Fixed augmented assignment inspection for non-commutative operations on weak union types (PY-7605)

python/src/com/jetbrains/python/inspections/PyAugmentAssignmentInspection.java

@@ -74,7 +74,7 @@ public class PyAugmentAssignmentInspection extends PyInspection {
         if ((operations.contains(op) && !changedParts) || (changedParts && commutativeOperations.contains(op))) {
           if (leftExpression instanceof PyReferenceExpression || leftExpression instanceof PySubscriptionExpression) {
             final PyType type = myTypeEvalContext.getType(rightExpression);
-            if (type != null) {
+            if (type != null && !PyTypeChecker.isUnknown(type)) {
               final PyBuiltinCache cache = PyBuiltinCache.getInstance(rightExpression);
               final LanguageLevel languageLevel = LanguageLevel.forElement(rightExpression);
               if (isNumeric(type, cache) || (isString(type, cache, languageLevel) && !changedParts)) {

python/testData/inspections/PyAugmentAssignmentInspection/strOrUnknownFirstArg.py

@@ -0,0 +1,7 @@
+def foo(c, x, y):
+    if c:
+        z = x
+    else:
+        z = ''
+    y = z + y  # pass
+    return y

python/testSrc/com/jetbrains/python/inspections/PyAugmentAssignmentInspectionTest.java

@@ -47,6 +47,11 @@ public class PyAugmentAssignmentInspectionTest extends PyTestCase {
     doTest();
   }
 
+  // PY-7605
+  public void testStrOrUnknownFirstArg() {
+    doTest();
+  }
+
   private void doTest() {
     myFixture.configureByFile("inspections/PyAugmentAssignmentInspection/" + getTestName(true) + ".py");
     myFixture.enableInspections(PyAugmentAssignmentInspection.class);