Added small performance optimization in checker to avoid generating a diagnostic message in cases where it won't be used.

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

@@ -4942,21 +4942,24 @@ export class Checker extends ParseTreeWalker {
                         );
                     }
                 } else if (!FunctionType.isAbstractMethod(functionType)) {
+                    // If the function consists entirely of "...", assume that it's
+                    // an abstract method or a protocol method and don't require that
+                    // the return type matches. This check can also be skipped for an overload.
+                    const isEmptySuite =
+                        ParseTreeUtils.isSuiteEmpty(node.d.suite) || FunctionType.isOverloaded(functionType);
+
                     // Make sure that the function doesn't implicitly return None if the declared
                     // type doesn't allow it. Skip this check for abstract methods.
-                    const diagAddendum = new DiagnosticAddendum();
+                    const diagAddendum = isEmptySuite ? undefined : new DiagnosticAddendum();
 
                     // If the declared type isn't compatible with 'None', flag an error.
                     if (!this._evaluator.assignType(declaredReturnType, this._evaluator.getNoneType(), diagAddendum)) {
-                        // If the function consists entirely of "...", assume that it's
-                        // an abstract method or a protocol method and don't require that
-                        // the return type matches. This check can also be skipped for an overload.
-                        if (!ParseTreeUtils.isSuiteEmpty(node.d.suite) && !FunctionType.isOverloaded(functionType)) {
+                        if (!isEmptySuite) {
                             this._evaluator.addDiagnostic(
                                 DiagnosticRule.reportReturnType,
                                 LocMessage.returnMissing().format({
                                     returnType: this._evaluator.printType(declaredReturnType),
-                                }) + diagAddendum.getString(),
+                                }) + diagAddendum?.getString(),
                                 returnAnnotation
                             );
                         }