fix #25794, infer parameter type from default value, in AST summaries

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

Index: pkg/analyzer/lib/src/summary/summarize_ast.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_ast.dart b/pkg/analyzer/lib/src/summary/summarize_ast.dart
index c2a625bf29f69a2ab264da555505f6866af128cf..cb799b93f1a36a4d4e23ed2b08b9605c5406287d 100644
--- a/pkg/analyzer/lib/src/summary/summarize_ast.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_ast.dart
@@ -643,11 +643,17 @@ class _SummarizeAstVisitor extends RecursiveAstVisitor {
       b.parameters = formalParameters.parameters
           .map((FormalParameter p) => p.accept(this))
           .toList();
-      if (!isSemanticallyStatic) {
-        for (int i = 0; i < formalParameters.parameters.length; i++) {
-          if (!b.parameters[i].isFunctionTyped &&
-              b.parameters[i].type == null) {
-            b.parameters[i].inferredTypeSlot = assignSlot();
+
+      for (int i = 0; i < formalParameters.parameters.length; i++) {
+        UnlinkedParamBuilder p = b.parameters[i];
+        if (!p.isFunctionTyped && p.type == null) {
+          // Strong mode infers parameters in two cases:
+          // - instance members (i.e. not semantically static),
+          // - parameters with default values, except initializing formals
+          //   (the type comes from the field).
+          if (!isSemanticallyStatic ||
+              p.initializer != null && !p.isInitializingFormal) {
+            p.inferredTypeSlot = assignSlot();
           }
         }
       }