Deprecate all diagnostics methods that use strings.

pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart

Index: pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart b/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
index 2ff2ecb992a6a80c65139ff008a2e1dd18918e50..a523c19f3e616405d144b33c484c27c35148e1bd 100644
--- a/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
@@ -30,7 +30,7 @@ import 'package:kernel/ast.dart' hide MethodInvocation, InvalidExpression;
 
 import '../names.dart' show equalsName, indexGetName, indexSetName;
 
-import '../errors.dart' show internalError;
+import '../deprecated_problems.dart' show deprecated_internalProblem;
 
 /// An [Accessor] represents a subexpression for which we can't yet build a
 /// kernel [Expression] because we don't yet know the context in which it is
@@ -176,7 +176,7 @@ abstract class Accessor {
   ///
   /// At runtime, an exception will be thrown.
   makeInvalidRead() {
-    return internalError(
+    return deprecated_internalProblem(
         "Unhandled compile-time error.", null, offsetForToken(token));
   }
 
@@ -185,7 +185,7 @@ abstract class Accessor {
   ///
   /// At runtime, [value] will be evaluated before throwing an exception.
   makeInvalidWrite(Expression value) {
-    return internalError(
+    return deprecated_internalProblem(
         "Unhandled compile-time error.", null, offsetForToken(token));
   }