[Sema] Check nullness of captured type before use

[ecnelises]

No description provided.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Qiu Chaofan (ecnelises)

Changes

Fixes #72198

---

Full diff: https://github.com/llvm/llvm-project/pull/72230.diff

2 Files Affected:

• (modified) clang/lib/Sema/SemaExpr.cpp (+2)
• (modified) clang/test/SemaCXX/lambda-invalid-capture.cpp (+6)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 5b0c4439fd1710c..cb7383ea8790f67 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -19773,6 +19773,8 @@ bool Sema::tryCaptureVariable(
   // declcontext can either capture the variable or have already captured
   // the variable.
   CaptureType = Var->getType();
+  if (CaptureType.isNull())
+    return true;
   DeclRefType = CaptureType.getNonReferenceType();
   bool Nested = false;
   bool Explicit = (Kind != TryCapture_Implicit);
diff --git a/clang/test/SemaCXX/lambda-invalid-capture.cpp b/clang/test/SemaCXX/lambda-invalid-capture.cpp
index 236753871d7018b..b77a844cfbbda50 100644
--- a/clang/test/SemaCXX/lambda-invalid-capture.cpp
+++ b/clang/test/SemaCXX/lambda-invalid-capture.cpp
@@ -23,3 +23,9 @@ int pr43080(int i) { // expected-note {{declared here}}
       i; // expected-error {{variable 'i' cannot be implicitly captured in a lambda with no capture-default specified}}
   }();
 }
+
+void pr72198() {
+  int [_, b] = {0, 0}; // expected-error{{decomposition declaration cannot be declared with type 'int'; declared type must be 'auto' or reference to 'auto'}} \
+                          expected-error{{excess elements in scalar initializer}}
+  [b]{}; // expected-warning{{expression result unused}}
+}

[zyn0217]

Could you please explain why the CaptureType might be null at the time when exercising tryCaptureVariable? I'm worried that doing so would hide a more significant issue.

[tbaederr]

Suggested change

	int [_, b] = {0, 0}; // expected-error{{decomposition declaration cannot be declared with type 'int'; declared type must be 'auto' or reference to 'auto'}} \
	expected-error{{excess elements in scalar initializer}}
	[b]{}; // expected-warning{{expression result unused}}
	int [_, b] = {0, 0}; // expected-error {{decomposition declaration cannot be declared with type 'int'; declared type must be 'auto' or reference to 'auto'}} \
	expected-error {{excess elements in scalar initializer}}
	[b]{}; // expected-warning {{expression result unused}}

[shafik]

I am not sure this is the right fix. I think by the time we are here we should have caught any errors. I made a comment in the bug report describing my alternative.

[ecnelises]

Abandon in favor of #72428