Fix #13326: FP shiftNegative for template argument

lib/astutils.cpp

@@ -3762,3 +3762,72 @@ bool isUnreachableOperand(const Token *tok)
 
     return false;
 }
+
+static bool tokenDependsOnTemplateArg(const Token *tok)
+{
+    if (!tok)
+        return false;
+    if (tok->isTemplateArg())
+        return true;
+    return tokenDependsOnTemplateArg(tok->astOperand1())
+           || tokenDependsOnTemplateArg(tok->astOperand2());
+}
+
+static void skipUnreachableIfBranch(const Token *&tok)
+{
+    const Token *condTok = tok->linkAt(-1);
+    if (!condTok)
+        return;
+
+    if (!Token::simpleMatch(condTok->tokAt(-1), "if") && !Token::simpleMatch(condTok->tokAt(-2), "if constexpr"))
+        return;
+
+    condTok = condTok->astOperand2();
+    if (!condTok)
+        return;
+
+    if ((condTok->hasKnownIntValue() && condTok->getKnownIntValue() == 0)
+        || (tokenDependsOnTemplateArg(condTok) && condTok->getValue(0))) {
+        tok = tok->link();
+    }
+}
+
+static void skipUnreachableElseBranch(const Token *&tok)
+{
+    if (Token::simpleMatch(tok->previous(), ")"))
+        return;
+
+    const Token *condTok = tok->linkAt(-2);
+    if (!condTok)
+        return;
+
+    condTok = condTok->linkAt(-1);
+    if (!condTok)
+        return;
+
+    if (!Token::simpleMatch(condTok->tokAt(-1), "if") && !Token::simpleMatch(condTok->tokAt(-2), "if constexpr"))
+        return;
+
+    condTok = condTok->astOperand2();
+
+    if ((condTok->hasKnownIntValue() && condTok->getKnownIntValue() != 0)
+        || (tokenDependsOnTemplateArg(condTok) && !condTok->getValue(0))) {
+        tok = tok->link();
+    }
+}
+
+void skipUnreachableBranch(const Token *&tok)
+{
+    if (!Token::simpleMatch(tok, "{"))
+        return;
+
+    if (tok->scope()->type == Scope::ScopeType::eIf) {
+        skipUnreachableIfBranch(tok);
+        return;
+    }
+
+    if (tok->scope()->type == Scope::ScopeType::eElse) {
+        skipUnreachableElseBranch(tok);
+        return;
+    }
+}

lib/astutils.h

@@ -450,4 +450,6 @@ bool isExhaustiveSwitch(const Token *startbrace);
 
 bool isUnreachableOperand(const Token *tok);
 
+void skipUnreachableBranch(const Token *&tok);
+
 #endif // astutilsH

lib/checkother.cpp

@@ -3114,6 +3114,8 @@ void CheckOther::checkNegativeBitwiseShift()
     logChecker("CheckOther::checkNegativeBitwiseShift");
 
     for (const Token* tok = mTokenizer->tokens(); tok; tok = tok->next()) {
+        skipUnreachableBranch(tok);
+
         if (!tok->astOperand1() || !tok->astOperand2())
             continue;
 

test/testother.cpp

@@ -9369,6 +9369,35 @@ class TestOther : public TestFixture {
               "    }\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        // #13326
+        check("template<int b>\n"
+              "int f(int a)\n"
+              "{\n"
+              "    if constexpr (b >= 0) {\n"
+              "        return a << b;\n"
+              "    } else {\n"
+              "        return a << -b;\n"
+              "    }\n"
+              "}\n"
+              "int g() {\n"
+              "    return f<1>(2)\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+
+        check("template<int b>\n"
+              "int f(int a)\n"
+              "{\n"
+              "    if constexpr (b >= 0) {\n"
+              "        return a << b;\n"
+              "    } else {\n"
+              "        return a << -b;\n"
+              "    }\n"
+              "}\n"
+              "int g() {\n"
+              "    return f<-1>(2)\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void incompleteArrayFill() {