Fixed false positive when a TypeVar appears within a function type comment. This addresses #7854. (#7856)

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

@@ -2515,6 +2515,17 @@ export class Checker extends ParseTreeWalker {
             nameWalker.walk(node.returnTypeAnnotation);
         }
 
+        if (node.functionAnnotationComment) {
+            node.functionAnnotationComment.paramTypeAnnotations.forEach((expr) => {
+                nameWalker.walk(expr);
+            });
+
+            if (node.functionAnnotationComment.returnTypeAnnotation) {
+                exemptBoundTypeVar = false;
+                nameWalker.walk(node.functionAnnotationComment.returnTypeAnnotation);
+            }
+        }
+
         localTypeVarUsage.forEach((usage) => {
             // Report error for local type variable that appears only once.
             if (usage.nodes.length === 1 && !usage.isExempt) {

packages/pyright-internal/src/tests/samples/functionAnnotation3.py

@@ -11,15 +11,15 @@ class ClassA:
     foo: str
 
     def method0(self, a, b):
-        # type: (_T, str, ClassB) -> str
+        # type: (_T, str, list[_T]) -> str
         return self.foo
 
     def method1(self, a, b):
-        # type: (_T, str, int) -> ClassB
+        # type: (_T, str, list[_T]) -> ClassB
         return ClassB()
 
     # Too many annotations
-    def method2(self, a, b):  # type: (_T, str, int, int) -> str
+    def method2(self, a, b):  # type: (_T, str, int, list[_T]) -> str
         return ""
 
     # Too few annotations
@@ -33,5 +33,4 @@ class ClassA:
         return self.foo
 
 
-class ClassB:
-    ...
+class ClassB: ...

packages/pyright-internal/src/tests/samples/typeVar9.py

@@ -120,3 +120,29 @@ _T2 = TypeVar("_T2", default=int)
 
 class ClassB(Generic[_T2]):
     def __init__(self, x: _T2 = ...) -> None: ...
+
+
+# This should generate an error because _T appears only once.
+def f17(
+    arg,  # type: _T
+):  # type: (...) -> int
+    return 1
+
+
+def f18(
+    arg,  # type: _T
+):  # type: (...) -> _T
+    return arg
+
+
+# This should generate an error because _T appears only once.
+def f19(
+    arg,
+):  # type: (_T) -> int
+    return 1
+
+
+def f20(
+    arg,  # type: _T
+):  # type: (...) -> _T
+    return arg

packages/pyright-internal/src/tests/typeEvaluator7.test.ts

@@ -814,7 +814,7 @@ test('TypeVar8', () => {
 test('TypeVar9', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typeVar9.py']);
 
-    TestUtils.validateResults(analysisResults, 11);
+    TestUtils.validateResults(analysisResults, 13);
 });
 
 test('TypeVar10', () => {