[clang] [-Wunsafe-buffer-usage] Fix a bug that wrongly assumed CXXMethodDecl always has an identifier (PR #137248)

[Jan Korous via cfe-commits]

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@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -std=c++20 -Wno-all -Wunsafe-buffer-usage \
+// RUN:            -verify %s
+
+// This example uncovered a bug in UnsafeBufferUsage.cpp, where the
+// code assumed that a CXXMethodDecl always have an identifier.
+
+int printf( const char* format, char *); // <-- Fake decl of `printf`; to reproduce the bug, this example needs an implicit cast within a printf call.
+
+namespace std { // fake std namespace; to reproduce the bug, a CXXConversionDecl needs to be in std namespace.
+  class X {
+    char * p;
+  public:    
+    operator char*() {return p;}
+  };
+
+  class Y {
+  public:
+    X x;
+  };
+
+}
+
+void test(std::Y &y) {
+  // Here `y.x` involves an implicit cast and calls the conversion overloading, which has no identifier:
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jkorous-apple wrote:

nit: "calls the overloaded cast operator"

https://github.com/llvm/llvm-project/pull/137248