fix reportUnsafeMultipleInheritance false positive in diamond inher…

…itance scenarios, which is safe due to how MRO works
DetachHead · Dec 9, 2024 · 1040794 · 1040794
1 parent 2fd23b1
commit 1040794
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diff --git a/packages/pyright-internal/src/analyzer/checker.ts b/packages/pyright-internal/src/analyzer/checker.ts
@@ -5712,6 +5712,7 @@ export class Checker extends ParseTreeWalker {
         }
         /** if it's a dataclass then no further base classes in the MRO can have constructors */
         let constructorIsSafe = !this._isDataclassWithGeneratedConstructor(classType);
+        const uniqueBaseClasses = new Set<ClassType>();
         const baseClassesWithPossiblyUncalledConstructors: ClassType[] = [];
         const isTypedDict = ClassType.isTypedDictClass(classType);
         const diagAddendum = new DiagnosticAddendum();
@@ -5732,12 +5733,15 @@ export class Checker extends ParseTreeWalker {
                         constructorMethodResult &&
                         constructorMethodResult.classType &&
                         isClass(constructorMethodResult.classType) &&
+                        // prevent the same base class from being checked twice which can happen in diamond inheritance situations
+                        !uniqueBaseClasses.has(constructorMethodResult.classType) &&
                         // synthesized dataclass constructors are safe as the runtime machinery seems to account for multiple inheritance moments
                         !(
                             isFunction(constructorMethodResult.type) &&
                             FunctionType.isSynthesizedMethod(constructorMethodResult.type)
                         )
                     ) {
+                        uniqueBaseClasses.add(constructorMethodResult.classType);
                         if (constructorIsSafe) {
                             constructorIsSafe = false;
                         } else {

diff --git a/packages/pyright-internal/src/tests/samples/multipleInheritance.py b/packages/pyright-internal/src/tests/samples/multipleInheritance.py
@@ -57,4 +57,16 @@ class U(A, C): # error
 
 @dataclass(init=False)
 class V(A, C): # no error
-    ...
+    ...
+
+class Up:
+    def __init__(self): ...
+
+
+class Left(Up): ...
+
+
+class Right(Up): ...
+
+
+class Down(Left, Right): ...  # no error