==== tests/cases/compiler/ambientExternalModuleReopen.ts (2 errors) ====
    declare module "fs" {
        var x: string;
    }
    declare module 'fs' {
                   ~~~~
!!! ambientExternalModuleReopen.ts(4,16): error TS2000: Duplicate identifier ''fs''. Additional locations:
!!! 	ambientExternalModuleReopen.ts(1,16)
                   ~~~~
!!! ambientExternalModuleReopen.ts(4,16): error TS2191: Ambient external module declaration cannot be reopened.
        var y: number;
    }