Issue8054 (#8055)

* Fixed bug that results in a false negative when solving a type variable that involves an invariant context.

* Fixed a bug that can result in incorrect type inference for a subexpression that is part of an assignment expression if executed with an inference context (bidirectional type inference). This addresses #8054.

packages/pyright-internal/src/analyzer/typeEvaluator.ts

@@ -14622,11 +14622,11 @@ export function createTypeEvaluator(
             assert(node.nodeType === ParseNodeType.ComprehensionIf);
 
             // Evaluate the test expression to validate it and mark symbols
-            // as referenced. Don't bother doing this if we're in speculative
-            // mode because it doesn't affect the element type.
-            if (!isSpeculativeModeInUse(node.testExpression)) {
-                getTypeOfExpression(node.testExpression);
-            }
+            // as referenced. This doesn't affect the type of the evalauted
+            // comprehension, but it is important for evaluating intermediate
+            // expressions such as assignment expressions that can affect other
+            // subexpressions.
+            getTypeOfExpression(node.testExpression);
         }
 
         return isIncomplete;
@@ -19721,7 +19721,7 @@ export function createTypeEvaluator(
                 }
 
                 case ParseNodeType.AssignmentExpression: {
-                    getTypeOfExpression(curNode);
+                    evaluateTypesForExpressionInContext(curNode);
                     return;
                 }
 

packages/pyright-internal/src/tests/samples/comprehension8.py

@@ -9,7 +9,7 @@ class ClassA:
     output: str
 
 
-def func1(foo: ClassA):
-    foo.output = "".join(
-        stripped for line in foo.input.splitlines() if (stripped := line.strip())
+def func1(a: ClassA, x: str):
+    a.output = x.join(
+        stripped for line in a.input.splitlines() if (stripped := line.strip())
     )