Fix #13838 FP variableScope with stuctured binding (#7521)

Co-authored-by: chrchr-github <[email protected]>

Author: chrchr-github

lib/astutils.cpp

@@ -1163,7 +1163,7 @@ static bool hasUnknownVars(const Token* startTok)
 
 bool isStructuredBindingVariable(const Variable* var)
 {
-    if (!var)
+    if (!var || var->isArray())
         return false;
     const Token* tok = var->nameToken();
     while (tok && Token::Match(tok->astParent(), "[|,|:"))

lib/checkother.cpp

@@ -1093,6 +1093,9 @@ void CheckOther::checkVariableScope()
 
         if (var->nameToken()->isExpandedMacro())
             continue;
+        if (isStructuredBindingVariable(var) && // warn for single decomposition
+            !(Token::simpleMatch(var->nameToken()->astParent(), "[") && var->nameToken()->astParent()->astOperand2() == var->nameToken()))
+            continue;
 
         const bool isPtrOrRef = var->isPointer() || var->isReference();
         const bool isSimpleType = var->typeStartToken()->isStandardType() || var->typeStartToken()->isEnumType() || (var->typeStartToken()->isC() && var->type() && var->type()->isStructType());

test/testother.cpp

@@ -106,6 +106,7 @@ class TestOther : public TestFixture {
         TEST_CASE(varScope40);
         TEST_CASE(varScope41);      // #11845
         TEST_CASE(varScope42);
+        TEST_CASE(varScope43);
 
         TEST_CASE(oldStylePointerCast);
         TEST_CASE(invalidPointerCast);
@@ -1874,6 +1875,28 @@ class TestOther : public TestFixture {
         ASSERT_EQUALS("[test.cpp:3:17]: (style) The scope of the variable 's' can be reduced. [variableScope]\n", errout_str());
     }
 
+    void varScope43() {
+        check("struct S { int a, b; };\n" // #13838
+              "int f(S s) {\n"
+              "    auto& [x, y] = s;\n"
+              "    if (x < 5) {\n"
+              "        return y;\n"
+              "    }\n"
+              "    return 0;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+
+        check("struct S { int a; };\n"
+              "int f(S s) {\n"
+              "    auto& [x] = s;\n"
+              "    if (y) {\n"
+              "        return x;\n"
+              "    }\n"
+              "    return 0;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3:12]: (style) The scope of the variable 'x' can be reduced. [variableScope]\n", errout_str());
+    }
+
 #define checkOldStylePointerCast(...) checkOldStylePointerCast_(__FILE__, __LINE__, __VA_ARGS__)
     template<size_t size>
     void checkOldStylePointerCast_(const char* file, int line, const char (&code)[size], Standards::cppstd_t std = Standards::CPPLatest) {