[analyzer] Allow spreads between const lists and sets in the const evaluator

The change allows const lists to be in the spread of a const set and vice-versa. It also reports the correct error if we use a map in a list/set (and vice-versa) which is necessary when we combine all the error reporting in the `ConstantVisitor` to one location.

Adds some additional tests to make sure the behaviour we want is still working.

Change-Id: I0f64d58c857bd905ac8521346cd34a113b6d4a40
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/323780
Commit-Queue: Kallen Tu <kallentu@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

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

@@ -605,6 +605,10 @@ class ConstantVerifier extends RecursiveAstVisitor<void> {
           identical(dataErrorCode,
               CompileTimeErrorCode.CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH) ||
           identical(dataErrorCode, CompileTimeErrorCode.CONST_TYPE_PARAMETER) ||
+          identical(
+              dataErrorCode, CompileTimeErrorCode.CONST_SPREAD_EXPECTED_MAP) ||
+          identical(dataErrorCode,
+              CompileTimeErrorCode.CONST_SPREAD_EXPECTED_LIST_OR_SET) ||
           identical(
               dataErrorCode,
               CompileTimeErrorCode

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

@@ -1264,6 +1264,17 @@ class ConstantVisitor extends UnifyingAstVisitor<Constant> {
       for (CollectionElement element in node.elements) {
         var result = _addElementsToMap(map, element);
         if (result is InvalidConstant) {
+          if (result.errorCode ==
+                  CompileTimeErrorCode.CONST_SPREAD_EXPECTED_MAP &&
+              node.isMap) {
+            // Only report the error if we know this is a non-ambiguous map.
+            // TODO(kallentu): Don't report error here and avoid reporting this
+            // error in this case.
+            _errorReporter.reportErrorForOffset(
+                CompileTimeErrorCode.CONST_SPREAD_EXPECTED_MAP,
+                result.entity.offset,
+                result.entity.length);
+          }
           return result;
         }
       }
@@ -1404,8 +1415,16 @@ class ConstantVisitor extends UnifyingAstVisitor<Constant> {
           case InvalidConstant():
             return spread;
           case DartObjectImpl():
-            var listValue = spread.toListValue();
+            // Special case for ...?
+            if (spread.isNull && element.isNullAware) {
+              return null;
+            }
+            var listValue = spread.toListValue() ?? spread.toSetValue();
             if (listValue == null) {
+              // TODO(kallentu): Don't report error here.
+              _errorReporter.reportErrorForNode(
+                  CompileTimeErrorCode.CONST_SPREAD_EXPECTED_LIST_OR_SET,
+                  element.expression);
               return InvalidConstant(element.expression,
                   CompileTimeErrorCode.CONST_SPREAD_EXPECTED_LIST_OR_SET);
             }
@@ -1471,6 +1490,10 @@ class ConstantVisitor extends UnifyingAstVisitor<Constant> {
           case InvalidConstant():
             return spread;
           case DartObjectImpl():
+            // Special case for ...?
+            if (spread.isNull && element.isNullAware) {
+              return null;
+            }
             var mapValue = spread.toMapValue();
             if (mapValue == null) {
               return InvalidConstant(element.expression,
@@ -1533,8 +1556,16 @@ class ConstantVisitor extends UnifyingAstVisitor<Constant> {
           case InvalidConstant():
             return spread;
           case DartObjectImpl():
-            var setValue = spread.toSetValue();
+            // Special case for ...?
+            if (spread.isNull && element.isNullAware) {
+              return null;
+            }
+            var setValue = spread.toSetValue() ?? spread.toListValue();
             if (setValue == null) {
+              // TODO(kallentu): Don't report error here.
+              _errorReporter.reportErrorForNode(
+                  CompileTimeErrorCode.CONST_SPREAD_EXPECTED_LIST_OR_SET,
+                  element.expression);
               return InvalidConstant(element.expression,
                   CompileTimeErrorCode.CONST_SPREAD_EXPECTED_LIST_OR_SET);
             }

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

@@ -2050,6 +2050,43 @@ const x = <int>[...a];
     _assertNull(result);
   }
 
+  test_visitListLiteral_spreadElement_null() async {
+    await assertNoErrorsInCode('''
+const a = null;
+const List<String> x = [
+  'anotherString',
+  ...?a,
+];
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+List
+  elementType: String
+  elements
+    String anotherString
+  variable: self::@variable::x
+''');
+  }
+
+  test_visitListLiteral_spreadElement_set() async {
+    await assertNoErrorsInCode('''
+const a = {'string'};
+const List<String> x = [
+  'anotherString',
+  ...a,
+];
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+List
+  elementType: String
+  elements
+    String anotherString
+    String string
+  variable: self::@variable::x
+''');
+  }
+
   test_visitMethodInvocation_notIdentical() async {
     await assertErrorsInCode(r'''
 int f() {
@@ -2373,6 +2410,34 @@ Record(int, String, {bool c})
 ''');
   }
 
+  test_visitSetOrMapLiteral_ambiguous() async {
+    await assertErrorsInCode(r'''
+const l = [];
+const ambiguous = {...l, 1: 2};
+''', [
+      error(CompileTimeErrorCode.AMBIGUOUS_SET_OR_MAP_LITERAL_BOTH, 32, 12),
+    ]);
+  }
+
+  test_visitSetOrMapLiteral_ambiguous_either() async {
+    await assertErrorsInCode(r'''
+const int? i = 1;
+const res  = {...?i};
+''', [
+      error(CompileTimeErrorCode.AMBIGUOUS_SET_OR_MAP_LITERAL_EITHER, 31, 7),
+    ]);
+  }
+
+  test_visitSetOrMapLiteral_ambiguous_inList() async {
+    await assertErrorsInCode(r'''
+const l = [];
+const ambiguous = {...l, 1: 2};
+const anotherList = [...ambiguous];
+''', [
+      error(CompileTimeErrorCode.AMBIGUOUS_SET_OR_MAP_LITERAL_BOTH, 32, 12),
+    ]);
+  }
+
   test_visitSetOrMapLiteral_map_complexKey() async {
     await assertNoErrorsInCode(r'''
 class A {
@@ -2454,6 +2519,57 @@ Map
 ''');
   }
 
+  test_visitSetOrMapLiteral_map_spread() async {
+    await assertNoErrorsInCode('''
+const x = {'string': 1};
+const Map<String, int> alwaysInclude = {
+  'anotherString': 0,
+  ...x,
+};
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+Map
+  entries
+    entry
+      key: String string
+      value: int 1
+  variable: self::@variable::x
+''');
+  }
+
+  test_visitSetOrMapLiteral_map_spread_notMap() async {
+    await assertErrorsInCode('''
+const x = ['string'];
+const Map<String, int> alwaysInclude = {
+  'anotherString': 0,
+  ...x,
+};
+''', [
+      error(CompileTimeErrorCode.CONST_SPREAD_EXPECTED_MAP, 90, 1),
+      error(CompileTimeErrorCode.NOT_MAP_SPREAD, 90, 1),
+    ]);
+  }
+
+  test_visitSetOrMapLiteral_map_spread_null() async {
+    await assertNoErrorsInCode('''
+const a = null;
+const Map<String, int> x = {
+  'anotherString': 0,
+  ...?a,
+};
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+Map
+  entries
+    entry
+      key: String anotherString
+      value: int 0
+  variable: self::@variable::x
+''');
+  }
+
   test_visitSetOrMapLiteral_set_double_zeros() async {
     await assertNoErrorsInCode(r'''
 class C {
@@ -2504,6 +2620,41 @@ const c = const {if (nonBool) 3};
     _assertNull(result);
   }
 
+  test_visitSetOrMapLiteral_set_spread_list() async {
+    await assertNoErrorsInCode('''
+const a = ['string'];
+const Set<String> x = {
+  'anotherString',
+  ...a,
+};
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+Set
+  elements
+    String anotherString
+    String string
+  variable: self::@variable::x
+''');
+  }
+
+  test_visitSetOrMapLiteral_set_spread_null() async {
+    await assertNoErrorsInCode('''
+const a = null;
+const Set<String> x = {
+  'anotherString',
+  ...?a,
+};
+''');
+    final result = _topLevelVar('x');
+    assertDartObjectText(result, '''
+Set
+  elements
+    String anotherString
+  variable: self::@variable::x
+''');
+  }
+
   test_visitSimpleIdentifier_className() async {
     await assertNoErrorsInCode('''
 const a = C;