Emits error if has bound regions

Author: mu001999

compiler/rustc_hir_analysis/src/check/entry.rs

@@ -1,7 +1,7 @@
 use rustc_hir as hir;
 use rustc_hir::Node;
 use rustc_infer::infer::TyCtxtInferExt;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::config::EntryFnType;
 use rustc_span::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_span::{symbol::sym, Span};
@@ -124,6 +124,10 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
     if let Some(term_did) = tcx.lang_items().termination() {
         let return_ty = main_fnsig.output();
         let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);
+        if return_ty.has_bound_regions() {
+            tcx.sess.emit_err(errors::MainFunctionReturnTypeGeneric { span: return_ty_span });
+            return;
+        }
         let return_ty = return_ty.skip_binder();
         let infcx = tcx.infer_ctxt().build();
         let cause = traits::ObligationCause::new(

tests/ui/entry-point/issue-119209.rs

@@ -0,0 +1,4 @@
+type Foo<'a, 'b> = (i32, impl PartialEq); //~ ERROR `impl Trait` in type aliases is unstable
+fn main<'a, 'main>(i: &'a i32) -> Foo<'a, 'b> {}  //~ ERROR use of undeclared lifetime name `'b`
+//~^ ERROR mismatched types
+//~^^ ERROR `main` function return type is not allowed to have generic parameters

tests/ui/entry-point/issue-119209.stderr

@@ -0,0 +1,38 @@
+error[E0261]: use of undeclared lifetime name `'b`
+  --> $DIR/issue-119209.rs:2:43
+   |
+LL | fn main<'a, 'main>(i: &'a i32) -> Foo<'a, 'b> {}
+   |         -                                 ^^ undeclared lifetime
+   |         |
+   |         help: consider introducing lifetime `'b` here: `'b,`
+
+error[E0658]: `impl Trait` in type aliases is unstable
+  --> $DIR/issue-119209.rs:1:26
+   |
+LL | type Foo<'a, 'b> = (i32, impl PartialEq);
+   |                          ^^^^^^^^^^^^^^
+   |
+   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
+
+error[E0308]: mismatched types
+  --> $DIR/issue-119209.rs:2:35
+   |
+LL | fn main<'a, 'main>(i: &'a i32) -> Foo<'a, 'b> {}
+   |    ----                           ^^^^^^^^^^^ expected `(i32, _)`, found `()`
+   |    |
+   |    implicitly returns `()` as its body has no tail or `return` expression
+   |
+   = note:  expected tuple `(i32, _)`
+           found unit type `()`
+
+error[E0131]: `main` function return type is not allowed to have generic parameters
+  --> $DIR/issue-119209.rs:2:35
+   |
+LL | fn main<'a, 'main>(i: &'a i32) -> Foo<'a, 'b> {}
+   |                                   ^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0131, E0261, E0308, E0658.
+For more information about an error, try `rustc --explain E0131`.