tests/cases/compiler/collisionThisExpressionAndAmbientVarInGlobal.ts(3,1): error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference. ==== tests/cases/compiler/collisionThisExpressionAndAmbientVarInGlobal.ts (1 errors) ==== declare var _this: number; // no error as no code gen var f = () => this; _this = 10; // Error ~~~~~ !!! error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.