[PATCH] D149276: [Clang] Fix parsing of `(auto(x))`.

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/docs/ReleaseNotes.rst:360
   (`#61336 <https://github.com/llvm/llvm-project/issues/61336>`_)
+- Fix parsing of `auto(x)`, when it is surrounded by parenthesese.
 
----------------



================
Comment at: clang/include/clang/Parse/Parser.h:2655
   TPResult TryParseOperatorId();
-  TPResult TryParseInitDeclaratorList();
+  TPResult TryParseInitDeclaratorList(bool mayHaveTrailingReturnType = false);
   TPResult TryParseDeclarator(bool mayBeAbstract, bool mayHaveIdentifier = true,
----------------



================
Comment at: clang/include/clang/Parse/Parser.h:2663
           ImplicitTypenameContext::No);
-  TPResult TryParseFunctionDeclarator();
+  TPResult TryParseFunctionDeclarator(bool mayHaveTrailingReturnType = false);
   TPResult TryParseBracketDeclarator();
----------------



================
Comment at: clang/lib/Parse/ParseTentative.cpp:237
       ConsumeAnnotationToken();
-    if (Tok.is(tok::identifier))
+    if (Tok.isOneOf(tok::identifier, tok::kw_auto))
       ConsumeToken();
----------------
This smells a bit off to me because of the comments above -- this is trying to parse an elaborated type specifier, and `auto` cannot appear in this position for that case. Can you help me understand what's going on?


================
Comment at: clang/lib/Parse/ParseTentative.cpp:323
+Parser::TPResult
+Parser::TryParseInitDeclaratorList(bool mayHaveTrailingReturnType) {
   while (true) {
----------------



================
Comment at: clang/lib/Parse/ParseTentative.cpp:545
   // FIXME: A tag definition unambiguously tells us this is an init-statement.
+  bool mayHaveTrailingReturnType = Tok.is(tok::kw_auto);
   if (State.update(TryConsumeDeclarationSpecifier()))
----------------



================
Comment at: clang/lib/Parse/ParseTentative.cpp:1416-1417
+  case tok::kw_auto: {
+    if (NextToken().is(tok::l_brace))
+      return TPResult::False;
+    if (NextToken().is(tok::l_paren)) {
----------------
This seems incorrect to me, consider:
```
auto [[clang::annotate_type("test")]] i = 12;
```
https://godbolt.org/z/7Gx3Gb18h


================
Comment at: clang/lib/Parse/ParseTentative.cpp:1418-1420
+    if (NextToken().is(tok::l_paren)) {
+      return TPResult::Ambiguous;
+    }
----------------



================
Comment at: clang/lib/Parse/ParseTentative.cpp:2114
+Parser::TPResult
+Parser::TryParseFunctionDeclarator(bool mayHaveTrailingReturnType) {
   // The '(' is already parsed.
----------------



================
Comment at: clang/test/Parser/cxx1z-decomposition.cpp:97
     decltype(auto) [b] = s; // expected-error {{cannot be declared with type 'decltype(auto)'}}
-    auto ([c]) = s; // expected-error {{cannot be declared with parentheses}}
+    auto ([c]) = s; // expected-error {{'auto' not allowed here}} \
+                    // expected-error {{use of undeclared identifier 'c'}} \
----------------
This first diagnostic is incorrect -- `auto` is definitely allowed there, just that the rest of the declaration is nonsense. I think the "use of undeclared identifier" diagnostic is reasonable. The lambda diagnostic is.... interesting.

Any way you can improve this, or is that a slog?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D149276/new/

https://reviews.llvm.org/D149276