Fixed a bug that led to a false positive error when a frozen dataclas…

…s has an explicit `__eq__` method and is used in way that requires it to be `Hashable`. This addresses #5928.
microsoft · Sep 11, 2023 · f330161 · f330161
1 parent 46f5351
commit f330161
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Showing 4 changed files with 30 additions and 3 deletions.
diff --git a/packages/pyright-internal/src/analyzer/dataClasses.ts b/packages/pyright-internal/src/analyzer/dataClasses.ts
@@ -623,8 +623,7 @@ export function synthesizeDataClassMethods(
         });
     }
 
-    let synthesizeHashFunction =
-        !ClassType.isSkipSynthesizedDataClassEq(classType) && ClassType.isFrozenDataClass(classType);
+    let synthesizeHashFunction = ClassType.isFrozenDataClass(classType);
     const synthesizeHashNone =
         !ClassType.isSkipSynthesizedDataClassEq(classType) && !ClassType.isFrozenDataClass(classType);
 

diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -16409,7 +16409,10 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
 
                 let skipSynthesizeHash = false;
                 const hashSymbol = lookUpClassMember(classType, '__hash__', ClassMemberLookupFlags.SkipBaseClasses);
-                if (hashSymbol) {
+
+                // If there is a hash symbol defined in the class (i.e. one that we didn't
+                // synthesize above), then we shouldn't synthesize a new one for the dataclass.
+                if (hashSymbol && !hashSymbol.symbol.getSynthesizedType()) {
                     skipSynthesizeHash = true;
                 }
 

diff --git a/packages/pyright-internal/src/analyzer/typeGuards.ts b/packages/pyright-internal/src/analyzer/typeGuards.ts
@@ -2456,3 +2456,17 @@ function narrowTypeForCallable(
         }
     });
 }
+
+export class Animal {}
+export class Dog extends Animal {}
+
+export class Plant {}
+export class Tree extends Plant {}
+
+export function func1(val: Animal) {
+    if (val instanceof Tree) {
+        console.log(val);
+    } else {
+        console.log(val);
+    }
+}
diff --git a/packages/pyright-internal/src/tests/samples/dataclassHash1.py b/packages/pyright-internal/src/tests/samples/dataclassHash1.py
@@ -55,3 +55,14 @@ def __hash__(self) -> int:
 
 
 v6: Hashable = DC6(0)
+
+
+@dataclass(frozen=True)
+class DC7:
+    a: int
+
+    def __eq__(self, other) -> bool:
+        return self.a == other.a
+
+
+v7: Hashable = DC7(0)