Fixed a bug that led to incorrect type narrowing on assignment in cer…

…tain cases. This addresses #5757. (#5761) Co-authored-by: Eric Traut <[email protected]>
microsoft · Aug 18, 2023 · b9f4615 · b9f4615
1 parent 5543a9f
commit b9f4615
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -24385,6 +24385,14 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
             }
         }
 
+        // If the declared and assigned types are the same generic type but the assigned type
+        // contains one or more unknowns, use the declared type instead.
+        if (ClassType.isSameGenericClass(declaredType, assignedType)) {
+            if (containsAnyRecursive(assignedType) && !containsAnyRecursive(declaredType)) {
+                return declaredType;
+            }
+        }
+
         return undefined;
     }
 
@@ -24404,14 +24412,19 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
                         return declaredSubtype;
                     }
 
-                    // If the source is generic and has unspecified type arguments,
-                    // see if we can determine them based on the declared type.
-                    if (isClass(declaredSubtype) && isClass(assignedSubtype)) {
+                    if (
+                        isClass(declaredSubtype) &&
+                        isClass(assignedSubtype) &&
+                        TypeBase.isInstance(declaredSubtype) === TypeBase.isInstance(assignedSubtype)
+                    ) {
                         const result = replaceTypeArgsWithAny(node, declaredSubtype, assignedSubtype);
                         if (result) {
                             assignedSubtype = result;
                         }
-                    } else if (!isTypeVar(declaredSubtype) && isTypeVar(assignedSubtype)) {
+                        return assignedSubtype;
+                    }
+
+                    if (!isTypeVar(declaredSubtype) && isTypeVar(assignedSubtype)) {
                         // If the source is an unsolved TypeVar but the declared type is concrete,
                         // use the concrete type.
                         return declaredSubtype;

diff --git a/packages/pyright-internal/src/tests/samples/assignment10.py b/packages/pyright-internal/src/tests/samples/assignment10.py
@@ -66,3 +66,8 @@ def func4(y: list[Any]):
 
     x3: Iterable[Any] = y
     reveal_type(x3, expected_text="list[Any]")
+
+
+def func5(v1: list[Any | None]):
+    x1: list[int | None] = v1
+    reveal_type(x1, expected_text="list[int | None]")