[ASTMatchers] fix captureVars assertion failure on capturesVariables

Matcher 'capturesVar' should check for capturesVariables() before
calling getCaptureVar() since it asserts this LambdaCapture does capture
a variable.

Fixes #76425

Author: danix800

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -4817,6 +4817,8 @@ AST_MATCHER_P(LambdaExpr, hasAnyCapture, internal::Matcher<LambdaCapture>,
 /// capturesVar(hasName("x")) matches `x` and `x = 1`.
 AST_MATCHER_P(LambdaCapture, capturesVar, internal::Matcher<ValueDecl>,
               InnerMatcher) {
+  if (!Node.capturesVariable())
+    return false;
   auto *capturedVar = Node.getCapturedVar();
   return capturedVar && InnerMatcher.matches(*capturedVar, Finder, Builder);
 }

clang/unittests/ASTMatchers/ASTMatchersNodeTest.cpp

@@ -2308,6 +2308,8 @@ TEST_P(ASTMatchersTest, LambdaCaptureTest_BindsToCaptureOfVarDecl) {
       matches("int main() { int cc; auto f = [=](){ return cc; }; }", matcher));
   EXPECT_TRUE(
       matches("int main() { int cc; auto f = [&](){ return cc; }; }", matcher));
+  EXPECT_TRUE(matches(
+      "void f(int a) { int cc[a]; auto f = [&](){ return cc;}; }", matcher));
 }
 
 TEST_P(ASTMatchersTest, LambdaCaptureTest_BindsToCaptureWithInitializer) {