Rollup merge of rust-lang#148370 - estebank:outer-param, r=JonathanBrouwer

Point at inner item when it uses generic type param from outer item or `Self`

Partially address rust-lang#37892.

In E0401 generated in resolve:
```
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 item
LL |     fn bfnr<U, V: Baz<U>, W: Fn()>(y: T) {
   |        ----                           ^ use of generic parameter from outer item
   |        |
   |        generic parameter used in this inner function
   |
help: try introducing a local generic parameter here
   |
LL |     fn bfnr<T, U, V: Baz<U>, W: Fn()>(y: T) {
   |             ++
```
In E0401 generated in hir_typeck:
```
error[E0401]: can't reference `Self` constructor from outer item
  --> $DIR/do-not-ice-on-note_and_explain.rs:6:13
   |
LL | impl<B> A<B> {
   | ------------ the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
LL |     fn d() {
LL |         fn d() {
   |            - `Self` used in this inner item
LL |             Self(1)
   |             ^^^^ help: replace `Self` with the actual type: `A`
```

Author: Zalathar

compiler/rustc_hir_typeck/messages.ftl

@@ -266,6 +266,8 @@ hir_typeck_self_ctor_from_outer_item = can't reference `Self` constructor from o
     .label = the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
     .suggestion = replace `Self` with the actual type
 
+hir_typeck_self_ctor_from_outer_item_inner_item = `Self` used in this inner item
+
 hir_typeck_slicing_suggestion = consider slicing here
 
 hir_typeck_struct_expr_non_exhaustive =

compiler/rustc_hir_typeck/src/errors.rs

@@ -978,6 +978,15 @@ pub(crate) struct SelfCtorFromOuterItem {
     pub impl_span: Span,
     #[subdiagnostic]
     pub sugg: Option<ReplaceWithName>,
+    #[subdiagnostic]
+    pub item: Option<InnerItem>,
+}
+
+#[derive(Subdiagnostic)]
+#[label(hir_typeck_self_ctor_from_outer_item_inner_item)]
+pub(crate) struct InnerItem {
+    #[primary_span]
+    pub span: Span,
 }
 
 #[derive(LintDiagnostic)]
@@ -987,6 +996,8 @@ pub(crate) struct SelfCtorFromOuterItemLint {
     pub impl_span: Span,
     #[subdiagnostic]
     pub sugg: Option<ReplaceWithName>,
+    #[subdiagnostic]
+    pub item: Option<InnerItem>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -1094,11 +1094,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     span: path_span,
                     name: self.tcx.item_name(def.did()).to_ident_string(),
                 });
+                let item = match self
+                    .tcx
+                    .hir_node_by_def_id(self.tcx.hir_get_parent_item(hir_id).def_id)
+                {
+                    hir::Node::Item(item) => Some(errors::InnerItem {
+                        span: item.kind.ident().map(|i| i.span).unwrap_or(item.span),
+                    }),
+                    _ => None,
+                };
                 if ty.raw.has_param() {
                     let guar = self.dcx().emit_err(errors::SelfCtorFromOuterItem {
                         span: path_span,
                         impl_span: tcx.def_span(impl_def_id),
                         sugg,
+                        item,
                     });
                     return (Ty::new_error(self.tcx, guar), res);
                 } else {
@@ -1109,6 +1119,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         errors::SelfCtorFromOuterItemLint {
                             impl_span: tcx.def_span(impl_def_id),
                             sugg,
+                            item,
                         },
                     );
                 }

compiler/rustc_resolve/messages.ftl

@@ -180,6 +180,11 @@ resolve_generic_params_from_outer_item_const = a `const` is a separate item from
 
 resolve_generic_params_from_outer_item_const_param = const parameter from outer item
 
+resolve_generic_params_from_outer_item_inner_item = {$is_self ->
+        [true] `Self`
+        *[false] generic parameter
+    } used in this inner {$descr}
+
 resolve_generic_params_from_outer_item_self_ty_alias = `Self` type implicitly declared here, by this `impl`
 
 resolve_generic_params_from_outer_item_self_ty_param = can't use `Self` here

compiler/rustc_resolve/src/diagnostics.rs

@@ -40,7 +40,7 @@ use crate::errors::{
     MaybeMissingMacroRulesName,
 };
 use crate::imports::{Import, ImportKind};
-use crate::late::{PatternSource, Rib};
+use crate::late::{DiagMetadata, PatternSource, Rib};
 use crate::{
     AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingError, BindingKey, Finalize,
     ForwardGenericParamBanReason, HasGenericParams, LexicalScopeBinding, MacroRulesScope, Module,
@@ -553,11 +553,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         resolution_error: ResolutionError<'ra>,
     ) -> Diag<'_> {
         match resolution_error {
-            ResolutionError::GenericParamsFromOuterItem(
+            ResolutionError::GenericParamsFromOuterItem {
                 outer_res,
                 has_generic_params,
                 def_kind,
-            ) => {
+                inner_item,
+            } => {
                 use errs::GenericParamsFromOuterItemLabel as Label;
                 let static_or_const = match def_kind {
                     DefKind::Static { .. } => {
@@ -575,6 +576,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     sugg: None,
                     static_or_const,
                     is_self,
+                    item: inner_item.as_ref().map(|(span, kind)| {
+                        errs::GenericParamsFromOuterItemInnerItem {
+                            span: *span,
+                            descr: kind.descr().to_string(),
+                        }
+                    }),
                 };
 
                 let sm = self.tcx.sess.source_map();
@@ -608,7 +615,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                 };
 
-                if let HasGenericParams::Yes(span) = has_generic_params {
+                if let HasGenericParams::Yes(span) = has_generic_params
+                    && !matches!(inner_item, Some((_, ItemKind::Delegation(..))))
+                {
                     let name = self.tcx.item_name(def_id);
                     let (span, snippet) = if span.is_empty() {
                         let snippet = format!("<{name}>");
@@ -2401,6 +2410,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         module: Option<ModuleOrUniformRoot<'ra>>,
         failed_segment_idx: usize,
         ident: Ident,
+        diag_metadata: Option<&DiagMetadata<'_>>,
     ) -> (String, Option<Suggestion>) {
         let is_last = failed_segment_idx == path.len() - 1;
         let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
@@ -2506,6 +2516,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         None,
                         &ribs[ns_to_try],
                         ignore_binding,
+                        diag_metadata,
                     ) {
                         // we found a locally-imported or available item/module
                         Some(LexicalScopeBinding::Item(binding)) => Some(binding),
@@ -2556,6 +2567,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     None,
                     &ribs[ValueNS],
                     ignore_binding,
+                    diag_metadata,
                 )
             } else {
                 None

compiler/rustc_resolve/src/errors.rs

@@ -24,6 +24,16 @@ pub(crate) struct GenericParamsFromOuterItem {
     #[subdiagnostic]
     pub(crate) static_or_const: Option<GenericParamsFromOuterItemStaticOrConst>,
     pub(crate) is_self: bool,
+    #[subdiagnostic]
+    pub(crate) item: Option<GenericParamsFromOuterItemInnerItem>,
+}
+
+#[derive(Subdiagnostic)]
+#[label(resolve_generic_params_from_outer_item_inner_item)]
+pub(crate) struct GenericParamsFromOuterItemInnerItem {
+    #[primary_span]
+    pub(crate) span: Span,
+    pub(crate) descr: String,
 }
 
 #[derive(Subdiagnostic)]
@@ -47,7 +57,12 @@ pub(crate) enum GenericParamsFromOuterItemLabel {
 }
 
 #[derive(Subdiagnostic)]
-#[suggestion(resolve_suggestion, code = "{snippet}", applicability = "maybe-incorrect")]
+#[suggestion(
+    resolve_suggestion,
+    code = "{snippet}",
+    applicability = "maybe-incorrect",
+    style = "verbose"
+)]
 pub(crate) struct GenericParamsFromOuterItemSugg {
     #[primary_span]
     pub(crate) span: Span,

compiler/rustc_resolve/src/ident.rs

@@ -12,7 +12,9 @@ use tracing::{debug, instrument};
 
 use crate::errors::{ParamKindInEnumDiscriminant, ParamKindInNonTrivialAnonConst};
 use crate::imports::{Import, NameResolution};
-use crate::late::{ConstantHasGenerics, NoConstantGenericsReason, PathSource, Rib, RibKind};
+use crate::late::{
+    ConstantHasGenerics, DiagMetadata, NoConstantGenericsReason, PathSource, Rib, RibKind,
+};
 use crate::macros::{MacroRulesScope, sub_namespace_match};
 use crate::{
     AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingKey, CmResolver, Determinacy,
@@ -295,6 +297,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         finalize: Option<Finalize>,
         ribs: &[Rib<'ra>],
         ignore_binding: Option<NameBinding<'ra>>,
+        diag_metadata: Option<&DiagMetadata<'_>>,
     ) -> Option<LexicalScopeBinding<'ra>> {
         assert!(ns == TypeNS || ns == ValueNS);
         let orig_ident = ident;
@@ -326,6 +329,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     finalize.map(|finalize| finalize.path_span),
                     *original_rib_ident_def,
                     ribs,
+                    diag_metadata,
                 )));
             } else if let RibKind::Block(Some(module)) = rib.kind
                 && let Ok(binding) = self.cm().resolve_ident_in_module_unadjusted(
@@ -1193,6 +1197,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         finalize: Option<Span>,
         original_rib_ident_def: Ident,
         all_ribs: &[Rib<'ra>],
+        diag_metadata: Option<&DiagMetadata<'_>>,
     ) -> Res {
         debug!("validate_res_from_ribs({:?})", res);
         let ribs = &all_ribs[rib_index + 1..];
@@ -1391,13 +1396,26 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     };
 
                     if let Some(span) = finalize {
+                        let item = if let Some(diag_metadata) = diag_metadata
+                            && let Some(current_item) = diag_metadata.current_item
+                        {
+                            let span = current_item
+                                .kind
+                                .ident()
+                                .map(|i| i.span)
+                                .unwrap_or(current_item.span);
+                            Some((span, current_item.kind.clone()))
+                        } else {
+                            None
+                        };
                         self.report_error(
                             span,
-                            ResolutionError::GenericParamsFromOuterItem(
-                                res,
+                            ResolutionError::GenericParamsFromOuterItem {
+                                outer_res: res,
                                 has_generic_params,
                                 def_kind,
-                            ),
+                                inner_item: item,
+                            },
                         );
                     }
                     return Res::Err;
@@ -1466,13 +1484,26 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
                     // This was an attempt to use a const parameter outside its scope.
                     if let Some(span) = finalize {
+                        let item = if let Some(diag_metadata) = diag_metadata
+                            && let Some(current_item) = diag_metadata.current_item
+                        {
+                            let span = current_item
+                                .kind
+                                .ident()
+                                .map(|i| i.span)
+                                .unwrap_or(current_item.span);
+                            Some((span, current_item.kind.clone()))
+                        } else {
+                            None
+                        };
                         self.report_error(
                             span,
-                            ResolutionError::GenericParamsFromOuterItem(
-                                res,
+                            ResolutionError::GenericParamsFromOuterItem {
+                                outer_res: res,
                                 has_generic_params,
                                 def_kind,
-                            ),
+                                inner_item: item,
+                            },
                         );
                     }
                     return Res::Err;
@@ -1501,6 +1532,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             None,
             None,
             ignore_import,
+            None,
         )
     }
     #[instrument(level = "debug", skip(self))]
@@ -1522,6 +1554,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             None,
             ignore_binding,
             ignore_import,
+            None,
         )
     }
 
@@ -1535,6 +1568,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         ribs: Option<&PerNS<Vec<Rib<'ra>>>>,
         ignore_binding: Option<NameBinding<'ra>>,
         ignore_import: Option<Import<'ra>>,
+        diag_metadata: Option<&DiagMetadata<'_>>,
     ) -> PathResult<'ra> {
         let mut module = None;
         let mut module_had_parse_errors = false;
@@ -1675,6 +1709,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     finalize,
                     &ribs[ns],
                     ignore_binding,
+                    diag_metadata,
                 ) {
                     // we found a locally-imported or available item/module
                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
@@ -1800,6 +1835,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                                 module,
                                 segment_idx,
                                 ident,
+                                diag_metadata,
                             )
                         },
                     );

compiler/rustc_resolve/src/late.rs

@@ -670,7 +670,7 @@ pub(crate) struct UnnecessaryQualification<'ra> {
 }
 
 #[derive(Default, Debug)]
-struct DiagMetadata<'ast> {
+pub(crate) struct DiagMetadata<'ast> {
     /// The current trait's associated items' ident, used for diagnostic suggestions.
     current_trait_assoc_items: Option<&'ast [Box<AssocItem>]>,
 
@@ -680,8 +680,8 @@ struct DiagMetadata<'ast> {
     /// The current self item if inside an ADT (used for better errors).
     current_self_item: Option<NodeId>,
 
-    /// The current trait (used to suggest).
-    current_item: Option<&'ast Item>,
+    /// The current item being evaluated (used for suggestions and more detail in errors).
+    pub(crate) current_item: Option<&'ast Item>,
 
     /// When processing generic arguments and encountering an unresolved ident not found,
     /// suggest introducing a type or const param depending on the context.
@@ -1460,6 +1460,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             None,
             &self.ribs[ns],
             None,
+            Some(&self.diag_metadata),
         )
     }
 
@@ -1477,6 +1478,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             finalize,
             &self.ribs[ns],
             ignore_binding,
+            Some(&self.diag_metadata),
         )
     }
 
@@ -1496,6 +1498,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             Some(&self.ribs),
             None,
             None,
+            Some(&self.diag_metadata),
         )
     }
 

compiler/rustc_resolve/src/lib.rs

@@ -241,7 +241,12 @@ struct BindingError {
 #[derive(Debug)]
 enum ResolutionError<'ra> {
     /// Error E0401: can't use type or const parameters from outer item.
-    GenericParamsFromOuterItem(Res, HasGenericParams, DefKind),
+    GenericParamsFromOuterItem {
+        outer_res: Res,
+        has_generic_params: HasGenericParams,
+        def_kind: DefKind,
+        inner_item: Option<(Span, ast::ItemKind)>,
+    },
     /// Error E0403: the name is already used for a type or const parameter in this generic
     /// parameter list.
     NameAlreadyUsedInParameterList(Ident, Span),

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

@@ -4,9 +4,14 @@ error[E0401]: can't use generic parameters from outer item
 LL | fn foo<const X: u32>() {
    |              - const parameter from outer item
 LL |     fn bar() -> u32 {
-   |           - help: try introducing a local generic parameter here: `<X>`
+   |        --- generic parameter used in this inner function
 LL |         X
    |         ^ use of generic parameter from outer item
+   |
+help: try introducing a local generic parameter here
+   |
+LL |     fn bar<X>() -> u32 {
+   |           +++
 
 error: aborting due to 1 previous error