hir_analysis: check number of vectors in tuples

Introduces a new check in `rustc_hir_analysis` enforcing that tuples of
scalable vectors should only up to eight vectors.

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1489,8 +1489,17 @@ fn check_scalable_vector(tcx: TyCtxt<'_>, span: Span, def_id: LocalDefId, scalab
             return;
         }
         ScalableElt::Container if fields.is_empty() => {
-            let mut err =
-                tcx.dcx().struct_span_err(span, "scalable vectors must have a single field");
+            let mut err = tcx
+                .dcx()
+                .struct_span_err(span, "scalable vector tuples must have at least one field");
+            err.help("tuples of scalable vectors can only contain multiple of the same scalable vector type");
+            err.emit();
+            return;
+        }
+        ScalableElt::Container if fields.len() > 8 => {
+            let mut err = tcx
+                .dcx()
+                .struct_span_err(span, "scalable vector tuples can have at most eight fields");
             err.help("tuples of scalable vectors can only contain multiple of the same scalable vector type");
             err.emit();
             return;

tests/ui/scalable-vectors/illformed.rs

@@ -3,6 +3,9 @@
 #![allow(internal_features)]
 #![feature(rustc_attrs)]
 
+#[rustc_scalable_vector(4)]
+struct Valid(f32);
+
 #[rustc_scalable_vector(4)]
 struct NoFieldsStructWithElementCount {}
 //~^ ERROR: scalable vectors must have a single field
@@ -19,16 +22,16 @@ struct NoFieldsStructWithElementCount {}
 
 #[rustc_scalable_vector]
 struct NoFieldsStructWithoutElementCount {}
-//~^ ERROR: scalable vectors must have a single field
+//~^ ERROR: scalable vector tuples must have at least one field
 //~^^ ERROR: scalable vectors must be tuple structs
 
 #[rustc_scalable_vector]
 struct NoFieldsTupleWithoutElementCount();
-//~^ ERROR: scalable vectors must have a single field
+//~^ ERROR: scalable vector tuples must have at least one field
 
 #[rustc_scalable_vector]
 struct NoFieldsUnitWithoutElementCount;
-//~^ ERROR: scalable vectors must have a single field
+//~^ ERROR: scalable vector tuples must have at least one field
 //~^^ ERROR: scalable vectors must be tuple structs
 
 #[rustc_scalable_vector(4)]
@@ -58,3 +61,8 @@ struct MultipleFieldsStructWithoutElementCount {
 #[rustc_scalable_vector(2)]
 struct SingleFieldStruct { _ty: f64 }
 //~^ ERROR: scalable vectors must be tuple structs
+
+#[rustc_scalable_vector]
+struct TooManyFieldsWithoutElementCount(
+    Valid, Valid, Valid, Valid, Valid, Valid, Valid, Valid, Valid);
+//~^^ ERROR: scalable vector tuples can have at most eight fields

tests/ui/scalable-vectors/illformed.stderr

@@ -1,29 +1,29 @@
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:7:1
+  --> $DIR/illformed.rs:10:1
    |
 LL | struct NoFieldsStructWithElementCount {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:16:1
+  --> $DIR/illformed.rs:19:1
    |
 LL | struct NoFieldsUnitWithElementCount;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:21:1
+  --> $DIR/illformed.rs:24:1
    |
 LL | struct NoFieldsStructWithoutElementCount {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:30:1
+  --> $DIR/illformed.rs:33:1
    |
 LL | struct NoFieldsUnitWithoutElementCount;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:35:1
+  --> $DIR/illformed.rs:38:1
    |
 LL | / struct MultipleFieldsStructWithElementCount {
 LL | |
@@ -34,7 +34,7 @@ LL | | }
    | |_^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:47:1
+  --> $DIR/illformed.rs:50:1
    |
 LL | / struct MultipleFieldsStructWithoutElementCount {
 LL | |
@@ -44,13 +44,13 @@ LL | | }
    | |_^
 
 error: scalable vectors must be tuple structs
-  --> $DIR/illformed.rs:59:1
+  --> $DIR/illformed.rs:62:1
    |
 LL | struct SingleFieldStruct { _ty: f64 }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:7:1
+  --> $DIR/illformed.rs:10:1
    |
 LL | struct NoFieldsStructWithElementCount {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -58,7 +58,7 @@ LL | struct NoFieldsStructWithElementCount {}
    = help: scalable vector types' only field must be a primitive scalar type
 
 error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:12:1
+  --> $DIR/illformed.rs:15:1
    |
 LL | struct NoFieldsTupleWithElementCount();
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -66,31 +66,31 @@ LL | struct NoFieldsTupleWithElementCount();
    = help: scalable vector types' only field must be a primitive scalar type
 
 error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:16:1
+  --> $DIR/illformed.rs:19:1
    |
 LL | struct NoFieldsUnitWithElementCount;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: scalable vector types' only field must be a primitive scalar type
 
-error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:21:1
+error: scalable vector tuples must have at least one field
+  --> $DIR/illformed.rs:24:1
    |
 LL | struct NoFieldsStructWithoutElementCount {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: tuples of scalable vectors can only contain multiple of the same scalable vector type
 
-error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:26:1
+error: scalable vector tuples must have at least one field
+  --> $DIR/illformed.rs:29:1
    |
 LL | struct NoFieldsTupleWithoutElementCount();
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: tuples of scalable vectors can only contain multiple of the same scalable vector type
 
-error: scalable vectors must have a single field
-  --> $DIR/illformed.rs:30:1
+error: scalable vector tuples must have at least one field
+  --> $DIR/illformed.rs:33:1
    |
 LL | struct NoFieldsUnitWithoutElementCount;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -98,28 +98,36 @@ LL | struct NoFieldsUnitWithoutElementCount;
    = help: tuples of scalable vectors can only contain multiple of the same scalable vector type
 
 error: scalable vectors cannot have multiple fields
-  --> $DIR/illformed.rs:35:1
+  --> $DIR/illformed.rs:38:1
    |
 LL | struct MultipleFieldsStructWithElementCount {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vectors cannot have multiple fields
-  --> $DIR/illformed.rs:43:1
+  --> $DIR/illformed.rs:46:1
    |
 LL | struct MultipleFieldsTupleWithElementCount(f32, u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: scalable vector structs can only have scalable vector fields
-  --> $DIR/illformed.rs:49:5
+  --> $DIR/illformed.rs:52:5
    |
 LL |     _ty: f32,
    |     ^^^^^^^^
 
 error: scalable vector structs can only have scalable vector fields
-  --> $DIR/illformed.rs:55:47
+  --> $DIR/illformed.rs:58:47
    |
 LL | struct MultipleFieldsTupleWithoutElementCount(f32, u32);
    |                                               ^^^
 
-error: aborting due to 17 previous errors
+error: scalable vector tuples can have at most eight fields
+  --> $DIR/illformed.rs:66:1
+   |
+LL | struct TooManyFieldsWithoutElementCount(
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: tuples of scalable vectors can only contain multiple of the same scalable vector type
+
+error: aborting due to 18 previous errors