Auto merge of #117415 - matthiaskrgr:rollup-jr2p1t2, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #116862 (Detect when trait is implemented for type and suggest importing it)
 - #117389 (Some diagnostics improvements of `gen` blocks)
 - #117396 (Don't treat closures/coroutine types as part of the public API)
 - #117398 (Correctly handle nested or-patterns in exhaustiveness)
 - #117403 (Poison check_well_formed if method receivers are invalid to prevent typeck from running on it)
 - #117411 (Improve some diagnostics around `?Trait` bounds)
 - #117414 (Don't normalize to an un-revealed opaque when we hit the recursion limit)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_parse/messages.ftl

@@ -278,8 +278,8 @@ parse_found_expr_would_be_stmt = expected expression, found `{$token}`
 parse_function_body_equals_expr = function body cannot be `= expression;`
     .suggestion = surround the expression with `{"{"}` and `{"}"}` instead of `=` and `;`
 
-parse_gen_block = `gen` blocks are not yet implemented
-    .help = only the keyword is reserved for now
+parse_gen_fn = `gen` functions are not yet implemented
+    .help = for now you can use `gen {"{}"}` blocks and return `impl Iterator` instead
 
 parse_generic_args_in_pat_require_turbofish_syntax = generic args in patterns require the turbofish syntax
 

compiler/rustc_parse/src/errors.rs

@@ -521,9 +521,9 @@ pub(crate) struct CatchAfterTry {
 }
 
 #[derive(Diagnostic)]
-#[diag(parse_gen_block)]
+#[diag(parse_gen_fn)]
 #[help]
-pub(crate) struct GenBlock {
+pub(crate) struct GenFn {
     #[primary_span]
     pub span: Span,
 }

compiler/rustc_parse/src/parser/item.rs

@@ -2372,7 +2372,7 @@ impl<'a> Parser<'a> {
         }
 
         if let Gen::Yes { span, .. } = genness {
-            self.sess.emit_err(errors::GenBlock { span });
+            self.sess.emit_err(errors::GenFn { span });
         }
 
         if !self.eat_keyword_case(kw::Fn, case) {