Fix #13671 duplicated unreadVariable with assignment in variable declaration (danmar#8139)

Co-authored-by: chrchr-github <noreply@github.com>
Co-authored-by: Daniel Marjamäki <daniel.marjamaki@gmail.com>

Author: 3 people

lib/checkunusedvar.cpp

@@ -1198,6 +1198,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
         const Token *nextStructuredBindingTok = nullptr;
         std::vector<std::pair<const Token*, const Token*>> unusedStructuredBindingTokens;
         size_t structuredBindingTokCount = 0;
+        std::set<const Variable*> diagUnreadVariable; // prevent duplicate warnings
 
         for (const Token *tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
             if (nextStructuredBindingTok) {
@@ -1366,8 +1367,10 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                 if (!expr->variable() || !expr->variable()->isMaybeUnused()) {
                     if (structuredBindingTokCount > 0)
                         unusedStructuredBindingTokens.emplace_back(tok, expr);
-                    else
+                    else {
                         unreadVariableError(tok, expr->expressionString(), false);
+                        diagUnreadVariable.emplace(expr->variable());
+                    }
                 }
             }
         }
@@ -1420,7 +1423,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                      !(var->valueType() && var->valueType()->container) &&
                      !(var->isStatic() && isReturnedByRef(var, scope->function)))
                 unassignedVariableError(usage._var->nameToken(), varname);
-            else if (!usage._var->isMaybeUnused() && !usage._modified && !usage._read && var) {
+            else if (!usage._var->isMaybeUnused() && !usage._modified && !usage._read && var && diagUnreadVariable.count(usage._var) == 0) {
                 const Token* vnt = var->nameToken();
                 bool error = false;
                 if (vnt->next()->isSplittedVarDeclEq() || (!var->isReference() && vnt->strAt(1) == "=")) {

samples/unreadVariable/out.txt

@@ -1,6 +1,3 @@
 samples\unreadVariable\bad.cpp:5:34: style: Variable 's2' is assigned a value that is never used. [unreadVariable]
     std::string s1 = "test1", s2 = "test2";
                                  ^
-samples\unreadVariable\bad.cpp:5:31: style: Variable 's2' is assigned a value that is never used. [unreadVariable]
-    std::string s1 = "test1", s2 = "test2";
-                              ^