[analyzer][cfe] Introduce parsing for null-aware elements

Part of #55949 Closes #55954 Change-Id: I885772f292f6d70425d6eba15bad8b0c6dc86a1f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/370240 Reviewed-by: Keerti Parthasarathy <[email protected]> Commit-Queue: Chloe Stefantsova <[email protected]> Reviewed-by: Johnni Winther <[email protected]>
dart-lang · Jun 28, 2024 · a4c9471 · a4c9471
1 parent 4a8b3c7
commit a4c9471
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Showing 61 changed files with 2,561 additions and 86 deletions.
diff --git a/pkg/_fe_analyzer_shared/lib/src/parser/forwarding_listener.dart b/pkg/_fe_analyzer_shared/lib/src/parser/forwarding_listener.dart
@@ -1649,8 +1649,11 @@ class ForwardingListener implements Listener {
   }
 
   @override
-  void handleLiteralMapEntry(Token colon, Token endToken) {
-    listener?.handleLiteralMapEntry(colon, endToken);
+  void handleLiteralMapEntry(Token colon, Token endToken,
+      {Token? nullAwareKeyToken, Token? nullAwareValueToken}) {
+    listener?.handleLiteralMapEntry(colon, endToken,
+        nullAwareKeyToken: nullAwareKeyToken,
+        nullAwareValueToken: nullAwareValueToken);
   }
 
   @override
@@ -1909,6 +1912,11 @@ class ForwardingListener implements Listener {
     listener?.endConstantPattern(constKeyword);
   }
 
+  @override
+  void handleNullAwareElement(Token nullAwareToken) {
+    listener?.handleNullAwareElement(nullAwareToken);
+  }
+
   @override
   void handleObjectPattern(
       Token firstIdentifier, Token? dot, Token? secondIdentifier) {

diff --git a/pkg/_fe_analyzer_shared/lib/src/parser/listener.dart b/pkg/_fe_analyzer_shared/lib/src/parser/listener.dart
@@ -1113,8 +1113,14 @@ class Listener implements UnescapeErrorListener {
     logEvent("LibraryName");
   }
 
+  /// Called after parsing a map entry. Either the key or the value or both can
+  /// start with the null-aware token `?`. In that case, [nullAwareKeyToken] and
+  /// [nullAwareValueToken] are set appropriately. Substructures:
+  /// - expression
+  /// - expression
   // TODO(jensj): Should this have a `beginToken`?
-  void handleLiteralMapEntry(Token colon, Token endToken) {
+  void handleLiteralMapEntry(Token colon, Token endToken,
+      {Token? nullAwareKeyToken, Token? nullAwareValueToken}) {
     logEvent("LiteralMapEntry");
   }
 
@@ -1882,6 +1888,13 @@ class Listener implements UnescapeErrorListener {
     logEvent("SpreadExpression");
   }
 
+  /// Called after parsing a list or set element that starts with the null-aware
+  /// token `?`. Substructures:
+  /// - expression
+  void handleNullAwareElement(Token nullAwareToken) {
+    logEvent("NullAwareElement");
+  }
+
   /// Called after parsing an element of a list or map pattern that starts with
   /// `...`.  Substructures:
   /// - pattern (if hasSubPattern is `true`)

diff --git a/pkg/_fe_analyzer_shared/lib/src/parser/literal_entry_info.dart b/pkg/_fe_analyzer_shared/lib/src/parser/literal_entry_info.dart
@@ -63,6 +63,8 @@ LiteralEntryInfo computeLiteralEntry(Token token) {
     return new ForCondition();
   } else if (optional('...', next) || optional('...?', next)) {
     return spreadOperator;
+  } else if (optional('?', next)) {
+    return nullAwareEntry;
   }
   return simpleEntry;
 }

diff --git a/pkg/_fe_analyzer_shared/lib/src/parser/literal_entry_info_impl.dart b/pkg/_fe_analyzer_shared/lib/src/parser/literal_entry_info_impl.dart
@@ -15,6 +15,12 @@ const LiteralEntryInfo ifCondition = const IfCondition();
 /// preceded by a '...' spread operator.
 const LiteralEntryInfo spreadOperator = const SpreadOperator();
 
+/// [nullAwareEntry] is for parsing a null-aware element in a literal list or
+/// set, preceded by the `?` null-aware marker, or a null-aware map entry in a
+/// map literal, where either the key or the value is preceded by the `?`
+/// null-aware marker.
+const NullAwareEntry nullAwareEntry = const NullAwareEntry();
+
 /// The first step when processing a `for` control flow collection entry.
 class ForCondition extends LiteralEntryInfo {
   bool _inStyle = false;
@@ -86,6 +92,9 @@ class ForCondition extends LiteralEntryInfo {
       );
     } else if (optional('...', next) || optional('...?', next)) {
       return _inStyle ? const ForInSpread() : const ForSpread();
+    } else if (optional('?', next)) {
+      return new Nested(nullAwareEntry,
+          _inStyle ? const ForInComplete() : const ForComplete());
     }
     return _inStyle ? const ForInEntry() : const ForEntry();
   }
@@ -180,6 +189,8 @@ class IfCondition extends LiteralEntryInfo {
       return new Nested(ifCondition, const IfComplete());
     } else if (optional('...', next) || optional('...?', next)) {
       return const IfSpread();
+    } else if (optional('?', next)) {
+      return new Nested(nullAwareEntry, const IfComplete());
     }
     return const IfEntry();
   }
@@ -308,3 +319,30 @@ class Nested extends LiteralEntryInfo {
     return nestedStep != null ? this : lastStep;
   }
 }
+
+class NullAwareEntry extends LiteralEntryInfo {
+  const NullAwareEntry() : super(false, 0);
+
+  @override
+  Token parse(Token token, Parser parser) {
+    final Token entryNullAwareToken = token.next!;
+    assert(optional('?', entryNullAwareToken));
+    token = parser.parseExpression(entryNullAwareToken);
+    if (optional(':', token.next!)) {
+      Token colon = token.next!;
+      Token next = colon.next!;
+      if (optional('?', next)) {
+        token = parser.parseExpression(next);
+        parser.listener.handleLiteralMapEntry(colon, token,
+            nullAwareKeyToken: entryNullAwareToken, nullAwareValueToken: next);
+      } else {
+        token = parser.parseExpression(colon);
+        parser.listener.handleLiteralMapEntry(colon, token,
+            nullAwareKeyToken: entryNullAwareToken, nullAwareValueToken: null);
+      }
+    } else {
+      parser.listener.handleNullAwareElement(entryNullAwareToken);
+    }
+    return token;
+  }
+}
diff --git a/pkg/_fe_analyzer_shared/lib/src/parser/parser_impl.dart b/pkg/_fe_analyzer_shared/lib/src/parser/parser_impl.dart
@@ -6991,17 +6991,39 @@ class Parser {
         hasSetEntry ??= !isMapEntry;
         if (isMapEntry) {
           Token colon = token.next!;
-          token = parseExpression(colon);
-          listener.handleLiteralMapEntry(colon, token.next!);
+          Token next = colon.next!;
+          if (optional('?', next)) {
+            // Null-aware value. For example:
+            //   <int, String>{ x: ?y }
+            token = parseExpression(next);
+            listener.handleLiteralMapEntry(colon, token,
+                nullAwareKeyToken: null, nullAwareValueToken: next);
+          } else {
+            // Non null-aware entry. For example:
+            //   <bool, num>{ x: y }
+            token = parseExpression(colon);
+            listener.handleLiteralMapEntry(colon, token.next!);
+          }
         }
       } else {
         while (info != null) {
           if (info.hasEntry) {
             token = parseExpression(token);
             if (optional(':', token.next!)) {
               Token colon = token.next!;
-              token = parseExpression(colon);
-              listener.handleLiteralMapEntry(colon, token.next!);
+              Token next = colon.next!;
+              if (optional('?', next)) {
+                token = parseExpression(next);
+                // Null-aware value. For example:
+                //   <double, Symbol>{ if (b) x: ?y }
+                listener.handleLiteralMapEntry(colon, token,
+                    nullAwareKeyToken: null, nullAwareValueToken: next);
+              } else {
+                // Non null-aware entry. For example:
+                //   <String, int>{ if (b) x : y }
+                token = parseExpression(colon);
+                listener.handleLiteralMapEntry(colon, token.next!);
+              }
             }
           } else {
             token = info.parse(token, this);

diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -147,6 +147,9 @@ class AstBuilder extends StackListener {
   /// `true` if class-modifiers is enabled
   final bool enableClassModifiers;
 
+  /// `true` if null-aware elements is enabled
+  final bool enableNullAwareElements;
+
   final FeatureSet _featureSet;
 
   final LineInfo _lineInfo;
@@ -174,6 +177,8 @@ class AstBuilder extends StackListener {
         enableInlineClass = _featureSet.isEnabled(Feature.inline_class),
         enableSealedClass = _featureSet.isEnabled(Feature.sealed_class),
         enableClassModifiers = _featureSet.isEnabled(Feature.class_modifiers),
+        enableNullAwareElements =
+            _featureSet.isEnabled(Feature.null_aware_elements),
         uri = uri ?? fileUri;
 
   @override
@@ -4746,10 +4751,20 @@ class AstBuilder extends StackListener {
   }
 
   @override
-  void handleLiteralMapEntry(Token colon, Token endToken) {
+  void handleLiteralMapEntry(Token colon, Token endToken,
+      {Token? nullAwareKeyToken, Token? nullAwareValueToken}) {
     assert(optional(':', colon));
     debugEvent("LiteralMapEntry");
 
+    // TODO(cstefantsova): Handle null-aware map entries.
+    if (!enableNullAwareElements &&
+        (nullAwareKeyToken != null || nullAwareValueToken != null)) {
+      _reportFeatureNotEnabled(
+        feature: ExperimentalFeatures.null_aware_elements,
+        startToken: nullAwareKeyToken ?? nullAwareValueToken!,
+      );
+    }
+
     var value = pop() as ExpressionImpl;
     var key = pop() as ExpressionImpl;
     push(
@@ -5036,6 +5051,18 @@ class AstBuilder extends StackListener {
     );
   }
 
+  @override
+  void handleNullAwareElement(Token nullAwareElement) {
+    debugEvent('NullAwareElement');
+    // TODO(cstefantsova): Handle null-aware elements.
+    if (!enableNullAwareElements) {
+      _reportFeatureNotEnabled(
+        feature: ExperimentalFeatures.null_aware_elements,
+        startToken: nullAwareElement,
+      );
+    }
+  }
+
   @override
   void handleNullCheckPattern(Token question) {
     debugEvent('NullCheckPattern');

diff --git a/pkg/front_end/lib/src/kernel/body_builder.dart b/pkg/front_end/lib/src/kernel/body_builder.dart
@@ -4995,11 +4995,29 @@ class BodyBuilder extends StackListenerImpl
   }
 
   @override
-  void handleLiteralMapEntry(Token colon, Token endToken) {
+  void handleLiteralMapEntry(Token colon, Token endToken,
+      {Token? nullAwareKeyToken, Token? nullAwareValueToken}) {
     debugEvent("LiteralMapEntry");
     Expression value = popForValue();
     Expression key = popForValue();
-    push(forest.createMapEntry(offsetForToken(colon), key, value));
+    if (nullAwareKeyToken == null && nullAwareValueToken == null) {
+      push(forest.createMapEntry(offsetForToken(colon), key, value));
+    } else {
+      if (!libraryFeatures.nullAwareElements.isEnabled) {
+        addProblem(
+            templateExperimentNotEnabledOffByDefault
+                .withArguments(ExperimentalFlag.nullAwareElements.name),
+            (nullAwareKeyToken ?? nullAwareValueToken!).offset,
+            noLength);
+      }
+      // TODO(cstefantsova): Replace the following no-op with the node for
+      // handling null-aware elements.
+      push(forest.createSpreadElement(
+          offsetForToken(nullAwareKeyToken ?? nullAwareValueToken!),
+          forest.createNullLiteral(
+              offsetForToken(nullAwareKeyToken ?? nullAwareValueToken!)),
+          isNullAware: true));
+    }
   }
 
   String symbolPartToString(name) {
@@ -7129,6 +7147,24 @@ class BodyBuilder extends StackListenerImpl
     typeInferrer.assignedVariables.storeInfo(node, assignedVariablesInfo);
   }
 
+  @override
+  void handleNullAwareElement(Token nullAwareElement) {
+    debugEvent("NullAwareElement");
+    // TODO(cstefantsova): Replace the following no-op with the node for
+    // handling null-aware elements.
+    if (!libraryFeatures.nullAwareElements.isEnabled) {
+      addProblem(
+          templateExperimentNotEnabledOffByDefault
+              .withArguments(ExperimentalFlag.nullAwareElements.name),
+          nullAwareElement.offset,
+          noLength);
+    }
+    pop(); // Expression.
+    push(forest.createSpreadElement(offsetForToken(nullAwareElement),
+        forest.createNullLiteral(offsetForToken(nullAwareElement)),
+        isNullAware: true));
+  }
+
   @override
   void handleSpreadExpression(Token spreadToken) {
     debugEvent("SpreadExpression");

diff --git a/pkg/front_end/lib/src/kernel/macro/annotation_parser.dart b/pkg/front_end/lib/src/kernel/macro/annotation_parser.dart
@@ -1967,7 +1967,8 @@ class _MacroListener implements Listener {
   }
 
   @override
-  void handleLiteralMapEntry(Token colon, Token endToken) {
+  void handleLiteralMapEntry(Token colon, Token endToken,
+      {Token? nullAwareKeyToken, Token? nullAwareValueToken}) {
     _unhandled('map entry');
   }
 
@@ -2188,6 +2189,11 @@ class _MacroListener implements Listener {
     _unsupported();
   }
 
+  @override
+  void handleNullAwareElement(Token spreadToken) {
+    _unsupported();
+  }
+
   @override
   void handleObjectPattern(
       Token firstIdentifier, Token? dot, Token? secondIdentifier) {