Fixed #5980 (ValueFlow: pointer cant be 0 below throw in switch)

lib/valueflow.cpp

@@ -236,17 +236,28 @@ static bool bailoutSelfAssignment(const Token * const tok)
 static bool isReturn(const Token *tok)
 {
     const Token *prev = tok ? tok->previous() : nullptr;
-    if (Token::simpleMatch(prev, "}") && Token::simpleMatch(prev->link()->tokAt(-2),"} else {"))
-        return isReturn(prev) && isReturn(prev->link()->tokAt(-2));
+    if (Token::Match(prev ? prev->previous() : nullptr, "} ;"))
+        prev = prev->previous();
+
+    if (Token::simpleMatch(prev, "}")) {
+        if (Token::simpleMatch(prev->link()->tokAt(-2), "} else {"))
+            return isReturn(prev) && isReturn(prev->link()->tokAt(-2));
+        if (Token::simpleMatch(prev->link()->previous(), ") {") &&
+            Token::simpleMatch(prev->link()->linkAt(-1)->previous(), "switch (") &&
+            !Token::findsimplematch(prev->link(), "break", prev)) {
+            return true;
+        }
+    }
+
     if (Token::simpleMatch(prev, ";")) {
         // noreturn function
         if (Token::simpleMatch(prev->previous(), ") ;") && Token::Match(prev->linkAt(-1)->tokAt(-2), "[;{}] %name% ("))
             return true;
         // return/goto statement
         prev = prev->previous();
-        while (prev && !Token::Match(prev,"[;{}]"))
+        while (prev && !Token::Match(prev, ";|{|}|return|goto|throw"))
             prev = prev->previous();
-        return Token::Match(prev, "[;{}] return|goto");
+        return prev && prev->isName();
     }
     return false;
 }

test/testvalueflow.cpp

@@ -862,6 +862,17 @@ private:
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 6U, 3));
 
+        code = "int f(int *x) {\n" // #5980
+               "  if (!x) {\n"
+               "    switch (i) {\n"
+               "      default:\n"
+               "        throw std::runtime_error(msg);\n"
+               "    };\n"
+               "  }\n"
+               "  return *x;\n"  // <- x is not 0
+               "}";
+        ASSERT_EQUALS(false, testValueOfX(code, 8U, 0));
+
         // pointer/reference to x
         code = "int f(void) {\n"
                "  int x = 2;\n"