Suggest 'static when in static/const items.

Author: cjgillot

compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs

@@ -317,6 +317,30 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
                     let hir::ParamName::Plain(name) = p.name else { return None };
                     Some(name.to_string())
                 }));
+                // Suggest `'static` when in const/static item-like.
+                if let hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Static { .. } | hir::ItemKind::Const { .. },
+                    ..
+                })
+                | hir::Node::TraitItem(hir::TraitItem {
+                    kind: hir::TraitItemKind::Const { .. },
+                    ..
+                })
+                | hir::Node::ImplItem(hir::ImplItem {
+                    kind: hir::ImplItemKind::Const { .. },
+                    ..
+                })
+                | hir::Node::ForeignItem(hir::ForeignItem {
+                    kind: hir::ForeignItemKind::Static { .. },
+                    ..
+                })
+                | hir::Node::AnonConst(..) = node
+                {
+                    ret.extend(
+                        std::iter::repeat("'static".to_owned())
+                            .take(num_params_to_take.saturating_sub(ret.len())),
+                    );
+                }
                 if ret.len() >= num_params_to_take {
                     return ret[..num_params_to_take].join(", ");
                 }

src/test/ui/generic-associated-types/elided-in-expr-position.stderr

@@ -11,7 +11,7 @@ LL |     type Assoc<'a> where Self: 'a;
    |          ^^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn g(&self) -> Self::Assoc<'_>;
+LL |     fn g(&self) -> Self::Assoc<'a>;
    |                          ~~~~~~~~~
 
 error[E0107]: missing generics for associated type `Trait::Assoc`
@@ -27,7 +27,7 @@ LL |     type Assoc<'a> where Self: 'a;
    |          ^^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn g(&self) -> Self::Assoc<'_> {
+LL |     fn g(&self) -> Self::Assoc<'a> {
    |                          ~~~~~~~~~
 
 error: aborting due to 2 previous errors

src/test/ui/generic-associated-types/issue-81862.stderr

@@ -11,7 +11,7 @@ LL |     type Item<'a>;
    |          ^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn next(&mut self) -> Option<Self::Item<'_>>;
+LL |     fn next(&mut self) -> Option<Self::Item<'a>>;
    |                                        ~~~~~~~~
 
 error: aborting due to previous error

src/test/ui/suggestions/missing-lifetime-specifier.stderr

@@ -171,8 +171,8 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                       ++++
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       +++++++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:43:44
@@ -243,8 +243,8 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                       ++++
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       +++++++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:51:45
@@ -261,8 +261,8 @@ LL | trait Tar<'t, 'k, I> {}
    |       ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                        ++++
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        +++++++++
 
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-specifier.rs:51:44
@@ -360,8 +360,8 @@ LL | trait Tar<'t, 'k, I> {}
    |       ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                        ++++
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        +++++++++
 
 error: aborting due to 24 previous errors