Instantiation expressions (#47607)

* Permit type arguments in references to generic functions

* Accept new baselines

* Delete pointless fourslash test

* Fix lint issue

* Finalize implementation

* Add tests

* Accept new baselines

* Properly handle instantiation of instantiation expression types

* Accept new API baselines

* Fix lint error

* Add more tests

* Properly handle unions/intersections of generic types

* Add more tests

* More permissive parsing of type arguments in member expressions

* Update tests

* Accept new baselines

Author: ahejlsberg

src/compiler/checker.ts

@@ -1152,10 +1152,6 @@
         "category": "Error",
         "code": 1383
     },
-    "A 'new' expression with type arguments must always be followed by a parenthesized argument list.": {
-        "category": "Error",
-        "code": 1384
-    },
     "Function type notation must be parenthesized when used in a union type.": {
         "category": "Error",
         "code": 1385
@@ -2703,6 +2699,10 @@
         "category": "Error",
         "code": 2634
     },
+    "Type '{0}' has no signatures for which the type argument list is applicable.": {
+        "category": "Error",
+        "code": 2635
+    },
 
     "Cannot augment module '{0}' with value exports because it resolves to a non-module entity.": {
         "category": "Error",

src/compiler/diagnosticMessages.json

@@ -1727,6 +1727,8 @@ namespace ts {
                         return emitAsExpression(node as AsExpression);
                     case SyntaxKind.NonNullExpression:
                         return emitNonNullExpression(node as NonNullExpression);
+                    case SyntaxKind.ExpressionWithTypeArguments:
+                        return emitExpressionWithTypeArguments(node as ExpressionWithTypeArguments);
                     case SyntaxKind.MetaProperty:
                         return emitMetaProperty(node as MetaProperty);
                     case SyntaxKind.SyntheticExpression:
@@ -2227,6 +2229,7 @@ namespace ts {
             writeKeyword("typeof");
             writeSpace();
             emit(node.exprName);
+            emitTypeArguments(node, node.typeArguments);
         }
 
         function emitTypeLiteral(node: TypeLiteralNode) {

src/compiler/emitter.ts

@@ -1839,17 +1839,19 @@ namespace ts {
         }
 
         // @api
-        function createTypeQueryNode(exprName: EntityName) {
+        function createTypeQueryNode(exprName: EntityName, typeArguments?: readonly TypeNode[]) {
             const node = createBaseNode<TypeQueryNode>(SyntaxKind.TypeQuery);
             node.exprName = exprName;
+            node.typeArguments = typeArguments && parenthesizerRules().parenthesizeTypeArguments(typeArguments);
             node.transformFlags = TransformFlags.ContainsTypeScript;
             return node;
         }
 
         // @api
-        function updateTypeQueryNode(node: TypeQueryNode, exprName: EntityName) {
+        function updateTypeQueryNode(node: TypeQueryNode, exprName: EntityName, typeArguments?: readonly TypeNode[]) {
             return node.exprName !== exprName
-                ? update(createTypeQueryNode(exprName), node)
+                || node.typeArguments !== typeArguments
+                ? update(createTypeQueryNode(exprName, typeArguments), node)
                 : node;
         }
 

src/compiler/factory/nodeFactory.ts

@@ -180,7 +180,8 @@ namespace ts {
                     visitNode(cbNode, (node as TypePredicateNode).parameterName) ||
                     visitNode(cbNode, (node as TypePredicateNode).type);
             case SyntaxKind.TypeQuery:
-                return visitNode(cbNode, (node as TypeQueryNode).exprName);
+                return visitNode(cbNode, (node as TypeQueryNode).exprName) ||
+                    visitNodes(cbNode, cbNodes, (node as TypeQueryNode).typeArguments);
             case SyntaxKind.TypeLiteral:
                 return visitNodes(cbNode, cbNodes, (node as TypeLiteralNode).members);
             case SyntaxKind.ArrayType:
@@ -3078,7 +3079,9 @@ namespace ts {
         function parseTypeQuery(): TypeQueryNode {
             const pos = getNodePos();
             parseExpected(SyntaxKind.TypeOfKeyword);
-            return finishNode(factory.createTypeQueryNode(parseEntityName(/*allowReservedWords*/ true, /*allowPrivateIdentifiers*/ true)), pos);
+            const entityName = parseEntityName(/*allowReservedWords*/ true, /*allowPrivateIdentifiers*/ true);
+            const typeArguments = tryParseTypeArguments();
+            return finishNode(factory.createTypeQueryNode(entityName, typeArguments), pos);
         }
 
         function parseTypeParameter(): TypeParameterDeclaration {
@@ -5428,23 +5431,33 @@ namespace ts {
                     continue;
                 }
 
-                if (!questionDotToken && token() === SyntaxKind.ExclamationToken && !scanner.hasPrecedingLineBreak()) {
-                    nextToken();
-                    expression = finishNode(factory.createNonNullExpression(expression), pos);
-                    continue;
-                }
-
                 // when in the [Decorator] context, we do not parse ElementAccess as it could be part of a ComputedPropertyName
                 if ((questionDotToken || !inDecoratorContext()) && parseOptional(SyntaxKind.OpenBracketToken)) {
                     expression = parseElementAccessExpressionRest(pos, expression, questionDotToken);
                     continue;
                 }
 
                 if (isTemplateStartOfTaggedTemplate()) {
-                    expression = parseTaggedTemplateRest(pos, expression, questionDotToken, /*typeArguments*/ undefined);
+                    // Absorb type arguments into TemplateExpression when preceding expression is ExpressionWithTypeArguments
+                    expression = !questionDotToken && expression.kind === SyntaxKind.ExpressionWithTypeArguments ?
+                        parseTaggedTemplateRest(pos, (expression as ExpressionWithTypeArguments).expression, questionDotToken, (expression as ExpressionWithTypeArguments).typeArguments) :
+                        parseTaggedTemplateRest(pos, expression, questionDotToken, /*typeArguments*/ undefined);
                     continue;
                 }
 
+                if (!questionDotToken) {
+                    if (token() === SyntaxKind.ExclamationToken && !scanner.hasPrecedingLineBreak()) {
+                        nextToken();
+                        expression = finishNode(factory.createNonNullExpression(expression), pos);
+                        continue;
+                    }
+                    const typeArguments = tryParse(parseTypeArgumentsInExpression);
+                    if (typeArguments) {
+                        expression = finishNode(factory.createExpressionWithTypeArguments(expression, typeArguments), pos);
+                        continue;
+                    }
+                }
+
                 return expression as MemberExpression;
             }
         }
@@ -5471,39 +5484,30 @@ namespace ts {
         function parseCallExpressionRest(pos: number, expression: LeftHandSideExpression): LeftHandSideExpression {
             while (true) {
                 expression = parseMemberExpressionRest(pos, expression, /*allowOptionalChain*/ true);
+                let typeArguments: NodeArray<TypeNode> | undefined;
                 const questionDotToken = parseOptionalToken(SyntaxKind.QuestionDotToken);
-                // handle 'foo<<T>()'
-                // parse template arguments only in TypeScript files (not in JavaScript files).
-                if ((contextFlags & NodeFlags.JavaScriptFile) === 0 && (token() === SyntaxKind.LessThanToken || token() === SyntaxKind.LessThanLessThanToken)) {
-                    // See if this is the start of a generic invocation.  If so, consume it and
-                    // keep checking for postfix expressions.  Otherwise, it's just a '<' that's
-                    // part of an arithmetic expression.  Break out so we consume it higher in the
-                    // stack.
-                    const typeArguments = tryParse(parseTypeArgumentsInExpression);
-                    if (typeArguments) {
-                        if (isTemplateStartOfTaggedTemplate()) {
-                            expression = parseTaggedTemplateRest(pos, expression, questionDotToken, typeArguments);
-                            continue;
-                        }
-
-                        const argumentList = parseArgumentList();
-                        const callExpr = questionDotToken || tryReparseOptionalChain(expression) ?
-                            factory.createCallChain(expression, questionDotToken, typeArguments, argumentList) :
-                            factory.createCallExpression(expression, typeArguments, argumentList);
-                        expression = finishNode(callExpr, pos);
+                if (questionDotToken) {
+                    typeArguments = tryParse(parseTypeArgumentsInExpression);
+                    if (isTemplateStartOfTaggedTemplate()) {
+                        expression = parseTaggedTemplateRest(pos, expression, questionDotToken, typeArguments);
                         continue;
                     }
                 }
-                else if (token() === SyntaxKind.OpenParenToken) {
+                if (typeArguments || token() === SyntaxKind.OpenParenToken) {
+                    // Absorb type arguments into CallExpression when preceding expression is ExpressionWithTypeArguments
+                    if (!questionDotToken && expression.kind === SyntaxKind.ExpressionWithTypeArguments) {
+                        typeArguments = (expression as ExpressionWithTypeArguments).typeArguments;
+                        expression = (expression as ExpressionWithTypeArguments).expression;
+                    }
                     const argumentList = parseArgumentList();
                     const callExpr = questionDotToken || tryReparseOptionalChain(expression) ?
-                        factory.createCallChain(expression, questionDotToken, /*typeArguments*/ undefined, argumentList) :
-                        factory.createCallExpression(expression, /*typeArguments*/ undefined, argumentList);
+                        factory.createCallChain(expression, questionDotToken, typeArguments, argumentList) :
+                        factory.createCallExpression(expression, typeArguments, argumentList);
                     expression = finishNode(callExpr, pos);
                     continue;
                 }
                 if (questionDotToken) {
-                    // We failed to parse anything, so report a missing identifier here.
+                    // We parsed `?.` but then failed to parse anything, so report a missing identifier here.
                     const name = createMissingNode<Identifier>(SyntaxKind.Identifier, /*reportAtCurrentPosition*/ false, Diagnostics.Identifier_expected);
                     expression = finishNode(factory.createPropertyAccessChain(expression, questionDotToken, name), pos);
                 }
@@ -5536,22 +5540,26 @@ namespace ts {
                 return undefined;
             }
 
-            // If we have a '<', then only parse this as a argument list if the type arguments
-            // are complete and we have an open paren.  if we don't, rewind and return nothing.
-            return typeArguments && canFollowTypeArgumentsInExpression()
-                ? typeArguments
-                : undefined;
+            // We successfully parsed a type argument list. The next token determines whether we want to
+            // treat it as such. If the type argument list is followed by `(` or a template literal, as in
+            // `f<number>(42)`, we favor the type argument interpretation even though JavaScript would view
+            // it as a relational expression.
+            return typeArguments && canFollowTypeArgumentsInExpression() ? typeArguments : undefined;
         }
 
         function canFollowTypeArgumentsInExpression(): boolean {
             switch (token()) {
+                // These tokens can follow a type argument list in a call expression.
                 case SyntaxKind.OpenParenToken:                 // foo<x>(
                 case SyntaxKind.NoSubstitutionTemplateLiteral:  // foo<T> `...`
                 case SyntaxKind.TemplateHead:                   // foo<T> `...${100}...`
-                // these are the only tokens can legally follow a type argument
-                // list. So we definitely want to treat them as type arg lists.
+                // These tokens can't follow in a call expression, nor can they start an
+                // expression. So, consider the type argument list part of an instantiation
+                // expression.
                 // falls through
+                case SyntaxKind.CommaToken:                     // foo<x>,
                 case SyntaxKind.DotToken:                       // foo<x>.
+                case SyntaxKind.QuestionDotToken:               // foo<x>?.
                 case SyntaxKind.CloseParenToken:                // foo<x>)
                 case SyntaxKind.CloseBracketToken:              // foo<x>]
                 case SyntaxKind.ColonToken:                     // foo<x>:
@@ -5569,21 +5577,10 @@ namespace ts {
                 case SyntaxKind.BarToken:                       // foo<x> |
                 case SyntaxKind.CloseBraceToken:                // foo<x> }
                 case SyntaxKind.EndOfFileToken:                 // foo<x>
-                    // these cases can't legally follow a type arg list.  However, they're not legal
-                    // expressions either.  The user is probably in the middle of a generic type. So
-                    // treat it as such.
                     return true;
-
-                case SyntaxKind.CommaToken:                     // foo<x>,
-                case SyntaxKind.OpenBraceToken:                 // foo<x> {
-                // We don't want to treat these as type arguments.  Otherwise we'll parse this
-                // as an invocation expression.  Instead, we want to parse out the expression
-                // in isolation from the type arguments.
-                // falls through
-                default:
-                    // Anything else treat as an expression.
-                    return false;
             }
+            // Treat anything else as an expression.
+            return false;
         }
 
         function parsePrimaryExpression(): PrimaryExpression {
@@ -5790,30 +5787,16 @@ namespace ts {
                 const name = parseIdentifierName();
                 return finishNode(factory.createMetaProperty(SyntaxKind.NewKeyword, name), pos);
             }
-
             const expressionPos = getNodePos();
-            let expression: MemberExpression = parsePrimaryExpression();
-            let typeArguments;
-            while (true) {
-                expression = parseMemberExpressionRest(expressionPos, expression, /*allowOptionalChain*/ false);
-                typeArguments = tryParse(parseTypeArgumentsInExpression);
-                if (isTemplateStartOfTaggedTemplate()) {
-                    Debug.assert(!!typeArguments,
-                        "Expected a type argument list; all plain tagged template starts should be consumed in 'parseMemberExpressionRest'");
-                    expression = parseTaggedTemplateRest(expressionPos, expression, /*optionalChain*/ undefined, typeArguments);
-                    typeArguments = undefined;
-                }
-                break;
+            let expression: LeftHandSideExpression = parseMemberExpressionRest(expressionPos, parsePrimaryExpression(), /*allowOptionalChain*/ false);
+            let typeArguments: NodeArray<TypeNode> | undefined;
+            // Absorb type arguments into NewExpression when preceding expression is ExpressionWithTypeArguments
+            if (expression.kind === SyntaxKind.ExpressionWithTypeArguments) {
+                typeArguments = (expression as ExpressionWithTypeArguments).typeArguments;
+                expression = (expression as ExpressionWithTypeArguments).expression;
             }
-
-            let argumentsArray: NodeArray<Expression> | undefined;
-            if (token() === SyntaxKind.OpenParenToken) {
-                argumentsArray = parseArgumentList();
-            }
-            else if (typeArguments) {
-                parseErrorAt(pos, scanner.getStartPos(), Diagnostics.A_new_expression_with_type_arguments_must_always_be_followed_by_a_parenthesized_argument_list);
-            }
-            return finishNode(factory.createNewExpression(expression, typeArguments, argumentsArray), pos);
+            const argumentList = token() === SyntaxKind.OpenParenToken ? parseArgumentList() : undefined;
+            return finishNode(factory.createNewExpression(expression, typeArguments, argumentList), pos);
         }
 
         // STATEMENTS
@@ -7071,6 +7054,9 @@ namespace ts {
         function parseExpressionWithTypeArguments(): ExpressionWithTypeArguments {
             const pos = getNodePos();
             const expression = parseLeftHandSideExpressionOrHigher();
+            if (expression.kind === SyntaxKind.ExpressionWithTypeArguments) {
+                return expression as ExpressionWithTypeArguments;
+            }
             const typeArguments = tryParseTypeArguments();
             return finishNode(factory.createExpressionWithTypeArguments(expression, typeArguments), pos);
         }