[clang] [clang] move -Wcast-function-type under -Wextra (PR #77178)

[Vlad Serebrennikov via cfe-commits]

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@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 %s -fsyntax-only -Wextra -verify
+
+
+int t(int array[static 12]);
+int u(int i);
+const int v(int i); /* expected-warning {{'const' type qualifier on return type has no effec}} */
+int x(long);
+
+typedef int (f1)(long);
+typedef int (f2)(void*);
+typedef int (f3)();
+typedef void (f4)();
+typedef void (f5)(void);
+typedef int (f6)(long, int);
+typedef int (f7)(long,...);
+typedef int (f8)(int *);
+typedef int (f9)(const int);
+typedef int (f10)(int);
+
+f1 *a;
+f2 *b;
+f3 *c;
+f4 *d;
+f5 *e;
+f6 *f;
+f7 *g;
+f8 *h;
+f9 *i;
+f10 *j;
+
+void foo(void) {
+  a = (f1 *)x;
+  b = (f2 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f2 *' (aka 'int (*)(void *)') converts to incompatible function type}} */
+  c = (f3 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f3 *' (aka 'int (*)()') converts to incompatible function type}} */
+  d = (f4 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f4 *' (aka 'void (*)()') converts to incompatible function type}} */
+  e = (f5 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f5 *' (aka 'void (*)(void)') converts to incompatible function type}} */
+  f = (f6 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f6 *' (aka 'int (*)(long, int)') converts to incompatible function type}} */
+  g = (f7 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f7 *' (aka 'int (*)(long, ...)') converts to incompatible function type}} */
+  h = (f8 *)t;
+  i = (f9 *)u;
+  j = (f10 *)v; /* expected-warning {{cast from 'const int (*)(int)' to 'f10 *' (aka 'int (*)(int)') converts to incompatible function type}} */
----------------
Endilll wrote:

On line 6 we issue a diagnostic that `const` qualifier doesn't have effect on return type, yet we issue a diagnostic here telling that this makes function pointer type incompatible. It feels like we fail to make up our minds on the matter, or that we are overly pedantic without pedantic warnings enabled.

https://github.com/llvm/llvm-project/pull/77178