Auto merge of #55451 - estebank:arg-doc, r=pnkfelix

Custom diagnostic when trying to doc comment argument

When writing

```
pub fn f(
    /// Comment
    id: u8,
) {}
```

Produce a targeted diagnostic

```
error: documentation comments cannot be applied to method arguments
  --> $DIR/fn-arg-doc-comment.rs:2:5
   |
LL |     /// Comment
   |     ^^^^^^^^^^^ doc comments are not allowed here
```

Fix #54801.

3 files changed, 3 insertions, 3 deletions

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index a148a649665..cc8af70a050 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -1032,7 +1032,7 @@ impl<'a> Parser<'a> {
                 }
             },
             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
-            AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat()?),
+            AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat(None)?),
         })
     }
 
diff --git a/src/libsyntax/ext/quote.rs b/src/libsyntax/ext/quote.rs
index 62bc9fae3b5..37800a334c6 100644
--- a/src/libsyntax/ext/quote.rs
+++ b/src/libsyntax/ext/quote.rs
@@ -419,7 +419,7 @@ pub fn parse_item_panic(parser: &mut Parser) -> Option<P<Item>> {
 }
 
 pub fn parse_pat_panic(parser: &mut Parser) -> P<Pat> {
-    panictry!(parser.parse_pat())
+    panictry!(parser.parse_pat(None))
 }
 
 pub fn parse_arm_panic(parser: &mut Parser) -> Arm {
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 38bbfc6b4c3..06c1d58070e 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -888,7 +888,7 @@ fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
                 FatalError.raise();
             }
         },
-        "pat" => token::NtPat(panictry!(p.parse_pat())),
+        "pat" => token::NtPat(panictry!(p.parse_pat(None))),
         "expr" => token::NtExpr(panictry!(p.parse_expr())),
         "literal" => token::NtLiteral(panictry!(p.parse_literal_maybe_minus())),
         "ty" => token::NtTy(panictry!(p.parse_ty())),