Clean up the use of rawType in InvocationInferrer.

In some follow-up work I'm doing with the `InvocationInferrer` class
hierarchy to support dart-lang/language#731,
I've been getting confused due to the fact that `rawType` is:

- a final field in the base class

- a non-final local variable in the
  `FullInvocationInferrer.resolveInvocation` method, which sometimes
  matches the final field and sometimes doesn't, and

- a parameter of some methods in the class hierarchy.

This change makes the field non-final and updates it as needed so that
it always matches the value of the non-final local variable in
`FullInvocationInferrer.resolveInvocation`.  (I would have preferred
to eliminate the local variable entirely, but it would have led to far
too many nuisance null checks).  It also eliminates some unnecessary
method parameters.

Change-Id: I204ef93b5e3433edb9066519ec5d01dd3dfa7f08
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/240461
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

Author: stereotype441

pkg/analyzer/lib/src/dart/resolver/invocation_inferrer.dart

@@ -173,7 +173,7 @@ abstract class FullInvocationInferrer<Node extends AstNodeImpl>
     } else if (rawType == null || rawType.typeFormals.isEmpty) {
       typeArgumentTypes = const <DartType>[];
     } else {
-      rawType = getFreshTypeParameters(rawType.typeFormals)
+      this.rawType = rawType = getFreshTypeParameters(rawType.typeFormals)
           .applyToFunctionType(rawType);
 
       inferrer = resolver.typeSystem.setupGenericTypeInference(
@@ -193,7 +193,6 @@ abstract class FullInvocationInferrer<Node extends AstNodeImpl>
     List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo =
         _isIdentical ? [] : null;
     var deferredClosures = _visitArguments(
-        rawType: rawType,
         identicalInfo: identicalInfo,
         substitution: substitution,
         inferrer: inferrer);
@@ -206,7 +205,6 @@ abstract class FullInvocationInferrer<Node extends AstNodeImpl>
               rawType!.typeFormals, inferrer.partialInfer());
         }
         _resolveDeferredClosures(
-            rawType: rawType,
             deferredClosures: stage,
             identicalInfo: identicalInfo,
             substitution: substitution,
@@ -382,7 +380,7 @@ class InvocationInferrer<Node extends AstNodeImpl> {
   final ResolverVisitor resolver;
   final Node node;
   final ArgumentListImpl argumentList;
-  final FunctionType? rawType;
+  FunctionType? rawType;
   final DartType? contextType;
   final List<WhyNotPromotedGetter> whyNotPromotedList;
 
@@ -403,10 +401,9 @@ class InvocationInferrer<Node extends AstNodeImpl> {
 
   /// Performs type inference on the invocation expression.
   void resolveInvocation() {
-    var deferredClosures = _visitArguments(rawType: rawType);
+    var deferredClosures = _visitArguments();
     if (deferredClosures != null) {
-      _resolveDeferredClosures(
-          rawType: rawType, deferredClosures: deferredClosures);
+      _resolveDeferredClosures(deferredClosures: deferredClosures);
     }
   }
 
@@ -429,8 +426,7 @@ class InvocationInferrer<Node extends AstNodeImpl> {
 
   /// Resolves any closures that were deferred by [_visitArguments].
   void _resolveDeferredClosures(
-      {required FunctionType? rawType,
-      required Iterable<_DeferredClosure> deferredClosures,
+      {required Iterable<_DeferredClosure> deferredClosures,
       List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo,
       Substitution? substitution,
       GenericInferrer? inferrer}) {
@@ -465,8 +461,7 @@ class InvocationInferrer<Node extends AstNodeImpl> {
   /// be deferred due to the `inference-update-1` feature, a list of them is
   /// returned.
   List<_DeferredClosure>? _visitArguments(
-      {required FunctionType? rawType,
-      List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo,
+      {List<EqualityInfo<PromotableElement, DartType>?>? identicalInfo,
       Substitution? substitution,
       GenericInferrer? inferrer}) {
     assert(whyNotPromotedList.isEmpty);