Auto merge of #104102 - Dylan-DPC:rollup-0eakshe, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #103757 (Mention const and lifetime parameters in error E0207)
 - #103986 (Don't silently eat label before block in block-like expr)
 - #104003 (Move some tests to more reasonable directories)
 - #104038 (Normalize types when deducing closure signature from supertraits)
 - #104052 (Fix `resolution_failure` ICE)
 - #104090 (Modify comment syntax error)

Failed merges:

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

4 files changed, 88 insertions, 13 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0207.md b/compiler/rustc_error_codes/src/error_codes/E0207.md
index 8a7923ac93f..95e7c9fc76c 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0207.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0207.md
@@ -1,4 +1,5 @@
-A type parameter that is specified for `impl` is not constrained.
+A type, const or lifetime parameter that is specified for `impl` is not
+constrained.
 
 Erroneous code example:
 
@@ -14,8 +15,8 @@ impl<T: Default> Foo {
 }
 ```
 
-Any type parameter of an `impl` must meet at least one of
-the following criteria:
+Any type or const parameter of an `impl` must meet at least one of the
+following criteria:
 
  - it appears in the _implementing type_ of the impl, e.g. `impl<T> Foo<T>`
  - for a trait impl, it appears in the _implemented trait_, e.g.
@@ -23,6 +24,9 @@ the following criteria:
  - it is bound as an associated type, e.g. `impl<T, U> SomeTrait for T
    where T: AnotherTrait<AssocType=U>`
 
+Any unconstrained lifetime parameter of an `impl` is not supported if the
+lifetime parameter is used by an associated type.
+
 ### Error example 1
 
 Suppose we have a struct `Foo` and we would like to define some methods for it.
@@ -32,7 +36,6 @@ The problem is that the parameter `T` does not appear in the implementing type
 (`Foo`) of the impl. In this case, we can fix the error by moving the type
 parameter from the `impl` to the method `get`:
 
-
 ```
 struct Foo;
 
@@ -128,6 +131,70 @@ impl<T: Default> Maker<Foo<T>> for FooMaker {
 }
 ```
 
+### Error example 3
+
+Suppose we have a struct `Foo` and we would like to define some methods for it.
+The following code example has a definition which leads to a compiler error:
+
+```compile_fail,E0207
+struct Foo;
+
+impl<const T: i32> Foo {
+    // error: the const parameter `T` is not constrained by the impl trait, self
+    // type, or predicates [E0207]
+    fn get(&self) -> i32 {
+        i32::default()
+    }
+}
+```
+
+The problem is that the const parameter `T` does not appear in the implementing
+type (`Foo`) of the impl. In this case, we can fix the error by moving the type
+parameter from the `impl` to the method `get`:
+
+
+```
+struct Foo;
+
+// Move the const parameter from the impl to the method
+impl Foo {
+    fn get<const T: i32>(&self) -> i32 {
+        i32::default()
+    }
+}
+```
+
+### Error example 4
+
+Suppose we have a struct `Foo` and a struct `Bar` that uses lifetime `'a`. We
+would like to implement trait `Contains` for `Foo`. The trait `Contains` have
+the associated type `B`. The following code example has a definition which
+leads to a compiler error:
+
+```compile_fail,E0207
+struct Foo;
+struct Bar<'a>;
+
+trait Contains {
+    type B;
+
+    fn get(&self) -> i32;
+}
+
+impl<'a> Contains for Foo {
+    type B = Bar<'a>;
+
+    // error: the lifetime parameter `'a` is not constrained by the impl trait,
+    // self type, or predicates [E0207]
+    fn get(&self) -> i32 {
+        i32::default()
+    }
+}
+```
+
+Please note that unconstrained lifetime parameters are not supported if they are
+being used by an associated type.
+
 ### Additional information
 
 For more information, please see [RFC 447].
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 09df50c76b7..3001e799476 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -10,6 +10,7 @@ use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::LateBoundRegionConversionTime;
 use rustc_infer::infer::{InferOk, InferResult};
+use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::visit::TypeVisitable;
 use rustc_middle::ty::{self, Ty};
@@ -22,7 +23,7 @@ use std::cmp;
 use std::iter;
 
 /// What signature do we *expect* the closure to have from context?
-#[derive(Debug)]
+#[derive(Debug, Clone, TypeFoldable, TypeVisitable)]
 struct ExpectedSig<'tcx> {
     /// Span that gave us this expectation, if we know that.
     cause_span: Option<Span>,
@@ -241,9 +242,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if expected_sig.is_none()
                 && let ty::PredicateKind::Projection(proj_predicate) = bound_predicate.skip_binder()
             {
-                expected_sig = self.deduce_sig_from_projection(
+                expected_sig = self.normalize_associated_types_in(
+                    obligation.cause.span,
+                    self.deduce_sig_from_projection(
                     Some(obligation.cause.span),
-                    bound_predicate.rebind(proj_predicate),
+                        bound_predicate.rebind(proj_predicate),
+                    ),
                 );
             }
 
diff --git a/compiler/rustc_macros/src/diagnostics/error.rs b/compiler/rustc_macros/src/diagnostics/error.rs
index 0b1ededa775..4612f54e4b1 100644
--- a/compiler/rustc_macros/src/diagnostics/error.rs
+++ b/compiler/rustc_macros/src/diagnostics/error.rs
@@ -84,7 +84,7 @@ pub(crate) fn invalid_attr(attr: &Attribute, meta: &Meta) -> Diagnostic {
     }
 }
 
-/// Emit a error diagnostic for an invalid attribute (optionally performing additional decoration
+/// Emit an error diagnostic for an invalid attribute (optionally performing additional decoration
 /// using the `FnOnce` passed in `diag`) and return `Err(ErrorHandled)`.
 ///
 /// For methods that return a `Result<_, DiagnosticDeriveError>`:
@@ -126,7 +126,7 @@ pub(crate) fn invalid_nested_attr(attr: &Attribute, nested: &NestedMeta) -> Diag
     }
 }
 
-/// Emit a error diagnostic for an invalid nested attribute (optionally performing additional
+/// Emit an error diagnostic for an invalid nested attribute (optionally performing additional
 /// decoration using the `FnOnce` passed in `diag`) and return `Err(ErrorHandled)`.
 ///
 /// For methods that return a `Result<_, DiagnosticDeriveError>`:
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 7dc4fd0044f..c609aa93da3 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -2468,11 +2468,15 @@ impl<'a> Parser<'a> {
     }
 
     pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
-        let Some(label) = self.eat_label().filter(|_| {
-            self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
-        }) else {
+        // Check for `'a : {`
+        if !(self.check_lifetime()
+            && self.look_ahead(1, |tok| tok.kind == token::Colon)
+            && self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Brace)))
+        {
             return false;
-        };
+        }
+        let label = self.eat_label().expect("just checked if a label exists");
+        self.bump(); // eat `:`
         let span = label.ident.span.to(self.prev_token.span);
         let mut err = self.struct_span_err(span, "block label not supported here");
         err.span_label(span, "not supported here");