Fix precedence of @this

Previously, both `@class` and `@this` in a jsdoc would cause the `@this`
annotation to be ignored. This became a worse problem with this PR,
because `this` is correctly typed even without the annotation.

This commit makes sure that `@this` is checked first and used if
present.

Author: sandersn

src/compiler/checker.ts

@@ -22436,21 +22436,23 @@ namespace ts {
             const isInJS = isInJSFile(node);
             if (isFunctionLike(container) &&
                 (!isInParameterInitializerBeforeContainingFunction(node) || getThisParameter(container))) {
-                let thisType: Type | undefined;
+                let thisType = getThisTypeOfDeclaration(container) || isInJS && getTypeForThisExpressionFromJSDoc(container);
                 // Note: a parameter initializer should refer to class-this unless function-this is explicitly annotated.
                 // If this is a function in a JS file, it might be a class method.
-                const className = getClassNameFromPrototypeMethod(container);
-                if (isInJS && className) {
-                    const classSymbol = checkExpression(className).symbol;
-                    if (classSymbol && classSymbol.members && (classSymbol.flags & SymbolFlags.Function)) {
-                        thisType = (getDeclaredTypeOfSymbol(classSymbol) as InterfaceType).thisType;
+                if (!thisType) {
+                    const className = getClassNameFromPrototypeMethod(container);
+                    if (isInJS && className) {
+                        const classSymbol = checkExpression(className).symbol;
+                        if (classSymbol && classSymbol.members && (classSymbol.flags & SymbolFlags.Function)) {
+                            thisType = (getDeclaredTypeOfSymbol(classSymbol) as InterfaceType).thisType;
+                        }
                     }
-                }
-                else if (isJSConstructor(container)) {
-                    thisType = (getDeclaredTypeOfSymbol(getMergedSymbol(container.symbol)) as InterfaceType).thisType;
+                    else if (isJSConstructor(container)) {
+                        thisType = (getDeclaredTypeOfSymbol(getMergedSymbol(container.symbol)) as InterfaceType).thisType;
+                    }
+                    thisType ||= getContextualThisParameterType(container);
                 }
 
-                thisType ||= getThisTypeOfDeclaration(container) || getContextualThisParameterType(container);
                 if (thisType) {
                     return getFlowTypeOfReference(node, thisType);
                 }
@@ -22462,12 +22464,6 @@ namespace ts {
                 return getFlowTypeOfReference(node, type);
             }
 
-            if (isInJS) {
-                const type = getTypeForThisExpressionFromJSDoc(container);
-                if (type && type !== errorType) {
-                    return getFlowTypeOfReference(node, type);
-                }
-            }
             if (isSourceFile(container)) {
                 // look up in the source file's locals or exports
                 if (container.commonJsModuleIndicator) {

tests/baselines/reference/assignmentToVoidZero2.errors.txt

@@ -1,11 +1,12 @@
 tests/cases/conformance/salsa/assignmentToVoidZero2.js(2,9): error TS2339: Property 'k' does not exist on type 'typeof import("tests/cases/conformance/salsa/assignmentToVoidZero2")'.
 tests/cases/conformance/salsa/assignmentToVoidZero2.js(5,3): error TS2339: Property 'y' does not exist on type 'typeof o'.
 tests/cases/conformance/salsa/assignmentToVoidZero2.js(6,9): error TS2339: Property 'y' does not exist on type 'typeof o'.
+tests/cases/conformance/salsa/assignmentToVoidZero2.js(10,10): error TS2339: Property 'q' does not exist on type 'C'.
 tests/cases/conformance/salsa/assignmentToVoidZero2.js(13,9): error TS2339: Property 'q' does not exist on type 'C'.
 tests/cases/conformance/salsa/importer.js(1,13): error TS2305: Module '"./assignmentToVoidZero2"' has no exported member 'k'.
 
 
-==== tests/cases/conformance/salsa/assignmentToVoidZero2.js (4 errors) ====
+==== tests/cases/conformance/salsa/assignmentToVoidZero2.js (5 errors) ====
     exports.j = 1;
     exports.k = void 0;
             ~
@@ -22,6 +23,8 @@ tests/cases/conformance/salsa/importer.js(1,13): error TS2305: Module '"./assign
     function C() {
         this.p = 1
         this.q = void 0
+             ~
+!!! error TS2339: Property 'q' does not exist on type 'C'.
     }
     var c = new C()
     c.p + c.q

tests/baselines/reference/assignmentToVoidZero2.symbols

@@ -28,9 +28,12 @@ function C() {
 >C : Symbol(C, Decl(assignmentToVoidZero2.js, 5, 9))
 
     this.p = 1
+>this.p : Symbol(C.p, Decl(assignmentToVoidZero2.js, 7, 14))
+>this : Symbol(C, Decl(assignmentToVoidZero2.js, 5, 9))
 >p : Symbol(C.p, Decl(assignmentToVoidZero2.js, 7, 14))
 
     this.q = void 0
+>this : Symbol(C, Decl(assignmentToVoidZero2.js, 5, 9))
 }
 var c = new C()
 >c : Symbol(c, Decl(assignmentToVoidZero2.js, 11, 3))

tests/baselines/reference/assignmentToVoidZero2.types

@@ -48,14 +48,14 @@ function C() {
     this.p = 1
 >this.p = 1 : 1
 >this.p : any
->this : any
+>this : this
 >p : any
 >1 : 1
 
     this.q = void 0
 >this.q = void 0 : undefined
 >this.q : any
->this : any
+>this : this
 >q : any
 >void 0 : undefined
 >0 : 0

tests/baselines/reference/constructorTagWithThisTag.symbols

@@ -0,0 +1,18 @@
+=== tests/cases/conformance/jsdoc/classthisboth.js ===
+/**
+ * @class
+ * @this {{ e: number, m: number }}
+ * this-tag should win, both 'e' and 'm' should be defined.
+ */
+function C() {
+>C : Symbol(C, Decl(classthisboth.js, 0, 0))
+
+    this.e = this.m + 1
+>this.e : Symbol(e, Decl(classthisboth.js, 2, 11))
+>this : Symbol(__type, Decl(classthisboth.js, 2, 10))
+>e : Symbol(C.e, Decl(classthisboth.js, 5, 14))
+>this.m : Symbol(m, Decl(classthisboth.js, 2, 22))
+>this : Symbol(__type, Decl(classthisboth.js, 2, 10))
+>m : Symbol(m, Decl(classthisboth.js, 2, 22))
+}
+

tests/baselines/reference/constructorTagWithThisTag.types

@@ -0,0 +1,21 @@
+=== tests/cases/conformance/jsdoc/classthisboth.js ===
+/**
+ * @class
+ * @this {{ e: number, m: number }}
+ * this-tag should win, both 'e' and 'm' should be defined.
+ */
+function C() {
+>C : typeof C
+
+    this.e = this.m + 1
+>this.e = this.m + 1 : number
+>this.e : number
+>this : { e: number; m: number; }
+>e : number
+>this.m + 1 : number
+>this.m : number
+>this : { e: number; m: number; }
+>m : number
+>1 : 1
+}
+

tests/cases/conformance/jsdoc/constructorTagWithThisTag.ts

@@ -0,0 +1,13 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @Filename: classthisboth.js
+
+/**
+ * @class
+ * @this {{ e: number, m: number }}
+ * this-tag should win, both 'e' and 'm' should be defined.
+ */
+function C() {
+    this.e = this.m + 1
+}