hokein added a comment.
Thanks for looking at this. It seems an issue caused by
https://reviews.llvm.org/D120812 (sorry), where we build a recovery-expr to
model declrefexpr pointing to an invalid decl.
================
Comment at: clang/lib/Sema/TreeTransform.h:14709
// -> is never a builtin operation.
+ if (First->getType()->isDependentType())
+ return ExprError();
----------------
It looks like we are somehow doing a transformation on a dependent-type
expression (I think it is the recoveryExpression) during the template
instantiation, which leads to the crash.
================
Comment at: clang/test/SemaCXX/arrow-operator.cpp:79
+void foo() {
+ // x is dependent.
+ A<int>& x = blah[7]; // expected-error {{use of undeclared identifier
'blah'}} \
----------------
The AST nodes looks weird and inconsistent in the primary template and
instantiated template.
VarDecl `x` AST node in the primary template look like (with a Valid bit!)
```
`-DeclStmt
`-VarDecl x 'A<int> &'
```
while in the instantiated template (with an **Invalid** bit!):
```
`-DeclStmt
`-VarDecl invalid x 'A<int> &'
```
The difference of valid bit results in two different forms of the expression
`x->call()` (a normal CXXMemberCallExpr vs. a dependent-type CallExpr wrapping
a RecoveryExpr), I think this is likely the root cause of the crash.
If we invalidate the VarDecl x in the primary template for this case, the issue
should be gone. This seems a reasonable fix to me -- a reference-type VarDecl
is invalid, when it doesn't have an initializer (either 1. it is not written in
the source code or 2. it is too malformed to preserve ). Clang AST already
does 1. We're missing 2, I think it is in `Sema::ActOnInitializerError`.
================
Comment at: clang/test/SemaCXX/arrow-operator.cpp:81
+ A<int>& x = blah[7]; // expected-error {{use of undeclared identifier
'blah'}} \
+ // expected-error {{declaration of reference variable
'x' requires an initializer}}
+ x->call();
----------------
if we mark vardecl x invalid, I think the bogus `requires an initializer`
diagnostic will be gone.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D121824/new/
https://reviews.llvm.org/D121824
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