fix(50952): Can't infer from this type on static class method call in JS Doc (#51149)

Co-authored-by: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>

src/compiler/checker.ts

@@ -14313,6 +14313,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 }
             }
 
+            if (isInJSFile(declaration)) {
+                const thisTag = getJSDocThisTag(declaration);
+                if (thisTag && thisTag.typeExpression) {
+                    thisParameter = createSymbolWithType(createSymbol(SymbolFlags.FunctionScopedVariable, InternalSymbolName.This), getTypeFromTypeNode(thisTag.typeExpression));
+                }
+            }
+
             const classType = declaration.kind === SyntaxKind.Constructor ?
                 getDeclaredTypeOfClassOrInterface(getMergedSymbol((declaration.parent as ClassDeclaration).symbol))
                 : undefined;

tests/baselines/reference/constructorTagWithThisTag.symbols

@@ -9,10 +9,10 @@ function C() {
 
     this.e = this.m + 1
 >this.e : Symbol(e, Decl(classthisboth.js, 2, 11))
->this : Symbol(__type, Decl(classthisboth.js, 2, 10))
+>this : Symbol(this)
 >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))
+>this : Symbol(this)
 >m : Symbol(m, Decl(classthisboth.js, 2, 22))
 }
 

tests/baselines/reference/inferThis.symbols

@@ -0,0 +1,51 @@
+=== /a.js ===
+export class C {
+>C : Symbol(C, Decl(a.js, 0, 0))
+
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    static a() {
+>a : Symbol(C.a, Decl(a.js, 0, 16))
+
+        return this;
+>this : Symbol(this)
+    }
+
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    b() {
+>b : Symbol(C.b, Decl(a.js, 8, 5))
+
+        return this;
+>this : Symbol(this)
+    }
+}
+
+const a = C.a();
+>a : Symbol(a, Decl(a.js, 20, 5))
+>C.a : Symbol(C.a, Decl(a.js, 0, 16))
+>C : Symbol(C, Decl(a.js, 0, 0))
+>a : Symbol(C.a, Decl(a.js, 0, 16))
+
+a; // typeof C
+>a : Symbol(a, Decl(a.js, 20, 5))
+
+const c = new C();
+>c : Symbol(c, Decl(a.js, 23, 5))
+>C : Symbol(C, Decl(a.js, 0, 0))
+
+const b = c.b();
+>b : Symbol(b, Decl(a.js, 24, 5))
+>c.b : Symbol(C.b, Decl(a.js, 8, 5))
+>c : Symbol(c, Decl(a.js, 23, 5))
+>b : Symbol(C.b, Decl(a.js, 8, 5))
+
+b; // C
+>b : Symbol(b, Decl(a.js, 24, 5))
+

tests/baselines/reference/inferThis.types

@@ -0,0 +1,54 @@
+=== /a.js ===
+export class C {
+>C : C
+
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    static a() {
+>a : <T>(this: T) => T
+
+        return this;
+>this : T
+    }
+
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    b() {
+>b : <T>(this: T) => T
+
+        return this;
+>this : T
+    }
+}
+
+const a = C.a();
+>a : typeof C
+>C.a() : typeof C
+>C.a : <T>(this: T) => T
+>C : typeof C
+>a : <T>(this: T) => T
+
+a; // typeof C
+>a : typeof C
+
+const c = new C();
+>c : C
+>new C() : C
+>C : typeof C
+
+const b = c.b();
+>b : C
+>c.b() : C
+>c.b : <T>(this: T) => T
+>c : C
+>b : <T>(this: T) => T
+
+b; // C
+>b : C
+

tests/baselines/reference/thisTag1.symbols

@@ -9,7 +9,7 @@ function f(s) {
 
     return this.n + s.length
 >this.n : Symbol(n, Decl(a.js, 0, 12))
->this : Symbol(__type, Decl(a.js, 0, 11))
+>this : Symbol(this)
 >n : Symbol(n, Decl(a.js, 0, 12))
 >s.length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
 >s : Symbol(s, Decl(a.js, 4, 11))

tests/cases/conformance/jsdoc/inferThis.ts

@@ -0,0 +1,31 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @filename: /a.js
+
+export class C {
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    static a() {
+        return this;
+    }
+
+    /**
+     * @template T
+     * @this {T}
+     * @return {T}
+     */
+    b() {
+        return this;
+    }
+}
+
+const a = C.a();
+a; // typeof C
+
+const c = new C();
+const b = c.b();
+b; // C