: () }];
    |                 ^^^^^^^^^^^ expected `usize`, found `I`
+   |
+   = note: array length can only be `usize`
 
 error: aborting due to 9 previous errors
 
diff --git a/tests/ui/self/issue-61882.stderr b/tests/ui/self/issue-61882.stderr
index 96f4e41de174..867e3e97ac37 100644
--- a/tests/ui/self/issue-61882.stderr
+++ b/tests/ui/self/issue-61882.stderr
@@ -16,7 +16,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-61882.rs:4:22
    |
 LL |     const B: A<u8> = Self(0);
-   |                      ^^^^^^^ expected `A<u8>`, found `A<bool>`
+   |              -----   ^^^^^^^ expected `A<u8>`, found `A<bool>`
+   |              |
+   |              expected because of the type of the associated constant
    |
    = note: expected struct `A<u8>`
               found struct `A<bool>`
diff --git a/tests/ui/static/bad-const-type.rs b/tests/ui/static/bad-const-type.rs
index d4e6352d7c1c..696fa295af41 100644
--- a/tests/ui/static/bad-const-type.rs
+++ b/tests/ui/static/bad-const-type.rs
@@ -1,4 +1,5 @@
 static i: String = 10;
-//~^ ERROR mismatched types
-//~| NOTE expected `String`, found integer
+//~^ ERROR: mismatched types
+//~| NOTE: expected `String`, found integer
+//~| NOTE: expected because
 fn main() { println!("{}", i); }
diff --git a/tests/ui/static/bad-const-type.stderr b/tests/ui/static/bad-const-type.stderr
index 8573a11ef291..12ecb73d94da 100644
--- a/tests/ui/static/bad-const-type.stderr
+++ b/tests/ui/static/bad-const-type.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/bad-const-type.rs:1:20
    |
 LL | static i: String = 10;
-   |                    ^^ expected `String`, found integer
+   |           ------   ^^ expected `String`, found integer
+   |           |
+   |           expected because of the type of the static
    |
 help: try using a conversion method
    |
diff --git a/tests/ui/static/issue-5216.stderr b/tests/ui/static/issue-5216.stderr
index 99c8b1aa131a..9748223e3d1d 100644
--- a/tests/ui/static/issue-5216.stderr
+++ b/tests/ui/static/issue-5216.stderr
@@ -18,7 +18,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-5216.rs:8:19
    |
 LL | pub static D: T = g;
-   |                   ^ expected `Box<dyn FnMut() + Sync>`, found fn item
+   |               -   ^ expected `Box<dyn FnMut() + Sync>`, found fn item
+   |               |
+   |               expected because of the type of the static
    |
    = note: expected struct `Box<(dyn FnMut() + Sync + 'static)>`
              found fn item `fn() {g}`
diff --git a/tests/ui/transmutability/arrays/issue-103783-array-length.stderr b/tests/ui/transmutability/arrays/issue-103783-array-length.stderr
index 02ac40741cb7..18f6e9b4ed10 100644
--- a/tests/ui/transmutability/arrays/issue-103783-array-length.stderr
+++ b/tests/ui/transmutability/arrays/issue-103783-array-length.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     type NaughtyLenArray = [u32; 3.14159];
    |                                  ^^^^^^^ expected `usize`, found floating-point number
+   |
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/type/pattern_types/nested.stderr b/tests/ui/type/pattern_types/nested.stderr
index 7893cc849248..cb491a78945c 100644
--- a/tests/ui/type/pattern_types/nested.stderr
+++ b/tests/ui/type/pattern_types/nested.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/nested.rs:10:63
    |
 LL | const BAD_NESTING: pattern_type!(pattern_type!(u32 is 1..) is 0..) = todo!();
-   |                                                               ^ expected `(u32) is 1..`, found integer
+   |                                  -------------------------    ^ expected `(u32) is 1..`, found integer
+   |                                  |
+   |                                  the pattern must match the type
    |
    = note: expected pattern type `(u32) is 1..`
                       found type `{integer}`
diff --git a/tests/ui/type/pattern_types/pattern_type_mismatch.stderr b/tests/ui/type/pattern_types/pattern_type_mismatch.stderr
index 4af92a89c445..129e4b5cdc7b 100644
--- a/tests/ui/type/pattern_types/pattern_type_mismatch.stderr
+++ b/tests/ui/type/pattern_types/pattern_type_mismatch.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/pattern_type_mismatch.rs:8:41
    |
 LL | const BAD_NESTING4: pattern_type!(u8 is 'a'..='a') = todo!();
-   |                                         ^^^ expected `u8`, found `char`
+   |                                   --    ^^^ expected `u8`, found `char`
+   |                                   |
+   |                                   the pattern must match the type
    |
 help: if you meant to write a byte literal, prefix with `b`
    |
@@ -13,7 +15,9 @@ error[E0308]: mismatched types
   --> $DIR/pattern_type_mismatch.rs:8:47
    |
 LL | const BAD_NESTING4: pattern_type!(u8 is 'a'..='a') = todo!();
-   |                                               ^^^ expected `u8`, found `char`
+   |                                   --          ^^^ expected `u8`, found `char`
+   |                                   |
+   |                                   the pattern must match the type
    |
 help: if you meant to write a byte literal, prefix with `b`
    |
@@ -24,13 +28,17 @@ error[E0308]: mismatched types
   --> $DIR/pattern_type_mismatch.rs:12:43
    |
 LL | const BAD_NESTING5: pattern_type!(char is 1..=1) = todo!();
-   |                                           ^ expected `char`, found `u8`
+   |                                   ----    ^ expected `char`, found `u8`
+   |                                   |
+   |                                   the pattern must match the type
 
 error[E0308]: mismatched types
   --> $DIR/pattern_type_mismatch.rs:12:47
    |
 LL | const BAD_NESTING5: pattern_type!(char is 1..=1) = todo!();
-   |                                               ^ expected `char`, found `u8`
+   |                                   ----        ^ expected `char`, found `u8`
+   |                                   |
+   |                                   the pattern must match the type
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/wf/range-expr-root-of-constant-issue-40749.rs b/tests/ui/wf/range-expr-root-of-constant-issue-40749.rs
index bec92448d1c8..07e4b9addaa1 100644
--- a/tests/ui/wf/range-expr-root-of-constant-issue-40749.rs
+++ b/tests/ui/wf/range-expr-root-of-constant-issue-40749.rs
@@ -1,9 +1,11 @@
 fn main() {
     [0; ..10];
-    //~^ ERROR mismatched types
-    //~| NOTE expected type `usize`
-    //~| NOTE found struct `RangeTo<{integer}>`
-    //~| NOTE expected `usize`, found `RangeTo<{integer}>
-    //~| NOTE in this expansion of desugaring of range expression
-    //~| NOTE in this expansion of desugaring of range expression
+    //~^ ERROR: mismatched types
+    //~| NOTE: expected type `usize`
+    //~| NOTE: found struct `RangeTo<{integer}>`
+    //~| NOTE: expected `usize`, found `RangeTo<{integer}>
+    //~| NOTE: array length can only be `usize`
+    //~| NOTE: in this expansion of desugaring of range expression
+    //~| NOTE: in this expansion of desugaring of range expression
+    //~| NOTE: in this expansion of desugaring of range expression
 }
diff --git a/tests/ui/wf/range-expr-root-of-constant-issue-40749.stderr b/tests/ui/wf/range-expr-root-of-constant-issue-40749.stderr
index 482773a39440..daddbe9fa469 100644
--- a/tests/ui/wf/range-expr-root-of-constant-issue-40749.stderr
+++ b/tests/ui/wf/range-expr-root-of-constant-issue-40749.stderr
@@ -6,6 +6,7 @@ LL |     [0; ..10];
    |
    = note: expected type `usize`
             found struct `RangeTo<{integer}>`
+   = note: array length can only be `usize`
 
 error: aborting due to 1 previous error