Fix #13544 FN unreachableCode / Fixup #13491 FP unreachableCode for declaration in switch (#7219)

Author: chrchr-github

lib/checkother.cpp

@@ -871,8 +871,21 @@ static bool isVardeclInSwitch(const Token* tok)
         return false;
     if (!isNestedInSwitch(tok->scope()))
         return false;
-    const Token* end = Token::findsimplematch(tok, ";");
-    return end && end->previous()->variable() && end->previous()->variable()->nameToken() == end->previous();
+    if (const Token* end = Token::findsimplematch(tok, ";")) {
+        for (const Token* tok2 = tok; tok2 != end; tok2 = tok2->next()) {
+            if (tok2->isKeyword() && tok2->str() == "case")
+                return false;
+            if (tok2->variable() && tok2->variable()->nameToken() == tok2) {
+                end = tok2->scope()->bodyEnd;
+                for (const Token* tok3 = tok2; tok3 != end; tok3 = tok3->next()) {
+                    if (tok3->isKeyword())
+                        return tok3->str() == "case";
+                }
+                return false;
+            }
+        }
+    }
+    return false;
 }
 
 //---------------------------------------------------------------------------

test/testother.cpp

@@ -5710,6 +5710,20 @@ class TestOther : public TestFixture {
               "}\n");
         ASSERT_EQUALS("", errout_str());
 
+        check("int f(int i) {\n"
+              "    switch (i) {\n"
+              "    case 0:\n"
+              "        return 0;\n"
+              "        int a[1];\n"
+              "    case 1:\n"
+              "    case 2:\n"
+              "        a[0] = 5;\n"
+              "        return a[0] + i;\n"
+              "    }\n"
+              "    return 3;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+
         check("int f(int i) {\n"
               "    switch (i) {\n"
               "    case 0:\n"
@@ -5780,6 +5794,18 @@ class TestOther : public TestFixture {
               "    return x;\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("bool f(int x, int y) {\n" // #13544
+              "    switch (x) {\n"
+              "    case 1: {\n"
+              "        return y != 0;\n"
+              "        int z = y + 5;\n"
+              "        return z != 7;\n"
+              "    }\n"
+              "    }\n"
+              "    return false;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:5]: (style) Statements following 'return' will never be executed.\n", errout_str());
     }