aaron.ballman added inline comments.
================
Comment at: clang/lib/Parse/ParseExpr.cpp:1515
+ // This is a temporary fix while we don't support C2x 6.5.2.5p4
+ if (getLangOpts().C2x && GetLookAheadToken(2).getKind() == tok::l_brace) {
+ Diag(Tok, diag::err_c2x_auto_compound_literal_not_allowed);
----------------
to268 wrote:
> to268 wrote:
> > aaron.ballman wrote:
> > > Why would this not be handled from `Sema::ActOnCompoundLiteral()`?
> > You're right, it's better to handle this in `Sema::ActOnCompoundLiteral()`
> > The problem is that right now, the usage of the `auto` keyword in a
> > compound literal isn't parsed as a compound literal.
> > This compound literal is unable to reach `Sema::ActOnCompoundLiteral()`
> > because the parser emits that it's an invalid expression.
> >
> > To summarize, i'm unable to handle handle a compound literal that uses the
> > `auto` keyword inside `Sema::ActOnCompoundLiteral()`
> > if it's never going to be called.
> > ```
> > int test_ncl = (int){12}; // Parsed as a CL
> > auto test_cl = (auto){12}; // Not parsed as a CL and emits
> > "expected expression"
> > /*
> > * |-DeclStmt 0x562180ede8b0 <line:17:5, col:29>
> > * | `-VarDecl 0x562180ede730 <col:5, col:28> col:9 test_ncl 'int' cinit
> > * | `-ImplicitCastExpr 0x562180ede898 <col:20, col:28> 'int'
> > <LValueToRValue>
> > * | `-CompoundLiteralExpr 0x562180ede870 <col:20, col:28> 'int' lvalue
> > * | `-InitListExpr 0x562180ede828 <col:25, col:28> 'int'
> > * | `-IntegerLiteral 0x562180ede7b0 <col:26> 'int' 12
> > * |-DeclStmt 0x562180ede970 <line:18:5, col:30>
> > * | `-VarDecl 0x562180ede908 <col:5, col:10> col:10 invalid test_cl 'auto'
> > * `-ReturnStmt 0x562180ede9a8 <line:19:5, col:12>
> > * `-IntegerLiteral 0x562180ede988 <col:12> 'int' 0
> > */
> > ```
> When we are parsing an expression between parentheses in
> `Parser::ParseParenExpression()` line 2972,
> we are calling `Parser::isTypeIdInParens()` which when using C will return
> `true` if it's a type specifier,
> which is not the case for the `auto` keyword.
>
> Ultimately, we fall into the conditional block of
> `Parser::ParseParenExpression()` line 3191,
> which will return an `ExprError()` (AKA: a parsing error).
>
> This is why we are unable to forbid a compound literal using the `auto`
> keyword at the
> Semantic Analysis stage and why this feature is not working out of the box in
> the first place.
> When we are parsing an expression between parentheses in
> Parser::ParseParenExpression() line 2972,
we are calling Parser::isTypeIdInParens() which when using C will return true
if it's a type specifier,
which is not the case for the auto keyword.
Ahhhh, that makes a lot of sense!
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133289/new/
https://reviews.llvm.org/D133289
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