Fixed a bug that resulted in incorrect type evaluation when calling a…

… generic class constructor from within that class implementation. This addresses #3927.
microsoft · Sep 19, 2022 · b5e461b · b5e461b
1 parent 92b90d2
commit b5e461b
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Showing 3 changed files with 35 additions and 6 deletions.
diff --git a/packages/pyright-internal/src/analyzer/typeUtils.ts b/packages/pyright-internal/src/analyzer/typeUtils.ts
@@ -2668,7 +2668,7 @@ class TypeVarTransformer {
             // _pendingTypeVarTransformations set.
             const typeVarName = TypeVarType.getNameWithScope(type);
             if (!this._pendingTypeVarTransformations.has(typeVarName)) {
-                replacementType = this.transformTypeVar(type);
+                replacementType = this.transformTypeVar(type) ?? type;
 
                 if (!this._isTransformingTypeArg) {
                     this._pendingTypeVarTransformations.add(typeVarName);
@@ -2739,7 +2739,7 @@ class TypeVarTransformer {
         return type;
     }
 
-    transformTypeVar(typeVar: TypeVarType): Type {
+    transformTypeVar(typeVar: TypeVarType): Type | undefined {
         return typeVar;
     }
 
@@ -2840,7 +2840,8 @@ class TypeVarTransformer {
                 } else {
                     const typeParamName = TypeVarType.getNameWithScope(typeParam);
                     if (!this._pendingTypeVarTransformations.has(typeParamName)) {
-                        replacementType = this.transformTypeVar(typeParam);
+                        const transformedType = this.transformTypeVar(typeParam);
+                        replacementType = transformedType ?? typeParam;
 
                         if (replacementType !== typeParam) {
                             if (!this._isTransformingTypeArg) {
@@ -2849,6 +2850,8 @@ class TypeVarTransformer {
                                 this._pendingTypeVarTransformations.delete(typeParamName);
                             }
 
+                            specializationNeeded = true;
+                        } else if (transformedType !== undefined && !classType.typeArguments) {
                             specializationNeeded = true;
                         }
                     }
@@ -3147,7 +3150,7 @@ class ApplySolvedTypeVarsTransformer extends TypeVarTransformer {
             }
         }
 
-        return typeVar;
+        return undefined;
     }
 
     override transformUnionSubtype(preTransform: Type, postTransform: Type): Type | undefined {

diff --git a/packages/pyright-internal/src/tests/samples/genericTypes94.py b/packages/pyright-internal/src/tests/samples/genericTypes94.py
@@ -2,7 +2,7 @@
 # specialized with type variables in a recursive manner.
 
 from dataclasses import dataclass
-from typing import Callable, Generic, TypeVar
+from typing import Callable, Generic, Iterable, Iterator, TypeVar, overload
 
 S = TypeVar("S")
 T = TypeVar("T")
@@ -54,3 +54,29 @@ def method1(self, val: U) -> "ClassC[U, S]":
         else:
             return ClassC(self.value)
 
+
+T_co = TypeVar("T_co", covariant=True)
+
+class ClassD(Generic[T_co]):
+    @overload
+    def __init__(self, arg: Iterable[T_co]) -> None:
+        ...
+
+    @overload
+    def __init__(self, arg: Callable[[], Iterable[T_co]]) -> None:
+        ...
+
+    def __init__(self, arg: Iterable[T_co] | Callable[[], Iterable[T_co]]) -> None:
+        ...
+
+    def __iter__(self) -> Iterator[T_co]:
+        ...
+
+
+class ClassE(ClassD[T_co]):
+    def method(self) -> "ClassE[ClassE[T_co]]":
+        def inner():
+            for x in self:
+                yield ClassE(lambda: [x])
+
+        return ClassE(inner)
diff --git a/packages/pyright-internal/src/tests/samples/memberAccess14.py b/packages/pyright-internal/src/tests/samples/memberAccess14.py
@@ -52,7 +52,7 @@ class D(C[float]):
     ...
 
 
-reveal_type(C.prop, expected_text="CachedSlotProperty[Self@C[T@C], int]")
+reveal_type(C.prop, expected_text="CachedSlotProperty[C[T@C], int]")
 reveal_type(D.prop, expected_text="CachedSlotProperty[D, int]")