suggest valid features when target feature is invalid

compiler/rustc_codegen_ssa/src/errors.rs

@@ -8,7 +8,8 @@
 
 use rustc_errors::codes::*;
 use rustc_errors::{
-    Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, IntoDiagArg, Level, msg,
+    Diag, DiagArgValue, DiagCtxtHandle, DiagSymbolList, Diagnostic, EmissionGuarantee, IntoDiagArg,
+    Level, msg,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_middle::ty::layout::LayoutError;
@@ -1249,20 +1250,29 @@ pub(crate) struct FeatureNotValid<'a> {
     #[label("`{$feature}` is not valid for this target")]
     pub span: Span,
     #[subdiagnostic]
-    pub plus_hint: Option<RemovePlusFromFeatureName<'a>>,
+    pub hint: FeatureNotValidHint<'a>,
 }
 
 #[derive(Subdiagnostic)]
-#[suggestion(
-    "consider removing the leading `+` in the feature name",
-    code = "enable = \"{stripped}\"",
-    applicability = "maybe-incorrect",
-    style = "verbose"
-)]
-pub struct RemovePlusFromFeatureName<'a> {
-    #[primary_span]
-    pub span: Span,
-    pub stripped: &'a str,
+pub(crate) enum FeatureNotValidHint<'a> {
+    #[suggestion(
+        "consider removing the leading `+` in the feature name",
+        code = "enable = \"{stripped}\"",
+        applicability = "maybe-incorrect",
+        style = "verbose"
+    )]
+    RemovePlusFromFeatureName {
+        #[primary_span]
+        span: Span,
+        stripped: &'a str,
+    },
+    #[help(
+        "valid names are: {$possibilities}{$and_more ->
+            [0] {\"\"}
+            *[other] {\" \"}and {$and_more} more
+        }"
+    )]
+    ValidFeatureNames { possibilities: DiagSymbolList<&'a str>, and_more: usize },
 }
 
 #[derive(Diagnostic)]

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -9,12 +9,12 @@
 use rustc_session::Session;
 use rustc_session::lint::builtin::AARCH64_SOFTFLOAT_NEON;
 use rustc_session::parse::feature_err;
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Span, Symbol, edit_distance, sym};
 use rustc_target::spec::Arch;
 use rustc_target::target_features::{RUSTC_SPECIFIC_FEATURES, Stability};
 use smallvec::SmallVec;
 
-use crate::errors::{FeatureNotValid, RemovePlusFromFeatureName};
+use crate::errors::{FeatureNotValid, FeatureNotValidHint};
 use crate::{errors, target_features};
 
 /// Compute the enabled target features from the `#[target_feature]` function attribute.
@@ -32,15 +32,25 @@ pub(crate) fn from_target_feature_attr(
     for &(feature, feature_span) in features {
         let feature_str = feature.as_str();
         let Some(stability) = rust_target_features.get(feature_str) else {
-            let plus_hint = feature_str
-                .strip_prefix('+')
-                .filter(|stripped| rust_target_features.contains_key(*stripped))
-                .map(|stripped| RemovePlusFromFeatureName { span: feature_span, stripped });
-            tcx.dcx().emit_err(FeatureNotValid {
-                feature: feature_str,
-                span: feature_span,
-                plus_hint,
-            });
+            let hint = if let Some(stripped) = feature_str.strip_prefix('+')
+                && rust_target_features.contains_key(stripped)
+            {
+                FeatureNotValidHint::RemovePlusFromFeatureName { span: feature_span, stripped }
+            } else {
+                // Show the 5 feature names that are most similar to the input.
+                let mut valid_names: Vec<_> =
+                    rust_target_features.keys().map(|name| name.as_str()).into_sorted_stable_ord();
+                valid_names.sort_by_key(|name| {
+                    edit_distance::edit_distance(name, feature.as_str(), 5).unwrap_or(usize::MAX)
+                });
+                valid_names.truncate(5);
+
+                FeatureNotValidHint::ValidFeatureNames {
+                    possibilities: valid_names.into(),
+                    and_more: rust_target_features.len().saturating_sub(5),
+                }
+            };
+            tcx.dcx().emit_err(FeatureNotValid { feature: feature_str, span: feature_span, hint });
             continue;
         };
 

tests/ui/target-feature/invalid-attribute.rs

@@ -119,7 +119,12 @@ fn main() {
 //~| NOTE `+sse2` is not valid for this target
 unsafe fn hey() {}
 
-#[target_feature(enable = "+sse5")]
-//~^ ERROR `+sse5` is not valid for this target
-//~| NOTE `+sse5` is not valid for this target
-unsafe fn typo() {}
+#[target_feature(enable = "sse5")]
+//~^ ERROR `sse5` is not valid for this target
+//~| NOTE `sse5` is not valid for this target
+unsafe fn typo_sse() {}
+
+#[target_feature(enable = "avx512")]
+//~^ ERROR `avx512` is not valid for this target
+//~| NOTE `avx512` is not valid for this target
+unsafe fn typo_avx512() {}

tests/ui/target-feature/invalid-attribute.stderr

@@ -160,6 +160,8 @@ error: the feature named `foo` is not valid for this target
    |
 LL | #[target_feature(enable = "foo")]
    |                  ^^^^^^^^^^^^^^ `foo` is not valid for this target
+   |
+   = help: valid names are: `fma`, `xop`, `adx`, `aes`, and `avx` and 74 more
 
 error[E0046]: not all trait items implemented, missing: `foo`
   --> $DIR/invalid-attribute.rs:81:1
@@ -205,13 +207,23 @@ LL - #[target_feature(enable = "+sse2")]
 LL + #[target_feature(enable = "sse2")]
    |
 
-error: the feature named `+sse5` is not valid for this target
+error: the feature named `sse5` is not valid for this target
   --> $DIR/invalid-attribute.rs:122:18
    |
-LL | #[target_feature(enable = "+sse5")]
-   |                  ^^^^^^^^^^^^^^^^ `+sse5` is not valid for this target
+LL | #[target_feature(enable = "sse5")]
+   |                  ^^^^^^^^^^^^^^^ `sse5` is not valid for this target
+   |
+   = help: valid names are: `sse`, `sse2`, `sse3`, `sse4a`, and `ssse3` and 74 more
 
-error: aborting due to 25 previous errors
+error: the feature named `avx512` is not valid for this target
+  --> $DIR/invalid-attribute.rs:127:18
+   |
+LL | #[target_feature(enable = "avx512")]
+   |                  ^^^^^^^^^^^^^^^^^ `avx512` is not valid for this target
+   |
+   = help: valid names are: `avx512f`, `avx2`, `avx512bw`, `avx512cd`, and `avx512dq` and 74 more
+
+error: aborting due to 26 previous errors
 
 Some errors have detailed explanations: E0046, E0053, E0539, E0658.
 For more information about an error, try `rustc --explain E0046`.