Fix #12450 Assert failure in ExpressionAnalyzer() (#5992)

Author: chrchr-github

lib/symboldatabase.cpp

@@ -1623,7 +1623,10 @@ namespace {
             return;
         const Token* op2 = tok->astParent()->astOperand2();
         if (op2 && op2->exprId() == 0 &&
-            !(isLambdaCaptureList(op2) || (op2->str() == "(" && isLambdaCaptureList(op2->astOperand1())) || Token::simpleMatch(op2, "{ }")))
+            !((tok->astParent()->astParent() && tok->astParent()->isAssignmentOp() && tok->astParent()->astParent()->isAssignmentOp()) ||
+              isLambdaCaptureList(op2) ||
+              (op2->str() == "(" && isLambdaCaptureList(op2->astOperand1())) ||
+              Token::simpleMatch(op2, "{ }")))
             return;
 
         if (tok->astParent()->isExpandedMacro() || Token::Match(tok->astParent(), "++|--")) {

test/testvarid.cpp

@@ -244,6 +244,7 @@ class TestVarID : public TestFixture {
         TEST_CASE(exprid7);
         TEST_CASE(exprid8);
         TEST_CASE(exprid9);
+        TEST_CASE(exprid10);
 
         TEST_CASE(structuredBindings);
     }
@@ -4028,6 +4029,19 @@ class TestVarID : public TestFixture {
         ASSERT_EQUALS(expected, tokenizeExpr(code));
     }
 
+    void exprid10()
+    {
+        const char code[] = "void f(const std::string& p) {\n" // #12350
+                            "    std::string s;\n"
+                            "    ((s = \"abc\") += p) += \"def\";\n"
+                            "}\n";
+        const char expected[] = "1: void f ( const std :: string & p ) {\n"
+                                "2: std ::@UNIQUE string s@2 ;\n"
+                                "3: ( ( s@2 =@UNIQUE \"abc\" ) +=@UNIQUE p@1 ) +=@UNIQUE \"def\"@UNIQUE ;\n"
+                                "4: }\n";
+        ASSERT_EQUALS(expected, tokenizeExpr(code));
+    }
+
     void structuredBindings() {
         const char code[] = "int foo() { auto [x,y] = xy(); return x+y; }";
         ASSERT_EQUALS("1: int foo ( ) { auto [ x@1 , y@2 ] = xy ( ) ; return x@1 + y@2 ; }\n",