[clang] [C2y] Implement WG14 N3622 static used in an inline (PR #162877)

[Erich Keane via cfe-commits]

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@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -verify=good -pedantic -Wall -std=c2y %s
+// RUN: %clang_cc1 -verify -pedantic -Wall -std=c23 %s
+// RUN: %clang_cc1 -verify -pedantic -Wall -std=c17 %s
+// good-no-diagnostics
+
+/* WG14 N3622: Clang 22
+ * Allow calling static inline within extern inline
+ *
+ * This verifies that a constraint from previous standards is no longer
+ * triggered in C2y mode. The constraint is with calling a statric function
+ * or using a static variable from an inline function with external linkage.
+ */
+
+static void static_func(void) {} // expected-note {{declared here}}
+static int static_var;           // expected-note {{declared here}}
+
+extern inline void test(void) {
+  static_func();   // expected-warning {{static function 'static_func' is used in an inline function with external linkage}}
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erichkeane wrote:

Sure, I'm more pointing out: This is now an 'extension' warning, isn't it?  You can word it however you think sounds right, but since this is now allowed in C2y, and was previously being allowed 'as an extension', it is now a C2y extension, right?

https://github.com/llvm/llvm-project/pull/162877