Fixed #10558 (False positive; Searching before insertion in a loop is needed)

lib/checkstl.cpp

@@ -1593,8 +1593,19 @@ void CheckStl::checkFindInsert()
 
 void CheckStl::checkFindInsertError(const Token *tok)
 {
+    std::string replaceExpr;
+    if (tok && Token::simpleMatch(tok->astParent(), "=") && tok == tok->astParent()->astOperand2() && Token::simpleMatch(tok->astParent()->astOperand1(), "[")) {
+        replaceExpr = " Instead of '" + tok->astParent()->expressionString() + "' consider using '" +
+                      tok->astParent()->astOperand1()->astOperand1()->expressionString() +
+                      (mSettings->standards.cpp < Standards::CPP17 ? ".insert(" : ".emplace(") +
+                      tok->astParent()->astOperand1()->astOperand2()->expressionString() +
+                      ", " +
+                      tok->expressionString() +
+                      ");'.";
+    }
+
     reportError(
-        tok, Severity::performance, "stlFindInsert", "Searching before insertion is not necessary.", CWE398, Certainty::normal);
+        tok, Severity::performance, "stlFindInsert", "Searching before insertion is not necessary." + replaceExpr, CWE398, Certainty::normal);
 }
 
 /**

test/teststl.cpp

@@ -5152,6 +5152,17 @@ private:
             check(code, true, Standards::CPP17);
             ASSERT_EQUALS("[test.cpp:3]: (performance) Searching before insertion is not necessary.\n", errout.str());
         }
+
+        check("void foo() {\n"
+              "   std::map<int, int> x;\n"
+              "   int data = 0;\n"
+              "   for(int i=0; i<10; ++i) {\n"
+              "      data += 123;\n"
+              "      if(x.find(5) == x.end())\n"
+              "         x[5] = data;\n"
+              "   }\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:7]: (performance) Searching before insertion is not necessary. Instead of 'x[5]=data' consider using 'x.emplace(5, data);'.\n", errout.str());
     }
 
     void checkKnownEmptyContainer() {