refactor duplicate code into single visitor

pkg/analysis_server/lib/src/services/completion/invocation_computer.dart

Index: pkg/analysis_server/lib/src/services/completion/invocation_computer.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/invocation_computer.dart b/pkg/analysis_server/lib/src/services/completion/invocation_computer.dart
index e2a229bdbd5caace1b9f335ef901f6adf921c885..b7d2c64e49524989e84c3e3e683e32c898d1eda6 100644
--- a/pkg/analysis_server/lib/src/services/completion/invocation_computer.dart
+++ b/pkg/analysis_server/lib/src/services/completion/invocation_computer.dart
@@ -7,6 +7,7 @@ library services.completion.computer.dart.invocation;
 import 'dart:async';
 
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
+import 'package:analysis_server/src/services/completion/optype_ast_visitor.dart';
 import 'package:analysis_server/src/services/completion/suggestion_builder.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ -23,10 +24,19 @@ class InvocationComputer extends DartCompletionComputer {
 
   @override
   bool computeFast(DartCompletionRequest request) {
-    builder = request.node.accept(new _InvocationAstVisitor(request));
-    if (builder != null) {
-      return builder.computeFast(request.node);
+
+    // Determine the type of suggestions to be made
+    OpTypeAstVisitor opTypeVisitor = new OpTypeAstVisitor(request.offset);
+    request.node.accept(opTypeVisitor);
+
+    // Build the suggestions
+    if (opTypeVisitor.includeInvocationSuggestions) {
+      builder = request.node.accept(new _InvocationAstVisitor(request));
+      if (builder != null) {
+        return builder.computeFast(request.node);
+      }
     }
+
     return true;
   }
 
@@ -83,26 +93,12 @@ class _InvocationAstVisitor extends GeneralizingAstVisitor<SuggestionBuilder> {
   visitConstructorName(ConstructorName node) {
     // some PrefixedIdentifier nodes are transformed into
     // ConstructorName nodes during the resolution process.
-    Token period = node.period;
-    if (period != null && request.offset > period.offset) {
-      TypeName type = node.type;
-      if (type != null) {
-        SimpleIdentifier prefix = type.name;
-        if (prefix != null) {
-          return new _PrefixedIdentifierSuggestionBuilder(request);
-        }
-      }
-    }
-    return null;
+    return new _PrefixedIdentifierSuggestionBuilder(request);
   }
 
   @override
   SuggestionBuilder visitMethodInvocation(MethodInvocation node) {
-    Token period = node.period;
-    if (period == null || period.offset < request.offset) {
-      return new _ExpressionSuggestionBuilder(request);
-    }
-    return null;
+    return new _ExpressionSuggestionBuilder(request);
   }
 
   @override
@@ -114,23 +110,12 @@ class _InvocationAstVisitor extends GeneralizingAstVisitor<SuggestionBuilder> {
   SuggestionBuilder visitPrefixedIdentifier(PrefixedIdentifier node) {
     // some PrefixedIdentifier nodes are transformed into
     // ConstructorName nodes during the resolution process.
-    Token period = node.period;
-    if (period != null && request.offset > period.offset) {
-      SimpleIdentifier prefix = node.prefix;
-      if (prefix != null) {
-        return new _PrefixedIdentifierSuggestionBuilder(request);
-      }
-    }
-    return null;
+    return new _PrefixedIdentifierSuggestionBuilder(request);
   }
 
   @override
   SuggestionBuilder visitPropertyAccess(PropertyAccess node) {
-    Token operator = node.operator;
-    if (operator != null && operator.offset < request.offset) {
-      return new _ExpressionSuggestionBuilder(request);
-    }
-    return null;
+    return new _ExpressionSuggestionBuilder(request);
   }
 
   @override