microsoft · rbuckton · Sep 29, 2023 · Jul 17, 2023 · Jul 17, 2023 · Jul 17, 2023
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -3659,6 +3659,18 @@
         "category": "Error",
         "code": 2854
     },
+    "The left-hand side of an 'instanceof' expression must be assignable to the first argument of the right-hand side's '[Symbol.hasInstance]' method.": {
+        "category": "Error",
+        "code": 2855
+    },
+    "An object's '[Symbol.hasInstance]' method must return a boolean value for it to be used on the right-hand side of an 'instanceof' expression.": {
+        "category": "Error",
+        "code": 2856
+    },
+    "The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.": {
+        "category": "Error",
+        "code": 2857
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -2485,7 +2485,7 @@ export interface YieldExpression extends Expression {
     readonly expression?: Expression;
 }
 
-export interface SyntheticExpression extends Expression {
+export interface SyntheticExpression extends LeftHandSideExpression {
     readonly kind: SyntaxKind.SyntheticExpression;
     readonly isSpread: boolean;
     readonly type: Type;
@@ -6564,6 +6564,11 @@ export interface PromiseOrAwaitableType extends ObjectType, UnionType {
     awaitedTypeOfType?: Type;
 }
 
+/** @internal */
+export interface HasInstanceMethodType extends Type {
+    hasSimpleUnrestrictedSingleCallSignature?: boolean;
+}
+
 /** @internal */
 export interface SyntheticDefaultModuleType extends Type {
     syntheticType?: Type;

diff --git a/src/compiler/utilitiesPublic.ts b/src/compiler/utilitiesPublic.ts
@@ -1978,6 +1978,7 @@ function isLeftHandSideExpressionKind(kind: SyntaxKind): boolean {
         case SyntaxKind.MetaProperty:
         case SyntaxKind.ImportKeyword: // technically this is only an Expression if it's in a CallExpression
         case SyntaxKind.MissingDeclaration:
+        case SyntaxKind.SyntheticExpression: // synthetic expressions are only used by the checker to substitute specific types for expression positions, so their precedence does not matter.
             return true;
         default:
             return false;

diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -5139,7 +5139,7 @@ declare namespace ts {
         readonly asteriskToken?: AsteriskToken;
         readonly expression?: Expression;
     }
-    interface SyntheticExpression extends Expression {
+    interface SyntheticExpression extends LeftHandSideExpression {
         readonly kind: SyntaxKind.SyntheticExpression;
         readonly isSpread: boolean;
         readonly type: Type;

diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -1086,7 +1086,7 @@ declare namespace ts {
         readonly asteriskToken?: AsteriskToken;
         readonly expression?: Expression;
     }
-    interface SyntheticExpression extends Expression {
+    interface SyntheticExpression extends LeftHandSideExpression {
         readonly kind: SyntaxKind.SyntheticExpression;
         readonly isSpread: boolean;
         readonly type: Type;

diff --git a/tests/baselines/reference/instanceofOperatorWithInvalidOperands.es2015.errors.txt b/tests/baselines/reference/instanceofOperatorWithInvalidOperands.es2015.errors.txt
@@ -0,0 +1,132 @@
+instanceofOperatorWithInvalidOperands.es2015.ts(14,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(15,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(16,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(17,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(18,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(19,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(20,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(21,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(22,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(34,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(35,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(36,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(37,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(38,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(39,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(40,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(41,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(42,24): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(43,25): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(46,11): error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+instanceofOperatorWithInvalidOperands.es2015.ts(46,25): error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+instanceofOperatorWithInvalidOperands.es2015.ts(51,12): error TS2855: The left-hand side of an 'instanceof' expression must be assignable to the first argument of the right-hand side's '[Symbol.hasInstance]' method.
+  Argument of type '{ y: string; }' is not assignable to parameter of type '{ x: number; }'.
+    Property 'x' is missing in type '{ y: string; }' but required in type '{ x: number; }'.
+instanceofOperatorWithInvalidOperands.es2015.ts(55,25): error TS2856: An object's '[Symbol.hasInstance]' method must return a boolean value for it to be used on the right-hand side of an 'instanceof' expression.
+
+
+==== instanceofOperatorWithInvalidOperands.es2015.ts (23 errors) ====
+    class C {
+        foo() { }
+    }
+
+    var x: any;
+
+    // invalid left operand
+    // the left operand is required to be of type Any, an object type, or a type parameter type
+    var a1: number;
+    var a2: boolean;
+    var a3: string;
+    var a4: void;
+
+    var ra1 = a1 instanceof x;
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra2 = a2 instanceof x;
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra3 = a3 instanceof x;
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra4 = a4 instanceof x;
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra5 = 0 instanceof x;
+              ~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra6 = true instanceof x;
+              ~~~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra7 = '' instanceof x;
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra8 = null instanceof x;
+              ~~~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+    var ra9 = undefined instanceof x;
+              ~~~~~~~~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+
+    // invalid right operand
+    // the right operand to be of type Any or a subtype of the 'Function' interface type
+    var b1: number;
+    var b2: boolean;
+    var b3: string;
+    var b4: void;
+    var o1: {};
+    var o2: Object;
+    var o3: C;
+
+    var rb1 = x instanceof b1;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb2 = x instanceof b2;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb3 = x instanceof b3;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb4 = x instanceof b4;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb5 = x instanceof 0;
+                           ~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb6 = x instanceof true;
+                           ~~~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb7 = x instanceof '';
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb8 = x instanceof o1;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb9 = x instanceof o2;
+                           ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+    var rb10 = x instanceof o3;
+                            ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+
+    // both operands are invalid
+    var rc1 = '' instanceof {};
+              ~~
+!!! error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
+                            ~~
+!!! error TS2857: The right-hand side of an 'instanceof' expression must be either of type 'any', an object type with a '[Symbol.hasInstance]()' method, or a type assignable to the 'Function' interface type.
+
+    // @@hasInstance restricts LHS
+    var o4: {[Symbol.hasInstance](value: { x: number }): boolean;};
+    var o5: { y: string };
+    var ra10 = o5 instanceof o4;
+               ~~
+!!! error TS2855: The left-hand side of an 'instanceof' expression must be assignable to the first argument of the right-hand side's '[Symbol.hasInstance]' method.
+!!! error TS2855:   Argument of type '{ y: string; }' is not assignable to parameter of type '{ x: number; }'.
+!!! error TS2855:     Property 'x' is missing in type '{ y: string; }' but required in type '{ x: number; }'.
+!!! related TS2728 instanceofOperatorWithInvalidOperands.es2015.ts:49:40: 'x' is declared here.
+
+    // invalid @@hasInstance method return type on RHS
+    var o6: {[Symbol.hasInstance](value: unknown): number;};
+    var rb11 = x instanceof o6;
+                            ~~
+!!! error TS2856: An object's '[Symbol.hasInstance]' method must return a boolean value for it to be used on the right-hand side of an 'instanceof' expression.
diff --git a/tests/baselines/reference/instanceofOperatorWithInvalidOperands.es2015.js b/tests/baselines/reference/instanceofOperatorWithInvalidOperands.es2015.js
@@ -0,0 +1,107 @@
+//// [tests/cases/conformance/expressions/binaryOperators/instanceofOperator/instanceofOperatorWithInvalidOperands.es2015.ts] ////
+
+//// [instanceofOperatorWithInvalidOperands.es2015.ts]
+class C {
+    foo() { }
+}
+
+var x: any;
+
+// invalid left operand
+// the left operand is required to be of type Any, an object type, or a type parameter type
+var a1: number;
+var a2: boolean;
+var a3: string;
+var a4: void;
+
+var ra1 = a1 instanceof x;
+var ra2 = a2 instanceof x;
+var ra3 = a3 instanceof x;
+var ra4 = a4 instanceof x;
+var ra5 = 0 instanceof x;
+var ra6 = true instanceof x;
+var ra7 = '' instanceof x;
+var ra8 = null instanceof x;
+var ra9 = undefined instanceof x;
+
+// invalid right operand
+// the right operand to be of type Any or a subtype of the 'Function' interface type
+var b1: number;
+var b2: boolean;
+var b3: string;
+var b4: void;
+var o1: {};
+var o2: Object;
+var o3: C;
+
+var rb1 = x instanceof b1;
+var rb2 = x instanceof b2;
+var rb3 = x instanceof b3;
+var rb4 = x instanceof b4;
+var rb5 = x instanceof 0;
+var rb6 = x instanceof true;
+var rb7 = x instanceof '';
+var rb8 = x instanceof o1;
+var rb9 = x instanceof o2;
+var rb10 = x instanceof o3;
+
+// both operands are invalid
+var rc1 = '' instanceof {};
+
+// @@hasInstance restricts LHS
+var o4: {[Symbol.hasInstance](value: { x: number }): boolean;};
+var o5: { y: string };
+var ra10 = o5 instanceof o4;
+
+// invalid @@hasInstance method return type on RHS
+var o6: {[Symbol.hasInstance](value: unknown): number;};
+var rb11 = x instanceof o6;
+
+//// [instanceofOperatorWithInvalidOperands.es2015.js]
+class C {
+    foo() { }
+}
+var x;
+// invalid left operand
+// the left operand is required to be of type Any, an object type, or a type parameter type
+var a1;
+var a2;
+var a3;
+var a4;
+var ra1 = a1 instanceof x;
+var ra2 = a2 instanceof x;
+var ra3 = a3 instanceof x;
+var ra4 = a4 instanceof x;
+var ra5 = 0 instanceof x;
+var ra6 = true instanceof x;
+var ra7 = '' instanceof x;
+var ra8 = null instanceof x;
+var ra9 = undefined instanceof x;
+// invalid right operand
+// the right operand to be of type Any or a subtype of the 'Function' interface type
+var b1;
+var b2;
+var b3;
+var b4;
+var o1;
+var o2;
+var o3;
+var rb1 = x instanceof b1;
+var rb2 = x instanceof b2;
+var rb3 = x instanceof b3;
+var rb4 = x instanceof b4;
+var rb5 = x instanceof 0;
+var rb6 = x instanceof true;
+var rb7 = x instanceof '';
+var rb8 = x instanceof o1;
+var rb9 = x instanceof o2;
+var rb10 = x instanceof o3;
+// both operands are invalid
+var rc1 = '' instanceof {};
+// @@hasInstance restricts LHS
+var o4;
+var o5;
+var ra10 = o5 instanceof o4;
+// invalid @@hasInstance method return type on RHS
+var o6;
+var rb11 = x instanceof o6;