[PATCH] D99517: Implemented [[clang::musttail]] attribute for guaranteed tail calls.

[Josh Haberman via Phabricator via cfe-commits]

haberman added inline comments.


================
Comment at: clang/lib/Sema/SemaStmt.cpp:711
+    if (CalleeQualType.isNull()) {
+      // The function callee is invalid and already triggered an error.
+      // Avoid compounding errors.
----------------
rsmith wrote:
> Even in invalid code we should never see a `CallExpr` whose callee has a null type; if `Sema` can't form an `Expr` that meets the normal expression invariants during error recovery, it doesn't build one at all. I think you can remove this `if`.
Without this if(), I crash on this test case. What do you think?

```
struct TestBadPMF {
  int (TestBadPMF::*pmf)();
  void BadPMF() {
    [[clang::musttail]] return ((*this)->*pmf)(); // expected-error {{left hand operand to ->* must be a pointer to class compatible with the right hand operand, but is 'TestBadPMF'}}
  }
};
```

Dump of `CalleeExpr` is:

```
RecoveryExpr 0x106671e8 '<dependent type>' contains-errors lvalue
|-ParenExpr 0x10667020 'struct TestBadPMF' lvalue
| `-UnaryOperator 0x10667008 'struct TestBadPMF' lvalue prefix '*' cannot overflow
|   `-CXXThisExpr 0x10666ff8 'struct TestBadPMF *' this
`-MemberExpr 0x10667050 'int (struct TestBadPMF::*)(void)' lvalue ->pmf 0x10666ed0
  `-CXXThisExpr 0x10667040 'struct TestBadPMF *' implicit this
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D99517/new/

https://reviews.llvm.org/D99517