Fix #15020 FP knownConditionTrueFalse in C23 static_assert (#8841)

Author: chrchr-github

lib/checkother.cpp

@@ -2927,9 +2927,11 @@ isStaticAssert(const Settings &settings, const Token *tok)
         return true;
     }
 
-    if (tok->isC() && settings.standards.c >= Standards::C11 &&
-        Token::simpleMatch(tok, "_Static_assert")) {
-        return true;
+    if (tok->isC()) {
+        if (settings.standards.c >= Standards::C11 && Token::simpleMatch(tok, "_Static_assert"))
+            return true;
+        if (settings.standards.c >= Standards::C23 && Token::simpleMatch(tok, "static_assert"))
+            return true;
     }
 
     return false;

test/testother.cpp

@@ -7756,6 +7756,12 @@ class TestOther : public TestFixture {
               "}\n", dinit(CheckOptions, $.cpp = false));
         ASSERT_EQUALS("", errout_str());
 
+        check("void f() {\n" // #15020
+              "    enum { Four = 4 };\n"
+              "    static_assert(Four == 4, \"\");\n"
+              "}\n", dinit(CheckOptions, $.cpp = false));
+        ASSERT_EQUALS("", errout_str());
+
         check("void f() {\n"
               "    enum { Four = 4 };\n"
               "    static_assert(4 == Four, \"\");\n"