Fixed bug that results in a false negative when determining if a callable type is compatible with another callable type and the first has a *args parameter and the second has a single positional+keyword parameter. This addresses #7937. (#7938)

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

@@ -25013,6 +25013,23 @@ export function createTypeEvaluator(
                 ) {
                     canAssign = false;
                 }
+            } else if (
+                destParam.source !== ParameterSource.PositionOnly &&
+                srcParam.source === ParameterSource.PositionOnly &&
+                srcParamDetails.kwargsIndex === undefined &&
+                !srcParamDetails.params.some(
+                    (p) =>
+                        p.source === ParameterSource.KeywordOnly &&
+                        p.param.category === ParameterCategory.Simple &&
+                        p.param.name === destParam.param.name
+                )
+            ) {
+                diag?.addMessage(
+                    LocAddendum.namedParamMissingInSource().format({
+                        name: destParam.param.name ?? '',
+                    })
+                );
+                canAssign = false;
             }
         }
 

packages/pyright-internal/src/tests/samples/overload7.py

@@ -331,3 +331,31 @@ def func17(**kwargs: float) -> None: ...
 
 def func17(d: dict[str, float] | None = None, /, **kwargs: float) -> None:
     pass
+
+
+@overload
+def func18(a: int) -> int: ...
+@overload
+def func18(*args: int) -> int: ...
+
+
+# This should generate an error because the keyword parameter "a" is missing.
+def func18(*args: int) -> int: ...
+
+
+@overload
+def func19(a: int) -> int: ...
+@overload
+def func19(*args: int) -> int: ...
+
+
+def func19(*args: int, a: int = 1) -> int: ...
+
+
+@overload
+def func20(a: int) -> int: ...
+@overload
+def func20(*args: int) -> int: ...
+
+
+def func20(*args: int, **kwargs: int) -> int: ...

packages/pyright-internal/src/tests/typeEvaluator6.test.ts

@@ -58,7 +58,7 @@ test('Overload6', () => {
 
 test('Overload7', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['overload7.py']);
-    TestUtils.validateResults(analysisResults, 6);
+    TestUtils.validateResults(analysisResults, 7);
 });
 
 test('Overload8', () => {