Fix 7304: show correct quickinfo on "this" in type position (#8508)

* Show correct quickinfo when using this in type position

* Split quickinfo test into smaller files and add test case

src/compiler/checker.ts

@@ -5211,6 +5211,7 @@ namespace ts {
                 case SyntaxKind.NullKeyword:
                     return nullType;
                 case SyntaxKind.ThisType:
+                case SyntaxKind.ThisKeyword:
                     return getTypeFromThisTypeNode(node);
                 case SyntaxKind.StringLiteralType:
                     return getTypeFromStringLiteralTypeNode(<StringLiteralTypeNode>node);
@@ -12509,7 +12510,7 @@ namespace ts {
 
         // Checks an expression and returns its type. The contextualMapper parameter serves two purposes: When
         // contextualMapper is not undefined and not equal to the identityMapper function object it indicates that the
-        // expression is being inferentially typed (section 4.12.2 in spec) and provides the type mapper to use in
+        // expression is being inferentially typed (section 4.15.2 in spec) and provides the type mapper to use in
         // conjunction with the generic contextual type. When contextualMapper is equal to the identityMapper function
         // object, it serves as an indicator that all contained function and arrow expressions should be considered to
         // have the wildcard function type; this form of type check is used during overload resolution to exclude

src/compiler/utilities.ts

@@ -1056,6 +1056,7 @@ namespace ts {
 
     export function isExpression(node: Node): boolean {
         switch (node.kind) {
+            case SyntaxKind.ThisKeyword:
             case SyntaxKind.SuperKeyword:
             case SyntaxKind.NullKeyword:
             case SyntaxKind.TrueKeyword:

tests/cases/fourslash/quickInfoOnThis.ts

@@ -5,6 +5,7 @@
 ////function wrapper(wrapped: { (): void; }) { }
 ////class Foo {
 ////    n: number;
+////    prop1: th/*0*/is;
 ////    public explicitThis(this: this) {
 ////        wrapper(
 ////            function explicitVoid(this: void) {
@@ -20,43 +21,9 @@
 ////        console.log(th/*6*/is);
 ////    }
 ////}
-////class Bar<T> {
-////    public explicitThis(this: this) {
-////        console.log(th/*7*/is);
-////    }
-////    public explicitClass(this: Bar<T>) {
-////        console.log(thi/*8*/s);
-////    }
-////}
-////
-////function implicitAny(x: number): void {
-////    return th/*9*/is;
-////}
-////function explicitVoid(th/*10*/is: void, x: number): void {
-////    return th/*11*/is;
-////}
-////function explicitInterface(th/*12*/is: Restricted): void {
-////    console.log(thi/*13*/s);
-////}
-////function explicitLiteral(th/*14*/is: { n: number }): void {
-////    console.log(th/*15*/is);
-////}
-////
-////interface ContextualInterface {
-////    m: number;
-////    method(this: this, n: number);
-////}
-////let o: ContextualInterface = {
-////    m: 12,
-////    method(n) {
-////        let x = this/*16*/.m;
-////    }
-////}
-////interface ContextualInterface2 {
-////    (this: void, n: number): void;
-////}
-////let contextualInterface2: ContextualInterface2 = function (th/*17*/is, n) { }
 
+goTo.marker('0');
+verify.quickInfoIs('this: this');
 goTo.marker('1');
 verify.quickInfoIs('void');
 goTo.marker('2');
@@ -68,28 +35,4 @@ verify.quickInfoIs('this: Restricted');
 goTo.marker('5');
 verify.quickInfoIs('(parameter) this: Foo');
 goTo.marker('6');
-verify.quickInfoIs('this: Foo');
-goTo.marker('7');
-verify.quickInfoIs('this: this');
-goTo.marker('8');
-verify.quickInfoIs('this: Bar<T>');
-goTo.marker('9');
-verify.quickInfoIs('any');
-goTo.marker('10');
-verify.quickInfoIs('(parameter) this: void');
-goTo.marker('11');
-verify.quickInfoIs('void');
-goTo.marker('12');
-verify.quickInfoIs('(parameter) this: Restricted');
-goTo.marker('13');
-verify.quickInfoIs('this: Restricted');
-goTo.marker('14');
-
-verify.quickInfoIs('(parameter) this: {\n    n: number;\n}');
-goTo.marker('15');
-verify.quickInfoIs('this: {\n    n: number;\n}');
-
-goTo.marker('16');
-verify.quickInfoIs('this: ContextualInterface');
-goTo.marker('17');
-verify.quickInfoIs('(parameter) this: void');
+verify.quickInfoIs('this: Foo');

tests/cases/fourslash/quickInfoOnThis2.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+////class Bar<T> {
+////    public explicitThis(this: this) {
+////        console.log(th/*1*/is);
+////    }
+////    public explicitClass(this: Bar<T>) {
+////        console.log(thi/*2*/s);
+////    }
+////}
+
+goTo.marker('1');
+verify.quickInfoIs('this: this');
+goTo.marker('2');
+verify.quickInfoIs('this: Bar<T>');

tests/cases/fourslash/quickInfoOnThis3.ts

@@ -0,0 +1,32 @@
+/// <reference path='fourslash.ts' />
+////interface Restricted {
+////    n: number;
+////}
+////function implicitAny(x: number): void {
+////    return th/*1*/is;
+////}
+////function explicitVoid(th/*2*/is: void, x: number): void {
+////    return th/*3*/is;
+////}
+////function explicitInterface(th/*4*/is: Restricted): void {
+////    console.log(thi/*5*/s);
+////}
+////function explicitLiteral(th/*6*/is: { n: number }): void {
+////    console.log(th/*7*/is);
+////}
+
+goTo.marker('1');
+verify.quickInfoIs('any');
+goTo.marker('2');
+verify.quickInfoIs('(parameter) this: void');
+goTo.marker('3');
+verify.quickInfoIs('void');
+goTo.marker('4');
+verify.quickInfoIs('(parameter) this: Restricted');
+goTo.marker('5');
+verify.quickInfoIs('this: Restricted');
+goTo.marker('6');
+
+verify.quickInfoIs('(parameter) this: {\n    n: number;\n}');
+goTo.marker('7');
+verify.quickInfoIs('this: {\n    n: number;\n}');

tests/cases/fourslash/quickInfoOnThis4.ts

@@ -0,0 +1,20 @@
+/// <reference path='fourslash.ts' />
+////interface ContextualInterface {
+////    m: number;
+////    method(this: this, n: number);
+////}
+////let o: ContextualInterface = {
+////    m: 12,
+////    method(n) {
+////        let x = this/*1*/.m;
+////    }
+////}
+////interface ContextualInterface2 {
+////    (this: void, n: number): void;
+////}
+////let contextualInterface2: ContextualInterface2 = function (th/*2*/is, n) { }
+
+goTo.marker('1');
+verify.quickInfoIs('this: ContextualInterface');
+goTo.marker('2');
+verify.quickInfoIs('(parameter) this: void');