fix #25794, infer parameter type from default value

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 98e3de4960e5cefb996aafa6b7c50804d3aaabce..50e1bb6611b47be703cebb842e28d256f514c0ec 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -902,10 +902,14 @@ class _CompilationUnitSerializer {
     DartType type = parameter.type;
     if (parameter.hasImplicitType) {
       Element contextParent = context.enclosingElement;
+      // Strong mode infers parameters in two cases:
+      // - instance members (i.e. not constructors or static members),
+      // - parameters with default values, except initializing formals
+      //   (the type comes from the field).
       if (!parameter.isInitializingFormal &&
           contextParent is ExecutableElement &&
-          !contextParent.isStatic &&
-          contextParent is! ConstructorElement) {
+          (!contextParent.isStatic && contextParent is! ConstructorElement ||
+              parameter.parameterKind != ParameterKind.REQUIRED)) {
         b.inferredTypeSlot = storeInferredType(type, context);
       }
     } else {