Changed override-related checks (reportIncompatibleMethodOverride, …

…`reportIncompatibleVariableOverride` and `reportImplicitOverride`) so they apply to stub files. Previously, these were skipped for stubs. This addresses #6158. (#6159)

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

@@ -332,15 +332,14 @@ export class Checker extends ParseTreeWalker {
                 this._validateProtocolTypeParamVariance(node, classTypeResult.classType);
             }
 
-            // Skip the overrides check for stub files. Many of the built-in
-            // typeshed stub files trigger this diagnostic. Also skip the slots
-            // check because class variables declared in a stub file are
-            // interpreted as instance variables.
+            // Skip the slots check because class variables declared in a stub
+            // file are interpreted as instance variables.
             if (!this._fileInfo.isStubFile) {
-                this._validateBaseClassOverrides(classTypeResult.classType);
                 this._validateSlotsClassVarConflict(classTypeResult.classType);
             }
 
+            this._validateBaseClassOverrides(classTypeResult.classType);
+
             this._validateMultipleInheritanceBaseClasses(classTypeResult.classType, node.name);
 
             this._validateMultipleInheritanceCompatibility(classTypeResult.classType, node.name);