Rollup merge of rust-lang#139200 - xizheyin:issue-139174, r=compiler-errors

Skip suggest impl or dyn when poly trait is not a real trait

Fixes rust-lang#139174
When `poly_trait_ref` is not a real trait, we should stop suggesting `impl` and `dyn` to avoid false positives. 3 cases were added to the ui test.
https://github.com/rust-lang/rust/blob/0b45675cfcec57f30a3794e1a1e18423aa9cf200/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs#L88-L93

In the first commit, I submitted the test and passed it. In the second commit, I modified the code and we can see the changes in the test.

r? compiler

Author: Zalathar

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -86,6 +86,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 "expected a type, found a trait"
             );
             if self_ty.span.can_be_used_for_suggestions()
+                && poly_trait_ref.trait_ref.trait_def_id().is_some()
                 && !self.maybe_suggest_impl_trait(self_ty, &mut diag)
                 && !self.maybe_suggest_dyn_trait(self_ty, sugg, &mut diag)
             {

tests/ui/traits/object/suggestion-trait-object-issue-139174.rs

@@ -0,0 +1,24 @@
+//@compile-flags: --edition 2021
+
+fn f<'a>(x: Box<dyn Fn() -> Option<usize + 'a>>) -> usize {
+    //~^ ERROR expected trait, found builtin type `usize`
+    //~| ERROR expected a type, found a trait [E0782]
+    0
+}
+
+fn create_adder<'a>(x: i32) -> usize + 'a {
+    //~^ ERROR expected trait, found builtin type `usize`
+    //~| ERROR expected a type, found a trait [E0782]
+    move |y| x + y
+}
+
+struct Struct<'a>{
+    x: usize + 'a,
+    //~^ ERROR expected trait, found builtin type `usize`
+    //~| ERROR expected a type, found a trait [E0782]
+}
+
+
+fn main() {
+
+}

tests/ui/traits/object/suggestion-trait-object-issue-139174.stderr

@@ -0,0 +1,40 @@
+error[E0404]: expected trait, found builtin type `usize`
+  --> $DIR/suggestion-trait-object-issue-139174.rs:3:36
+   |
+LL | fn f<'a>(x: Box<dyn Fn() -> Option<usize + 'a>>) -> usize {
+   |                                    ^^^^^ not a trait
+
+error[E0404]: expected trait, found builtin type `usize`
+  --> $DIR/suggestion-trait-object-issue-139174.rs:9:32
+   |
+LL | fn create_adder<'a>(x: i32) -> usize + 'a {
+   |                                ^^^^^ not a trait
+
+error[E0404]: expected trait, found builtin type `usize`
+  --> $DIR/suggestion-trait-object-issue-139174.rs:16:8
+   |
+LL |     x: usize + 'a,
+   |        ^^^^^ not a trait
+
+error[E0782]: expected a type, found a trait
+  --> $DIR/suggestion-trait-object-issue-139174.rs:3:36
+   |
+LL | fn f<'a>(x: Box<dyn Fn() -> Option<usize + 'a>>) -> usize {
+   |                                    ^^^^^^^^^^
+
+error[E0782]: expected a type, found a trait
+  --> $DIR/suggestion-trait-object-issue-139174.rs:9:32
+   |
+LL | fn create_adder<'a>(x: i32) -> usize + 'a {
+   |                                ^^^^^^^^^^
+
+error[E0782]: expected a type, found a trait
+  --> $DIR/suggestion-trait-object-issue-139174.rs:16:8
+   |
+LL |     x: usize + 'a,
+   |        ^^^^^^^^^^
+
+error: aborting due to 6 previous errors
+
+Some errors have detailed explanations: E0404, E0782.
+For more information about an error, try `rustc --explain E0404`.