Generalize E0401

Author: fmease

compiler/rustc_error_codes/src/error_codes/E0401.md

@@ -1,4 +1,4 @@
-Inner items do not inherit type or const parameters from the functions
+Inner items do not inherit the generic parameters from the items
 they are embedded in.
 
 Erroneous code example:
@@ -32,8 +32,8 @@ fn foo<T>(x: T) {
 }
 ```
 
-Items inside functions are basically just like top-level items, except
-that they can only be used from the function they are in.
+Items nested inside other items are basically just like top-level items, except
+that they can only be used from the item they are in.
 
 There are a couple of solutions for this.
 

compiler/rustc_resolve/src/diagnostics.rs

@@ -553,14 +553,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         resolution_error: ResolutionError<'a>,
     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
         match resolution_error {
-            ResolutionError::GenericParamsFromOuterFunction(outer_res, has_generic_params) => {
+            ResolutionError::GenericParamsFromOuterItem(outer_res, has_generic_params) => {
                 let mut err = struct_span_err!(
                     self.tcx.sess,
                     span,
                     E0401,
-                    "can't use generic parameters from outer function",
+                    "can't use generic parameters from outer item",
                 );
-                err.span_label(span, "use of generic parameter from outer function");
+                err.span_label(span, "use of generic parameter from outer item");
 
                 let sm = self.tcx.sess.source_map();
                 let def_id = match outer_res {
@@ -573,33 +573,28 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             reduce_impl_span_to_impl_keyword(sm, self.def_span(def_id)),
                             "`Self` type implicitly declared here, by this `impl`",
                         );
-                        err.span_label(span, "use a type here instead");
+                        err.span_label(span, "refer to the type directly here instead");
                         return err;
                     }
                     Res::Def(DefKind::TyParam, def_id) => {
-                        err.span_label(self.def_span(def_id), "type parameter from outer function");
+                        err.span_label(self.def_span(def_id), "type parameter from outer item");
                         def_id
                     }
                     Res::Def(DefKind::ConstParam, def_id) => {
-                        err.span_label(
-                            self.def_span(def_id),
-                            "const parameter from outer function",
-                        );
+                        err.span_label(self.def_span(def_id), "const parameter from outer item");
                         def_id
                     }
                     _ => {
                         bug!(
-                            "GenericParamsFromOuterFunction should only be used with \
+                            "GenericParamsFromOuterItem should only be used with \
                             Res::SelfTyParam, Res::SelfTyAlias, DefKind::TyParam or \
                             DefKind::ConstParam"
                         );
                     }
                 };
 
                 if let HasGenericParams::Yes(span) = has_generic_params {
-                    // Try to retrieve the span of the function signature and generate a new
-                    // message with a local type or const parameter.
-                    let sugg_msg = "try using a local generic parameter instead";
+                    let sugg_msg = "try introducing a local generic parameter here";
                     let name = self.tcx.item_name(def_id);
                     let (span, snippet) = if span.is_empty() {
                         let snippet = format!("<{name}>");
@@ -609,7 +604,6 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         let snippet = format!("{name}, ");
                         (span, snippet)
                     };
-                    // Suggest the modification to the user
                     err.span_suggestion(span, sugg_msg, snippet, Applicability::MaybeIncorrect);
                 }
 

compiler/rustc_resolve/src/ident.rs

@@ -1229,10 +1229,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     if let Some(span) = finalize {
                         self.report_error(
                             span,
-                            ResolutionError::GenericParamsFromOuterFunction(
-                                res,
-                                has_generic_params,
-                            ),
+                            ResolutionError::GenericParamsFromOuterItem(res, has_generic_params),
                         );
                     }
                     return Res::Err;
@@ -1296,10 +1293,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     if let Some(span) = finalize {
                         self.report_error(
                             span,
-                            ResolutionError::GenericParamsFromOuterFunction(
-                                res,
-                                has_generic_params,
-                            ),
+                            ResolutionError::GenericParamsFromOuterItem(res, has_generic_params),
                         );
                     }
                     return Res::Err;

compiler/rustc_resolve/src/lib.rs

@@ -186,8 +186,8 @@ struct BindingError {
 
 #[derive(Debug)]
 enum ResolutionError<'a> {
-    /// Error E0401: can't use type or const parameters from outer function.
-    GenericParamsFromOuterFunction(Res, HasGenericParams),
+    /// Error E0401: can't use type or const parameters from outer item.
+    GenericParamsFromOuterItem(Res, HasGenericParams),
     /// Error E0403: the name is already used for a type or const parameter in this generic
     /// parameter list.
     NameAlreadyUsedInParameterList(Symbol, Span),

tests/ui/const-generics/early/const-param-from-outer-fn.rs

@@ -1,6 +1,6 @@
 fn foo<const X: u32>() {
     fn bar() -> u32 {
-        X //~ ERROR can't use generic parameters from outer function
+        X //~ ERROR can't use generic parameters from outer item
     }
 }
 

tests/ui/const-generics/early/const-param-from-outer-fn.stderr

@@ -1,12 +1,12 @@
-error[E0401]: can't use generic parameters from outer function
+error[E0401]: can't use generic parameters from outer item
   --> $DIR/const-param-from-outer-fn.rs:3:9
    |
 LL | fn foo<const X: u32>() {
-   |              - const parameter from outer function
+   |              - const parameter from outer item
 LL |     fn bar() -> u32 {
-   |           - help: try using a local generic parameter instead: `<X>`
+   |           - help: try introducing a local generic parameter here: `<X>`
 LL |         X
-   |         ^ use of generic parameter from outer function
+   |         ^ use of generic parameter from outer item
 
 error: aborting due to previous error
 

tests/ui/error-codes/E0401.stderr

@@ -1,26 +1,26 @@
-error[E0401]: can't use generic parameters from outer function
+error[E0401]: can't use generic parameters from outer item
   --> $DIR/E0401.rs:4:39
    |
 LL | fn foo<T>(x: T) {
-   |        - type parameter from outer function
+   |        - type parameter from outer item
 LL |     fn bfnr<U, V: Baz<U>, W: Fn()>(y: T) {
-   |             -                         ^ use of generic parameter from outer function
+   |             -                         ^ use of generic parameter from outer item
    |             |
-   |             help: try using a local generic parameter instead: `T,`
+   |             help: try introducing a local generic parameter here: `T,`
 
-error[E0401]: can't use generic parameters from outer function
+error[E0401]: can't use generic parameters from outer item
   --> $DIR/E0401.rs:9:16
    |
 LL | fn foo<T>(x: T) {
-   |        - type parameter from outer function
+   |        - type parameter from outer item
 ...
 LL |     fn baz<U,
-   |            - help: try using a local generic parameter instead: `T,`
+   |            - help: try introducing a local generic parameter here: `T,`
 ...
 LL |            (y: T) {
-   |                ^ use of generic parameter from outer function
+   |                ^ use of generic parameter from outer item
 
-error[E0401]: can't use generic parameters from outer function
+error[E0401]: can't use generic parameters from outer item
   --> $DIR/E0401.rs:24:25
    |
 LL | impl<T> Iterator for A<T> {
@@ -29,8 +29,8 @@ LL | impl<T> Iterator for A<T> {
 LL |         fn helper(sel: &Self) -> u8 {
    |                         ^^^^
    |                         |
-   |                         use of generic parameter from outer function
-   |                         use a type here instead
+   |                         use of generic parameter from outer item
+   |                         refer to the type directly here instead
 
 error[E0282]: type annotations needed
   --> $DIR/E0401.rs:11:5

tests/ui/generics/issue-94432-garbage-ice.rs

@@ -4,7 +4,7 @@
 
 fn�a<e>(){fn�p(){e}} //~ ERROR unknown start of token: \u{fffd}
 //~^ ERROR unknown start of token: \u{fffd}
-//~^^ ERROR can't use generic parameters from outer function [E0401]
+//~^^ ERROR can't use generic parameters from outer item [E0401]
 //~^^^ WARN type parameter `e` should have an upper camel case name
 
 fn main(){}

tests/ui/generics/issue-98432.rs

@@ -2,7 +2,7 @@ struct Struct<T>(T);
 
 impl<T> Struct<T> {
     const CONST: fn() = || {
-        struct _Obligation where T:; //~ ERROR can't use generic parameters from outer function
+        struct _Obligation where T:; //~ ERROR can't use generic parameters from outer item
     };
 }
 

tests/ui/generics/issue-98432.stderr

@@ -1,13 +1,13 @@
-error[E0401]: can't use generic parameters from outer function
+error[E0401]: can't use generic parameters from outer item
   --> $DIR/issue-98432.rs:5:34
    |
 LL | impl<T> Struct<T> {
-   |      - type parameter from outer function
+   |      - type parameter from outer item
 LL |     const CONST: fn() = || {
 LL |         struct _Obligation where T:;
-   |                           -      ^ use of generic parameter from outer function
+   |                           -      ^ use of generic parameter from outer item
    |                           |
-   |                           help: try using a local generic parameter instead: `<T>`
+   |                           help: try introducing a local generic parameter here: `<T>`
 
 error: aborting due to previous error