Partial implementation of record types in DartEditBuilder

While the work is incomplete (see the TODOs), this fixes an exception
that I saw this morning and is, I believe, a step in the right direction.

Change-Id: I6adc0e0df4ea9b64ea0c5d1dcd42a078d30c4a9b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/258507
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: bwilkerson

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart

@@ -906,6 +906,12 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
       return true;
     }
 
+    if (type is RecordType) {
+      // TODO(brianwilkerson) This should return `false` if the `records`
+      //  feature is not enabled.
+      return true;
+    }
+
     throw UnimplementedError('(${type.runtimeType}) $type');
   }
 
@@ -1279,6 +1285,50 @@ class DartEditBuilderImpl extends EditBuilderImpl implements DartEditBuilder {
       return true;
     }
 
+    if (type is RecordType) {
+      // TODO(brianwilkerson) This should return `false` if the `records`
+      //  feature is not enabled. More importantly, we can't currently return
+      //  `false` if some portion of a type has already been written, so we
+      //  need to figure out what to do when a record type is nested in another
+      //  type in a context where it isn't allowed. For example, we might
+      //  enhance `_canWriteType` to be recursive, then guard all invocations of
+      //  this method with a call to `_canWriteType` (and remove the return type
+      //  from this method).
+      write('(');
+      var isFirst = true;
+      for (var field in type.positionalFields) {
+        if (isFirst) {
+          isFirst = false;
+        } else {
+          write(', ');
+        }
+        _writeType(field.type);
+      }
+      var namedFields = type.namedFields;
+      if (namedFields.isNotEmpty) {
+        if (isFirst) {
+          write('{');
+        } else {
+          write(', {');
+        }
+        isFirst = true;
+        for (var field in namedFields) {
+          if (isFirst) {
+            isFirst = false;
+          } else {
+            write(', ');
+          }
+          _writeType(field.type);
+          write(' ');
+          write(field.name);
+        }
+        write('}');
+      }
+      write(')');
+      _writeTypeNullability(type);
+      return true;
+    }
+
     throw UnimplementedError('(${type.runtimeType}) $type');
   }
 

pkg/analyzer_plugin/test/src/utilities/change_builder/change_builder_dart_test.dart

@@ -61,6 +61,22 @@ class DartEditBuilderImpl_WithNullSafetyTest extends DartEditBuilderImplTest {
   Future<void> test_writeType_Never_question() async {
     await _assertWriteType('Never?');
   }
+
+  Future<void> test_writeType_recordType_mixed() async {
+    await _assertWriteType('(int, {int y})');
+  }
+
+  Future<void> test_writeType_recordType_named() async {
+    await _assertWriteType('({int x, int y})');
+  }
+
+  Future<void> test_writeType_recordType_nullable() async {
+    await _assertWriteType('(int, {int y})?');
+  }
+
+  Future<void> test_writeType_recordType_positional() async {
+    await _assertWriteType('(int, int)');
+  }
 }
 
 @reflectiveTest