[analyzer] Add DartObject.toRecordValue()

The `DartObject` class in the analyzer represents a known constant
value. It has methods that convert that representation into a more
specific one (e.g. `toListValue()` that returns a list of
`DartObject`).

While constant records can be represented as `DartObject`, there's no
method to directly extract the positional and named fields from that
instance. Users could extract the shape from the record type and then
call `getField`, but that is an error-prone process.
So, this adds `toRecordValue()`, which returns a list for positional
and a map for named parameters when called on a `DartObject`
representing a record.

TEST=pkg/analyzer/test/src/dart/constant/value_test.dart

Change-Id: I56f3e877ea78ab0f3ccfb7ac73ffda80ee4fe846
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/394860
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: simolus3

pkg/analyzer/lib/dart/constant/value.dart

@@ -121,6 +121,14 @@ abstract class DartObject {
   /// * the value of the object being represented is `null`.
   Map<DartObject?, DartObject?>? toMapValue();
 
+  /// If this [DartObject] represents a record, returns the positional and named
+  /// fields of that record.
+  ///
+  /// If the object being represented is not a [Record] `null` is returned
+  /// instead.
+  ({List<DartObject> positional, Map<String, DartObject> named})?
+      toRecordValue();
+
   /// Return a set corresponding to the value of the object being represented,
   /// or `null` if
   /// * this object is not of type 'Set', or

pkg/analyzer/lib/src/dart/constant/value.dart

@@ -924,6 +924,16 @@ class DartObjectImpl implements DartObject, Constant {
     return null;
   }
 
+  @override
+  ({List<DartObject> positional, Map<String, DartObject> named})?
+      toRecordValue() {
+    if (state case RecordState(:var positionalFields, :var namedFields)) {
+      return (positional: positionalFields, named: namedFields);
+    } else {
+      return null;
+    }
+  }
+
   @override
   Set<DartObjectImpl>? toSetValue() {
     var state = this.state;

pkg/analyzer/test/src/dart/constant/value_test.dart

@@ -1928,6 +1928,25 @@ class DartObjectImplTest {
     _assertTimes(_intValue(null), _intValue(null), _intValue(3));
   }
 
+  void test_toRecordValue_notARecord() {
+    expect(
+      _listValue(_typeProvider.boolType, [_boolValue(true), _boolValue(false)])
+          .toRecordValue(),
+      isNull,
+    );
+  }
+
+  void test_toRecordValue_null() {
+    expect(_nullValue().toRecordValue(), isNull);
+  }
+
+  void test_toRecordValue_record() {
+    var constant = _recordValue([_intValue(1)], {'bool': _boolValue(true)});
+    var (:positional, :named) = constant.toRecordValue()!;
+    expect(positional, [_intValue(1)]);
+    expect(named, {'bool': _boolValue(true)});
+  }
+
   /// Assert that the result of executing [fn] is the [expected] value, or, if
   /// [expected] is `null`, that the operation throws an exception .
   void _assert(DartObjectImpl? expected, DartObjectImpl? Function() fn) {