Add regression test

tests/baselines/reference/baseExpressionTypeParameters.errors.txt

@@ -0,0 +1,19 @@
+tests/cases/compiler/baseExpressionTypeParameters.ts(10,27): error TS2561: Base class expressions cannot reference class type parameters.
+
+
+==== tests/cases/compiler/baseExpressionTypeParameters.ts (1 errors) ====
+    // Repro from #17829
+    
+    function base<T>() {
+        class Base {
+            static prop: T;
+        }
+        return Base;
+    }
+    
+    class Gen<T> extends base<T>() {}  // Error, T not in scope
+                              ~
+!!! error TS2561: Base class expressions cannot reference class type parameters.
+    class Spec extends Gen<string> {}
+    
+    <string>Spec.prop;

tests/baselines/reference/baseExpressionTypeParameters.js

@@ -0,0 +1,50 @@
+//// [baseExpressionTypeParameters.ts]
+// Repro from #17829
+
+function base<T>() {
+    class Base {
+        static prop: T;
+    }
+    return Base;
+}
+
+class Gen<T> extends base<T>() {}  // Error, T not in scope
+class Spec extends Gen<string> {}
+
+<string>Spec.prop;
+
+//// [baseExpressionTypeParameters.js]
+// Repro from #17829
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = Object.setPrototypeOf ||
+        ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+        function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+function base() {
+    var Base = /** @class */ (function () {
+        function Base() {
+        }
+        return Base;
+    }());
+    return Base;
+}
+var Gen = /** @class */ (function (_super) {
+    __extends(Gen, _super);
+    function Gen() {
+        return _super !== null && _super.apply(this, arguments) || this;
+    }
+    return Gen;
+}(base())); // Error, T not in scope
+var Spec = /** @class */ (function (_super) {
+    __extends(Spec, _super);
+    function Spec() {
+        return _super !== null && _super.apply(this, arguments) || this;
+    }
+    return Spec;
+}(Gen));
+Spec.prop;

tests/cases/compiler/baseExpressionTypeParameters.ts

@@ -0,0 +1,13 @@
+// Repro from #17829
+
+function base<T>() {
+    class Base {
+        static prop: T;
+    }
+    return Base;
+}
+
+class Gen<T> extends base<T>() {}  // Error, T not in scope
+class Spec extends Gen<string> {}
+
+<string>Spec.prop;