Fixed bug that results in incorrect evaluation of a generic dataclass…

… entry when the entry is defined by a generic subclass. This addresses #9545.
microsoft · Dec 10, 2024 · f32c0b6 · f32c0b6
1 parent e19106a
commit f32c0b6
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Showing 3 changed files with 34 additions and 5 deletions.
diff --git a/packages/pyright-internal/src/analyzer/dataClasses.ts b/packages/pyright-internal/src/analyzer/dataClasses.ts
@@ -613,6 +613,11 @@ export function synthesizeDataClassMethods(
                                 });
 
                                 defaultType = makeTypeVarsFree(defaultType, liveTypeVars);
+
+                                if (entry.mroClass && requiresSpecialization(defaultType)) {
+                                    const solution = buildSolutionFromSpecializedClass(entry.mroClass);
+                                    defaultType = applySolvedTypeVars(defaultType, solution);
+                                }
                             }
                         }
                     }
@@ -1135,7 +1140,7 @@ export function addInheritedDataClassEntries(classType: ClassType, entries: Data
 
                 // If the type from the parent class is generic, we need to convert
                 // to the type parameter namespace of child class.
-                const updatedEntry = { ...entry };
+                const updatedEntry = { ...entry, mroClass };
                 updatedEntry.type = applySolvedTypeVars(updatedEntry.type, solution);
 
                 if (entry.isClassVar) {

diff --git a/packages/pyright-internal/src/analyzer/types.ts b/packages/pyright-internal/src/analyzer/types.ts
@@ -538,6 +538,7 @@ export namespace ModuleType {
 export interface DataClassEntry {
     name: string;
     classType: ClassType;
+    mroClass?: ClassType;
     isClassVar: boolean;
     isKeywordOnly: boolean;
     alias?: string | undefined;

diff --git a/packages/pyright-internal/src/tests/samples/dataclass10.py b/packages/pyright-internal/src/tests/samples/dataclass10.py
@@ -7,15 +7,38 @@
 
 
 @dataclass
-class Foo(Generic[T]):
+class ABase(Generic[T]):
     value: Union[str, T]
 
 
-reveal_type(Foo(""), expected_text="Foo[Unknown]")
+reveal_type(ABase(""), expected_text="ABase[Unknown]")
 
 
-class Bar(Foo[int]):
+class AChild(ABase[int]):
     pass
 
 
-reveal_type(Bar(123), expected_text="Bar")
+reveal_type(AChild(123), expected_text="AChild")
+
+
+class B(Generic[T]):
+    pass
+
+
+@dataclass
+class CBase(Generic[T]):
+    x: B[T] = B[T]()
+
+
+@dataclass
+class CChild(CBase[T]):
+    pass
+
+
+c1 = CBase[int]()
+reveal_type(c1, expected_text="CBase[int]")
+reveal_type(c1.x, expected_text="B[int]")
+
+c2 = CChild[int]()
+reveal_type(c2, expected_text="CChild[int]")
+reveal_type(c2.x, expected_text="B[int]")