Handle macro invocation in attribute during parse

```
error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found macro `concat`
  --> $DIR/macro-in-attribute.rs:4:21
   |
LL | #[deprecated(note = concat!("a", "b"))]
   |                     ^^^^^^^^^^^^^^^^^ macros are not allowed here
```

Author: estebank

compiler/rustc_attr_parsing/messages.ftl

@@ -192,6 +192,7 @@ attr_parsing_invalid_attr_unsafe = `{$name}` is not an unsafe attribute
 attr_parsing_invalid_meta_item = expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found {$descr}
     .remove_neg_sugg = negative numbers are not literals, try removing the `-` sign
     .quote_ident_sugg = surround the identifier with quotation marks to make it into a string literal
+    .label = macros are not allowed here
 
 attr_parsing_suffixed_literal_in_attribute = suffixed literals are not allowed in attributes
     .help = instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), use an unsuffixed version (`1`, `1.0`, etc.)

compiler/rustc_attr_parsing/src/parser.rs

@@ -13,7 +13,7 @@ use rustc_ast_pretty::pprust;
 use rustc_errors::{Diag, PResult};
 use rustc_hir::{self as hir, AttrPath};
 use rustc_parse::exp;
-use rustc_parse::parser::{Parser, PathStyle, token_descr};
+use rustc_parse::parser::{ForceCollect, Parser, PathStyle, token_descr};
 use rustc_session::errors::{create_lit_error, report_lit_error};
 use rustc_session::parse::ParseSess;
 use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, sym};
@@ -476,6 +476,7 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
             descr: token_descr(&self.parser.token),
             quote_ident_sugg: None,
             remove_neg_sugg: None,
+            macro_call: None,
         };
 
         // Suggest quoting idents, e.g. in `#[cfg(key = value)]`. We don't use `Token::ident` and
@@ -484,20 +485,37 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
         if self.parser.prev_token == token::Eq
             && let token::Ident(..) = self.parser.token.kind
         {
-            let before = self.parser.token.span.shrink_to_lo();
-            while let token::Ident(..) = self.parser.token.kind {
-                self.parser.bump();
+            if self.parser.look_ahead(1, |t| matches!(t.kind, token::TokenKind::Bang)) {
+                let snapshot = self.parser.create_snapshot_for_diagnostic();
+                let stmt = self.parser.parse_stmt_without_recovery(false, ForceCollect::No, false);
+                match stmt {
+                    Ok(Some(stmt)) => {
+                        // The user tried to write something like
+                        // `#[deprecated(note = concat!("a", "b"))]`.
+                        err.descr = format!("macro {}", err.descr);
+                        err.macro_call = Some(stmt.span);
+                        err.span = stmt.span;
+                    }
+                    Ok(None) => {}
+                    Err(err) => {
+                        err.cancel();
+                        self.parser.restore_snapshot(snapshot);
+                    }
+                }
+            } else {
+                let before = self.parser.token.span.shrink_to_lo();
+                while let token::Ident(..) = self.parser.token.kind {
+                    self.parser.bump();
+                }
+                err.quote_ident_sugg = Some(InvalidMetaItemQuoteIdentSugg {
+                    before,
+                    after: self.parser.prev_token.span.shrink_to_hi(),
+                });
             }
-            err.quote_ident_sugg = Some(InvalidMetaItemQuoteIdentSugg {
-                before,
-                after: self.parser.prev_token.span.shrink_to_hi(),
-            });
         }
 
         if self.parser.token == token::Minus
-            && self
-                .parser
-                .look_ahead(1, |t| matches!(t.kind, rustc_ast::token::TokenKind::Literal { .. }))
+            && self.parser.look_ahead(1, |t| matches!(t.kind, token::TokenKind::Literal { .. }))
         {
             err.remove_neg_sugg =
                 Some(InvalidMetaItemRemoveNegSugg { negative_sign: self.parser.token.span });

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -801,6 +801,8 @@ pub(crate) struct InvalidMetaItem {
     pub quote_ident_sugg: Option<InvalidMetaItemQuoteIdentSugg>,
     #[subdiagnostic]
     pub remove_neg_sugg: Option<InvalidMetaItemRemoveNegSugg>,
+    #[label]
+    pub macro_call: Option<Span>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -278,7 +278,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Replace `self` with `snapshot.parser`.
-    pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
+    pub fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
         *self = snapshot.parser;
     }
 

tests/ui/parser/macro/macro-in-attribute.rs

@@ -0,0 +1,9 @@
+// Test for #146325.
+// Ensure that when we encounter a macro invocation in an attribute, we don't suggest nonsense.
+
+#[deprecated(note = concat!("a", "b"))]
+struct X;
+//~^^ ERROR: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found macro `concat`
+//~| NOTE: macros are not allowed here
+
+fn main() {}

tests/ui/parser/macro/macro-in-attribute.stderr

@@ -0,0 +1,8 @@
+error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found macro `concat`
+  --> $DIR/macro-in-attribute.rs:4:21
+   |
+LL | #[deprecated(note = concat!("a", "b"))]
+   |                     ^^^^^^^^^^^^^^^^^ macros are not allowed here
+
+error: aborting due to 1 previous error
+