Fixed a bug that masked an error (false negative) under certain circu…

…mstances when evaluating a lambda. This addresses microsoft#7012. (microsoft#7059)
Domma143 · Jan 20, 2024 · af44054 · af44054
1 parent 50f677c
commit af44054
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Showing 3 changed files with 16 additions and 2 deletions.
diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -14059,6 +14059,8 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
             },
             {
                 dependentType: expectedType,
+                allowDiagnostics:
+                    !forceSpeculative && !isDiagnosticSuppressedForNode(node) && !inferenceContext?.isTypeIncomplete,
             }
         );
 

diff --git a/packages/pyright-internal/src/tests/samples/lambda4.py b/packages/pyright-internal/src/tests/samples/lambda4.py
@@ -1,7 +1,7 @@
 # This sample tests the case where a lambda is assigned to
 # a union type that contains multiple callables.
 
-from typing import Callable, Protocol
+from typing import Callable, Protocol, TypeVar
 
 
 U1 = Callable[[int, str], bool] | Callable[[str], bool]
@@ -68,3 +68,15 @@ def accepts_u2(cb: U2) -> U2:
 accepts_u2(callback_1)
 accepts_u2(callback_2)
 accepts_u2(callback_3)
+
+
+T = TypeVar("T")
+
+Takes = Callable[[T], object]
+
+U3 = Takes[Takes[int]] | Takes[Takes[str]]
+
+
+def accepts_u3(u: U3):
+    # This should generate an error.
+    u(lambda v: v.lower())
diff --git a/packages/pyright-internal/src/tests/typeEvaluator1.test.ts b/packages/pyright-internal/src/tests/typeEvaluator1.test.ts
@@ -685,7 +685,7 @@ test('Lambda3', () => {
 test('Lambda4', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['lambda4.py']);
 
-    TestUtils.validateResults(analysisResults, 1);
+    TestUtils.validateResults(analysisResults, 2);
 });
 
 test('Lambda5', () => {