Re-write of the computation of the context type for code completion. Instead of passing a parent and child node, a parent node with an offset is passed. The primary purpose of this change was to fix a bug with argument lists which is close to being fixed.

I will follow up with some additional fixes and tests for map and list literals.

Change-Id: I1a26e8f900dcf13402385a49e8f3538c5d1b39df
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151030
Commit-Queue: Jaime Wren <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: jwren

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

@@ -429,9 +429,8 @@ class DartCompletionRequestImpl implements DartCompletionRequest {
   DartType get contextType {
     if (!_hasComputedContextType) {
       var entity = target.entity;
-      if (entity is AstNode) {
-        _contextType = featureComputer.computeContextType(entity);
-      }
+      _contextType = featureComputer.computeContextType(
+          target.containingNode, entity.offset);
       _hasComputedContextType = true;
     }
     return _contextType;