Instantiation expression can be followed by line break or binary operator (#49353)

* Allow instantiation expression to be followed by let or interface on new line

* Add tests

* Update src/compiler/parser.ts

* Instantiation expressions followed by line breaks or binary operators

* Add more tests

* Accept new baselines

* Fix lint error

* Update fourslash test

Co-authored-by: Daniel Rosenwasser <[email protected]>

Author: ahejlsberg

src/compiler/parser.ts

@@ -5783,9 +5783,18 @@ namespace ts {
                 case SyntaxKind.NoSubstitutionTemplateLiteral:  // foo<T> `...`
                 case SyntaxKind.TemplateHead:                   // foo<T> `...${100}...`
                     return true;
+                // A type argument list followed by `<` never makes sense, and a type argument list followed
+                // by `>` is ambiguous with a (re-scanned) `>>` operator, so we disqualify both. Also, in
+                // this context, `+` and `-` are unary operators, not binary operators.
+                case SyntaxKind.LessThanToken:
+                case SyntaxKind.GreaterThanToken:
+                case SyntaxKind.PlusToken:
+                case SyntaxKind.MinusToken:
+                    return false;
             }
-            // Consider something a type argument list only if the following token can't start an expression.
-            return !isStartOfExpression();
+            // We favor the type argument list interpretation when it is immediately followed by
+            // a line break, a binary operator, or something that can't start an expression.
+            return scanner.hasPrecedingLineBreak() || isBinaryOperator() || !isStartOfExpression();
         }
 
         function parsePrimaryExpression(): PrimaryExpression {

tests/baselines/reference/instantiationExpressionErrors.errors.txt

@@ -6,11 +6,15 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpr
 tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(19,24): error TS2635: Type '{ (): number; g<U>(): U; }' has no signatures for which the type argument list is applicable.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(23,23): error TS1005: '(' expected.
 tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(26,24): error TS2558: Expected 0 type arguments, but got 1.
-tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(31,2): error TS2554: Expected 0 arguments, but got 1.
-tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(35,12): error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(39,2): error TS2554: Expected 0 arguments, but got 1.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(43,12): error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(44,12): error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(44,12): error TS2365: Operator '>' cannot be applied to types 'boolean' and 'number'.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(45,12): error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts(45,12): error TS2365: Operator '>' cannot be applied to types 'boolean' and 'number'.
 
 
-==== tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts (10 errors) ====
+==== tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpressionErrors.ts (14 errors) ====
     declare let f: { <T>(): T, g<U>(): U };
 
     // Type arguments in member expressions
@@ -54,27 +58,86 @@ tests/cases/conformance/types/typeParameters/typeArgumentLists/instantiationExpr
                            ~~~~~~
 !!! error TS2558: Expected 0 type arguments, but got 1.
 
+    // Instantiation expression and binary operators
+    
+    declare let g: (<T>(x: T) => T) | undefined;
+    
+    const c1 = g<string> || ((x: string) => x);
+    const c2 = g<string> ?? ((x: string) => x);
+    const c3 = g<string> && ((x: string) => x);
+    
     // Parsed as function call, even though this differs from JavaScript
 
     const x1 = f<true>
     (true);
      ~~~~
 !!! error TS2554: Expected 0 arguments, but got 1.
 
-    // Parsed as relational expression
+    // Parsed as relational expressions
 
-    const x2 = f<true>
-               ~~~~~~
+    const r1 = f < true > true;
+               ~~~~~~~~
 !!! error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
-    true;
+    const r2 = f < true > +1;
+               ~~~~~~~~
+!!! error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+               ~~~~~~~~~~~~~
+!!! error TS2365: Operator '>' cannot be applied to types 'boolean' and 'number'.
+    const r3 = f < true > -1;
+               ~~~~~~~~
+!!! error TS2365: Operator '<' cannot be applied to types '{ <T>(): T; g<U>(): U; }' and 'boolean'.
+               ~~~~~~~~~~~~~
+!!! error TS2365: Operator '>' cannot be applied to types 'boolean' and 'number'.
 
-    // Parsed as instantiation expression
+    // All of the following are parsed as instantiation expressions
 
-    const x3 = f<true>;
+    const x2 = f<true>
     true;
 
-    // Parsed as instantiation expression
+    const x3 = f<true>;
+    true;
 
     const x4 = f<true>
     if (true) {}
+    
+    const x5 = f<true>
+    let yy = 0;
+    
+    const x6 = f<true>
+    interface I {}
+    
+    let x10 = f<true>
+    this.bar()
+    
+    let x11 = f<true>
+    function bar() {}
+    
+    let x12 = f<true>
+    class C {}
+    
+    let x13 = f<true>
+    bar()
+    
+    let x14 = f<true>
+    void bar()
+    
+    class C1 {
+        static specialFoo = f<string>
+        static bar = 123
+    }
+    
+    class C2 {
+        public specialFoo = f<string>
+        public bar = 123
+    }
+    
+    class C3 {
+        private specialFoo = f<string>
+        private bar = 123
+    }
+    
+    class C4 {
+        protected specialFoo = f<string>
+        protected bar = 123
+    }
 

tests/baselines/reference/instantiationExpressionErrors.js

@@ -26,30 +26,81 @@ const b2 = f?.<number>();
 const b3 = f<number>?.();
 const b4 = f<number>?.<number>();  // Error, expected no type arguments
 
+// Instantiation expression and binary operators
+
+declare let g: (<T>(x: T) => T) | undefined;
+
+const c1 = g<string> || ((x: string) => x);
+const c2 = g<string> ?? ((x: string) => x);
+const c3 = g<string> && ((x: string) => x);
+
 // Parsed as function call, even though this differs from JavaScript
 
 const x1 = f<true>
 (true);
 
-// Parsed as relational expression
+// Parsed as relational expressions
+
+const r1 = f < true > true;
+const r2 = f < true > +1;
+const r3 = f < true > -1;
+
+// All of the following are parsed as instantiation expressions
 
 const x2 = f<true>
 true;
 
-// Parsed as instantiation expression
-
 const x3 = f<true>;
 true;
 
-// Parsed as instantiation expression
-
 const x4 = f<true>
 if (true) {}
+
+const x5 = f<true>
+let yy = 0;
+
+const x6 = f<true>
+interface I {}
+
+let x10 = f<true>
+this.bar()
+
+let x11 = f<true>
+function bar() {}
+
+let x12 = f<true>
+class C {}
+
+let x13 = f<true>
+bar()
+
+let x14 = f<true>
+void bar()
+
+class C1 {
+    static specialFoo = f<string>
+    static bar = 123
+}
+
+class C2 {
+    public specialFoo = f<string>
+    public bar = 123
+}
+
+class C3 {
+    private specialFoo = f<string>
+    private bar = 123
+}
+
+class C4 {
+    protected specialFoo = f<string>
+    protected bar = 123
+}
 
 
 //// [instantiationExpressionErrors.js]
 "use strict";
-var _a, _b;
+var _a, _b, _c;
 // Type arguments in member expressions
 var a1 = (f); // { (): number; g<U>(): U; }
 var a2 = (f.g); // () => number
@@ -67,17 +118,67 @@ var b1 = f === null || f === void 0 ? void 0 : f(); // Error, `(` expected
 var b2 = f === null || f === void 0 ? void 0 : f();
 var b3 = (_a = (f)) === null || _a === void 0 ? void 0 : _a();
 var b4 = (_b = (f)) === null || _b === void 0 ? void 0 : _b(); // Error, expected no type arguments
+var c1 = (g) || (function (x) { return x; });
+var c2 = (_c = (g)) !== null && _c !== void 0 ? _c : (function (x) { return x; });
+var c3 = (g) && (function (x) { return x; });
 // Parsed as function call, even though this differs from JavaScript
 var x1 = f(true);
-// Parsed as relational expression
-var x2 = f < true >
-    true;
-// Parsed as instantiation expression
+// Parsed as relational expressions
+var r1 = f < true > true;
+var r2 = f < true > +1;
+var r3 = f < true > -1;
+// All of the following are parsed as instantiation expressions
+var x2 = (f);
+true;
 var x3 = (f);
 true;
-// Parsed as instantiation expression
 var x4 = (f);
 if (true) { }
+var x5 = (f);
+var yy = 0;
+var x6 = (f);
+var x10 = (f);
+this.bar();
+var x11 = (f);
+function bar() { }
+var x12 = (f);
+var C = /** @class */ (function () {
+    function C() {
+    }
+    return C;
+}());
+var x13 = (f);
+bar();
+var x14 = (f);
+void bar();
+var C1 = /** @class */ (function () {
+    function C1() {
+    }
+    C1.specialFoo = (f);
+    C1.bar = 123;
+    return C1;
+}());
+var C2 = /** @class */ (function () {
+    function C2() {
+        this.specialFoo = (f);
+        this.bar = 123;
+    }
+    return C2;
+}());
+var C3 = /** @class */ (function () {
+    function C3() {
+        this.specialFoo = (f);
+        this.bar = 123;
+    }
+    return C3;
+}());
+var C4 = /** @class */ (function () {
+    function C4() {
+        this.specialFoo = (f);
+        this.bar = 123;
+    }
+    return C4;
+}());
 
 
 //// [instantiationExpressionErrors.d.ts]
@@ -103,8 +204,18 @@ declare const b1: number;
 declare const b2: number;
 declare const b3: number;
 declare const b4: number;
+declare let g: (<T>(x: T) => T) | undefined;
+declare const c1: (x: string) => string;
+declare const c2: (x: string) => string;
+declare const c3: ((x: string) => string) | undefined;
 declare const x1: true;
-declare const x2: boolean;
+declare const r1: boolean;
+declare const r2: boolean;
+declare const r3: boolean;
+declare const x2: {
+    (): true;
+    g<U>(): U;
+};
 declare const x3: {
     (): true;
     g<U>(): U;
@@ -113,3 +224,62 @@ declare const x4: {
     (): true;
     g<U>(): U;
 };
+declare const x5: {
+    (): true;
+    g<U>(): U;
+};
+declare let yy: number;
+declare const x6: {
+    (): true;
+    g<U>(): U;
+};
+interface I {
+}
+declare let x10: {
+    (): true;
+    g<U>(): U;
+};
+declare let x11: {
+    (): true;
+    g<U>(): U;
+};
+declare function bar(): void;
+declare let x12: {
+    (): true;
+    g<U>(): U;
+};
+declare class C {
+}
+declare let x13: {
+    (): true;
+    g<U>(): U;
+};
+declare let x14: {
+    (): true;
+    g<U>(): U;
+};
+declare class C1 {
+    static specialFoo: {
+        (): string;
+        g<U>(): U;
+    };
+    static bar: number;
+}
+declare class C2 {
+    specialFoo: {
+        (): string;
+        g<U>(): U;
+    };
+    bar: number;
+}
+declare class C3 {
+    private specialFoo;
+    private bar;
+}
+declare class C4 {
+    protected specialFoo: {
+        (): string;
+        g<U>(): U;
+    };
+    protected bar: number;
+}