Fixed a bug that results in a false positive error when assigning a t…

…uple of indeterminate length to a zero-length tuple target. This addresses #9866. (#9867)
microsoft · Feb 10, 2025 · ed53f3e · ed53f3e
1 parent 131f56d
commit ed53f3e
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Showing 3 changed files with 16 additions and 1 deletion.
diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -3873,6 +3873,11 @@ export function createTypeEvaluator(
                             sourceEntryTypes.splice(unboundedIndex, 0, typeToReplicate);
                         }
                     }
+
+                    if (sourceEntryTypes.length > targetTypes.length) {
+                        // Remove elements to make the count match the target count.
+                        sourceEntryTypes.splice(unboundedIndex, 1);
+                    }
                 }
 
                 // If there's an unpack operator in the target and we have too many source elements,

diff --git a/packages/pyright-internal/src/tests/samples/tuple6.py b/packages/pyright-internal/src/tests/samples/tuple6.py
@@ -54,3 +54,13 @@ def func1(p1: tuple[str, ...]):
     a, b = p1
 
     c, d, *f = p1
+
+
+def func2(p1: tuple[str, ...], p2: tuple[str, *tuple[str, ...]]):
+    () = p1
+    (_,) = p1
+    (_, _) = p1
+
+    # This should generate an error.
+    () = p2
+    (_,) = p2
diff --git a/packages/pyright-internal/src/tests/typeEvaluator8.test.ts b/packages/pyright-internal/src/tests/typeEvaluator8.test.ts
@@ -470,7 +470,7 @@ test('Tuple5', () => {
 test('Tuple6', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['tuple6.py']);
 
-    TestUtils.validateResults(analysisResults, 9);
+    TestUtils.validateResults(analysisResults, 10);
 });
 
 test('Tuple7', () => {