allow this in typeQuery

src/compiler/checker.ts

@@ -13200,7 +13200,8 @@ namespace ts {
                 // The expression is processed as an identifier expression (section 4.3)
                 // or property access expression(section 4.10),
                 // the widened type(section 3.9) of which becomes the result.
-                links.resolvedType = getRegularTypeOfLiteralType(getWidenedType(checkExpression(node.exprName)));
+                const type = isThisIdentifier(node.exprName) ? checkThisExpression(node.exprName) : checkExpression(node.exprName);
+                links.resolvedType = getRegularTypeOfLiteralType(getWidenedType(type));
             }
             return links.resolvedType;
         }
@@ -21997,9 +21998,11 @@ namespace ts {
                         && (source as MetaProperty).name.escapedText === (target as MetaProperty).name.escapedText;
                 case SyntaxKind.Identifier:
                 case SyntaxKind.PrivateIdentifier:
-                    return target.kind === SyntaxKind.Identifier && getResolvedSymbol(source as Identifier) === getResolvedSymbol(target as Identifier) ||
-                        (target.kind === SyntaxKind.VariableDeclaration || target.kind === SyntaxKind.BindingElement) &&
-                        getExportSymbolOfValueSymbolIfExported(getResolvedSymbol(source as Identifier)) === getSymbolOfNode(target);
+                    return isThisInTypeQuery(source) ?
+                        target.kind === SyntaxKind.ThisKeyword :
+                        target.kind === SyntaxKind.Identifier && getResolvedSymbol(source as Identifier) === getResolvedSymbol(target as Identifier) ||
+                            (target.kind === SyntaxKind.VariableDeclaration || target.kind === SyntaxKind.BindingElement) &&
+                            getExportSymbolOfValueSymbolIfExported(getResolvedSymbol(source as Identifier)) === getSymbolOfNode(target);
                 case SyntaxKind.ThisKeyword:
                     return target.kind === SyntaxKind.ThisKeyword;
                 case SyntaxKind.SuperKeyword:
@@ -24529,6 +24532,7 @@ namespace ts {
         }
 
         function checkThisExpression(node: Node): Type {
+            const isNodeInTypeQuery = isInTypeQuery(node);
             // Stop at the first arrow function so that we can
             // tell whether 'this' needs to be captured.
             let container = getThisContainer(node, /* includeArrowFunctions */ true);
@@ -24572,7 +24576,7 @@ namespace ts {
             }
 
             // When targeting es6, mark that we'll need to capture `this` in its lexically bound scope.
-            if (capturedByArrowFunction && languageVersion < ScriptTarget.ES2015) {
+            if (!isNodeInTypeQuery && capturedByArrowFunction && languageVersion < ScriptTarget.ES2015) {
                 captureLexicalThis(node, container);
             }
 
@@ -27275,7 +27279,8 @@ namespace ts {
         }
 
         function checkQualifiedName(node: QualifiedName, checkMode: CheckMode | undefined) {
-            return checkPropertyAccessExpressionOrQualifiedName(node, node.left, checkNonNullExpression(node.left), node.right, checkMode);
+            const leftType = isPartOfTypeQuery(node) && isThisIdentifier(node.left) ? checkNonNullType(checkThisExpression(node.left), node.left) : checkNonNullExpression(node.left);
+            return checkPropertyAccessExpressionOrQualifiedName(node, node.left, leftType, node.right, checkMode);
         }
 
         function isMethodAccessForCall(node: Node) {

src/compiler/utilities.ts

@@ -4348,6 +4348,18 @@ namespace ts {
         return !!node && node.kind === SyntaxKind.Identifier && identifierIsThisKeyword(node as Identifier);
     }
 
+    export function isThisInTypeQuery(node: Node): boolean {
+        if (!isThisIdentifier(node)) {
+            return false;
+        }
+
+        while (isQualifiedName(node.parent) && node.parent.left === node) {
+            node = node.parent;
+        }
+
+        return node.parent.kind === SyntaxKind.TypeQuery;
+    }
+
     export function identifierIsThisKeyword(id: Identifier): boolean {
         return id.originalKeywordKind === SyntaxKind.ThisKeyword;
     }

tests/baselines/reference/initializerReferencingConstructorLocals.errors.txt

@@ -1,12 +1,12 @@
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(4,9): error TS2304: Cannot find name 'z'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(5,15): error TS2304: Cannot find name 'z'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(6,14): error TS2339: Property 'z' does not exist on type 'C'.
-tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(7,15): error TS2304: Cannot find name 'this'.
+tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(7,20): error TS2339: Property 'z' does not exist on type 'C'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(9,9): error TS2304: Cannot find name 'z'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(14,9): error TS2304: Cannot find name 'z'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(15,15): error TS2304: Cannot find name 'z'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(16,14): error TS2339: Property 'z' does not exist on type 'D<T>'.
-tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(17,15): error TS2304: Cannot find name 'this'.
+tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(17,20): error TS2339: Property 'z' does not exist on type 'D<T>'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorLocals.ts(19,9): error TS2304: Cannot find name 'z'.
 
 
@@ -24,8 +24,8 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
                  ~
 !!! error TS2339: Property 'z' does not exist on type 'C'.
         d: typeof this.z; // error
-                  ~~~~
-!!! error TS2304: Cannot find name 'this'.
+                       ~
+!!! error TS2339: Property 'z' does not exist on type 'C'.
         constructor(x) {
             z = 1;
             ~
@@ -44,8 +44,8 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
                  ~
 !!! error TS2339: Property 'z' does not exist on type 'D<T>'.
         d: typeof this.z; // error
-                  ~~~~
-!!! error TS2304: Cannot find name 'this'.
+                       ~
+!!! error TS2339: Property 'z' does not exist on type 'D<T>'.
         constructor(x: T) {
             z = 1;
             ~

tests/baselines/reference/initializerReferencingConstructorParameters.errors.txt

@@ -2,11 +2,10 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(5,15): error TS2304: Cannot find name 'x'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(10,9): error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(11,15): error TS2304: Cannot find name 'x'.
-tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(17,15): error TS2304: Cannot find name 'this'.
 tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts(23,9): error TS2663: Cannot find name 'x'. Did you mean the instance member 'this.x'?
 
 
-==== tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts (6 errors) ====
+==== tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencingConstructorParameters.ts (5 errors) ====
     // Initializer expressions for instance member variables are evaluated in the scope of the class constructor body but are not permitted to reference parameters or local variables of the constructor. 
 
     class C {
@@ -31,9 +30,7 @@ tests/cases/conformance/classes/propertyMemberDeclarations/initializerReferencin
 
     class E {
         a = this.x; // ok
-        b: typeof this.x; // error
-                  ~~~~
-!!! error TS2304: Cannot find name 'this'.
+        b: typeof this.x; // ok
         constructor(public x) { }
     }
 

tests/baselines/reference/initializerReferencingConstructorParameters.js

@@ -15,7 +15,7 @@ class D {
 
 class E {
     a = this.x; // ok
-    b: typeof this.x; // error
+    b: typeof this.x; // ok
     constructor(public x) { }
 }
 

tests/baselines/reference/initializerReferencingConstructorParameters.symbols

@@ -36,8 +36,10 @@ class E {
 >this : Symbol(E, Decl(initializerReferencingConstructorParameters.ts, 12, 1))
 >x : Symbol(E.x, Decl(initializerReferencingConstructorParameters.ts, 17, 16))
 
-    b: typeof this.x; // error
+    b: typeof this.x; // ok
 >b : Symbol(E.b, Decl(initializerReferencingConstructorParameters.ts, 15, 15))
+>this.x : Symbol(E.x, Decl(initializerReferencingConstructorParameters.ts, 17, 16))
+>x : Symbol(E.x, Decl(initializerReferencingConstructorParameters.ts, 17, 16))
 
     constructor(public x) { }
 >x : Symbol(E.x, Decl(initializerReferencingConstructorParameters.ts, 17, 16))

tests/baselines/reference/initializerReferencingConstructorParameters.types

@@ -40,7 +40,7 @@ class E {
 >this : this
 >x : any
 
-    b: typeof this.x; // error
+    b: typeof this.x; // ok
 >b : any
 >this.x : any
 >this : any

tests/baselines/reference/typeofThis.errors.txt

@@ -0,0 +1,149 @@
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(24,19): error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(32,19): error TS2532: Object is possibly 'undefined'.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(46,23): error TS2331: 'this' cannot be referenced in a module or namespace body.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(46,23): error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(52,23): error TS2331: 'this' cannot be referenced in a module or namespace body.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(52,23): error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(57,19): error TS7041: The containing arrow function captures the global value of 'this'.
+tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts(57,24): error TS7017: Element implicitly has an 'any' type because type 'typeof globalThis' has no index signature.
+
+
+==== tests/cases/conformance/types/specifyingTypes/typeQueries/typeofThis.ts (8 errors) ====
+    class Test {
+        data = {};
+        constructor() {
+            var copy: typeof this.data = {};
+        }
+    }
+
+    class Test1 {
+        data = { foo: '' };
+        ['this'] = '';
+        constructor() {
+            var copy: typeof this.data = { foo: '' };
+            var foo: typeof this.data.foo = '';
+
+            var self: typeof this = this;
+            self.data;
+
+            var str: typeof this.this = '';
+        }
+    }
+
+
+    function Test2() {
+        let x: typeof this.no = 1;
+                      ~~~~
+!!! error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+    }
+
+    function Test3(this: { no: number }) {
+        let x: typeof this.no = 1;
+    }
+
+    function Test4(this: { no: number } | undefined) {
+        let x: typeof this.no = 1;
+                      ~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    }
+
+    class Test5 {
+        no = 1;
+
+        f = () => {
+            // should not capture this.
+            let x: typeof this.no = 1;
+        }
+    }
+
+    namespace Test6 {
+        export let f = () => {
+            let x: typeof this.no = 1;
+                          ~~~~
+!!! error TS2331: 'this' cannot be referenced in a module or namespace body.
+                          ~~~~
+!!! error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+        }
+    }
+
+    module Test7 {
+        export let f = () => {
+            let x: typeof this.no = 1;
+                          ~~~~
+!!! error TS2331: 'this' cannot be referenced in a module or namespace body.
+                          ~~~~
+!!! error TS2683: 'this' implicitly has type 'any' because it does not have a type annotation.
+        }
+    }
+
+    const Test8 = () => {
+        let x: typeof this.no = 1;
+                      ~~~~
+!!! error TS7041: The containing arrow function captures the global value of 'this'.
+                           ~~
+!!! error TS7017: Element implicitly has an 'any' type because type 'typeof globalThis' has no index signature.
+    }
+
+    class Test9 {
+        no = 0;
+        this = 0;
+
+        f() {
+            if (this instanceof Test9D1) {
+                const d1: typeof this = this;
+                d1.f1();
+            }
+
+            if (this instanceof Test9D2) {
+                const d2: typeof this = this;
+                d2.f2();
+            }
+        }
+
+        g() {
+            if (this.no === 1) {
+                const no: typeof this.no = this.no;
+            }
+
+            if (this.this === 1) {
+                const no: typeof this.this = this.this;
+            }
+        }
+    }
+
+    class Test9D1 {
+        f1() {}
+    }
+
+    class Test9D2 {
+        f2() {}
+    }
+
+    class Test10 {
+        a?: { b?: string }
+
+        foo() {
+            let a: typeof this.a = undefined as any;
+            if (this.a) {
+                let a: typeof this.a = undefined as any;    // should narrow to { b?: string }
+                let b: typeof this.a.b = undefined as any;
+
+                if (this.a.b) {
+                    let b: typeof this.a.b = undefined as any;   // should narrow to string
+                }
+            }
+        }
+    }
+
+    class Test11 {
+        this?: { x?: string };
+
+        foo() {
+            const o = this;
+            let bar: typeof o.this = {};
+
+            if (o.this && o.this.x) {
+                let y: string = o.this.x;   // should narrow to string
+            }
+        }
+    }