Decorators normative updates (#55276)

src/compiler/checker.ts

@@ -32875,7 +32875,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
      */
     function getThisArgumentOfCall(node: CallLikeExpression): LeftHandSideExpression | undefined {
         const expression = node.kind === SyntaxKind.CallExpression ? node.expression :
-            node.kind === SyntaxKind.TaggedTemplateExpression ? node.tag : undefined;
+            node.kind === SyntaxKind.TaggedTemplateExpression ? node.tag :
+            node.kind === SyntaxKind.Decorator && !legacyDecorators ? node.expression :
+            undefined;
         if (expression) {
             const callee = skipOuterExpressions(expression);
             if (isAccessExpression(callee)) {

src/compiler/factory/utilities.ts

@@ -1645,7 +1645,7 @@ export function createAccessorPropertyBackingField(factory: NodeFactory, node: P
  *
  * @internal
  */
-export function createAccessorPropertyGetRedirector(factory: NodeFactory, node: PropertyDeclaration, modifiers: ModifiersArray | undefined, name: PropertyName): GetAccessorDeclaration {
+export function createAccessorPropertyGetRedirector(factory: NodeFactory, node: PropertyDeclaration, modifiers: readonly Modifier[] | undefined, name: PropertyName, receiver: Expression = factory.createThis()): GetAccessorDeclaration {
     return factory.createGetAccessorDeclaration(
         modifiers,
         name,
@@ -1654,7 +1654,7 @@ export function createAccessorPropertyGetRedirector(factory: NodeFactory, node:
         factory.createBlock([
             factory.createReturnStatement(
                 factory.createPropertyAccessExpression(
-                    factory.createThis(),
+                    receiver,
                     factory.getGeneratedPrivateNameForNode(node.name, /*prefix*/ undefined, "_accessor_storage")
                 )
             )
@@ -1667,7 +1667,7 @@ export function createAccessorPropertyGetRedirector(factory: NodeFactory, node:
  *
  * @internal
  */
-export function createAccessorPropertySetRedirector(factory: NodeFactory, node: PropertyDeclaration, modifiers: ModifiersArray | undefined, name: PropertyName) {
+export function createAccessorPropertySetRedirector(factory: NodeFactory, node: PropertyDeclaration, modifiers: readonly Modifier[] | undefined, name: PropertyName, receiver: Expression = factory.createThis()) {
     return factory.createSetAccessorDeclaration(
         modifiers,
         name,
@@ -1680,7 +1680,7 @@ export function createAccessorPropertySetRedirector(factory: NodeFactory, node:
             factory.createExpressionStatement(
                 factory.createAssignment(
                     factory.createPropertyAccessExpression(
-                        factory.createThis(),
+                        receiver,
                         factory.getGeneratedPrivateNameForNode(node.name, /*prefix*/ undefined, "_accessor_storage")
                     ),
                     factory.createIdentifier("value")

src/compiler/transformers/classFields.ts

@@ -154,6 +154,7 @@ import {
     Modifier,
     ModifierFlags,
     ModifierLike,
+    modifiersToFlags,
     moveRangePastModifiers,
     moveRangePos,
     newPrivateEnvironment,
@@ -896,6 +897,12 @@ export function transformClassFields(context: TransformationContext): (x: Source
         }
     }
 
+    function getClassThis() {
+        const lex = getClassLexicalEnvironment();
+        const classThis = lex.classThis ?? lex.classConstructor ?? currentClassContainer?.name;
+        return Debug.checkDefined(classThis);
+    }
+
     function transformAutoAccessor(node: AutoAccessorPropertyDeclaration): VisitResult<Node> {
         // transforms:
         //      accessor x = 1;
@@ -935,12 +942,15 @@ export function transformClassFields(context: TransformationContext): (x: Source
         setEmitFlags(backingField, EmitFlags.NoComments);
         setSourceMapRange(backingField, sourceMapRange);
 
-        const getter = createAccessorPropertyGetRedirector(factory, node, modifiers, getterName);
+        const receiver = isStatic(node) ? getClassThis() : factory.createThis();
+        const getter = createAccessorPropertyGetRedirector(factory, node, modifiers, getterName, receiver);
         setOriginalNode(getter, node);
         setCommentRange(getter, commentRange);
         setSourceMapRange(getter, sourceMapRange);
 
-        const setter = createAccessorPropertySetRedirector(factory, node, modifiers, setterName);
+        // create a fresh copy of the modifiers so that we don't duplicate comments
+        const setterModifiers = factory.createModifiersFromModifierFlags(modifiersToFlags(modifiers));
+        const setter = createAccessorPropertySetRedirector(factory, node, setterModifiers, setterName, receiver);
         setOriginalNode(setter, node);
         setEmitFlags(setter, EmitFlags.NoComments);
         setSourceMapRange(setter, sourceMapRange);
@@ -1692,11 +1702,13 @@ export function transformClassFields(context: TransformationContext): (x: Source
         let containsInstanceAutoAccessors = false;
         for (const member of node.members) {
             if (isStatic(member)) {
-                if (member.name &&
-                    (isPrivateIdentifier(member.name) || isAutoAccessorPropertyDeclaration(member)) &&
+                if (member.name && (isPrivateIdentifier(member.name) || isAutoAccessorPropertyDeclaration(member)) &&
                     shouldTransformPrivateElementsOrClassStaticBlocks) {
                     facts |= ClassFacts.NeedsClassConstructorReference;
                 }
+                else if (isAutoAccessorPropertyDeclaration(member) && shouldTransformAutoAccessors === Ternary.True && !node.name && !node.emitNode?.classThis) {
+                    facts |= ClassFacts.NeedsClassConstructorReference;
+                }
                 if (isPropertyDeclaration(member) || isClassStaticBlockDeclaration(member)) {
                     if (shouldTransformThisInStaticInitializers && member.transformFlags & TransformFlags.ContainsLexicalThis) {
                         facts |= ClassFacts.NeedsSubstitutionForThisInClassStaticField;
@@ -1846,10 +1858,10 @@ export function transformClassFields(context: TransformationContext): (x: Source
                 getClassLexicalEnvironment().classConstructor = factory.cloneNode(temp);
                 pendingClassReferenceAssignment = factory.createAssignment(temp, factory.getInternalName(node));
             }
+        }
 
-            if (node.emitNode?.classThis) {
-                getClassLexicalEnvironment().classThis = node.emitNode.classThis;
-            }
+        if (node.emitNode?.classThis) {
+            getClassLexicalEnvironment().classThis = node.emitNode.classThis;
         }
 
         const isClassWithConstructorReference = resolver.getNodeCheckFlags(node) & NodeCheckFlags.ContainsConstructorReference;

src/compiler/transformers/esDecorators.ts

@@ -47,6 +47,7 @@ import {
     getAllDecoratorsOfClassElement,
     getCommentRange,
     getEffectiveBaseTypeNode,
+    getEmitScriptTarget,
     getFirstConstructorWithBody,
     getHeritageClause,
     getNonAssignmentOperatorForCompoundAssignment,
@@ -62,6 +63,7 @@ import {
     injectClassNamedEvaluationHelperBlockIfMissing,
     injectClassThisAssignmentIfMissing,
     InternalEmitFlags,
+    isAccessExpression,
     isAmbientPropertyDeclaration,
     isArrayBindingOrAssignmentElement,
     isArrayLiteralExpression,
@@ -289,6 +291,7 @@ export function transformESDecorators(context: TransformationContext): (x: Sourc
         hoistVariableDeclaration,
     } = context;
 
+    const languageVersion = getEmitScriptTarget(context.getCompilerOptions());
     let top: LexicalEnvironmentStackEntry | undefined;
     let classInfo: ClassInfo | undefined;
     let classThis: Identifier | undefined;
@@ -2147,6 +2150,13 @@ export function transformESDecorators(context: TransformationContext): (x: Sourc
     function transformDecorator(decorator: Decorator) {
         const expression = visitNode(decorator.expression, visitor, isExpression);
         setEmitFlags(expression, EmitFlags.NoComments);
+
+        // preserve the 'this' binding for an access expression
+        const innerExpression = skipOuterExpressions(expression);
+        if (isAccessExpression(innerExpression)) {
+            const { target, thisArg } = factory.createCallBinding(expression, hoistVariableDeclaration, languageVersion, /*cacheIdentifiers*/ true);
+            return factory.restoreOuterExpressions(expression, factory.createFunctionBindCall(target, thisArg, []));
+        }
         return expression;
     }