In the new task model, use explicit dependencies on the type provider.

pkg/analyzer/lib/src/context/context.dart

Index: pkg/analyzer/lib/src/context/context.dart
diff --git a/pkg/analyzer/lib/src/context/context.dart b/pkg/analyzer/lib/src/context/context.dart
index c0f60ffa5f560a46e06dac4322dbe1a5e565e193..bc3d62f01d6606cfba56f95d21ac85d83c1a9610 100644
--- a/pkg/analyzer/lib/src/context/context.dart
+++ b/pkg/analyzer/lib/src/context/context.dart
@@ -420,6 +420,10 @@ class AnalysisContextImpl implements InternalAnalysisContext {
 
   @override
   TypeProvider get typeProvider {
+    // Make sure a task didn't accidentally try to call back into the context
+    // to retrieve the type provider.
+    assert(!driver.isTaskRunning);
+
     if (_typeProvider != null) {
       return _typeProvider;
     }