|  | // errorcheck | 
|  |  | 
|  | // Copyright 2019 The Go Authors. All rights reserved. | 
|  | // Use of this source code is governed by a BSD-style | 
|  | // license that can be found in the LICENSE file. | 
|  |  | 
|  | package p | 
|  |  | 
|  | import "io" | 
|  |  | 
|  | // Alan's initial report. | 
|  |  | 
|  | type I interface { f(); String() string } | 
|  | type J interface { g(); String() string } | 
|  |  | 
|  | type IJ1 = interface { I; J } | 
|  | type IJ2 = interface { f(); g(); String() string } | 
|  |  | 
|  | var _ = (*IJ1)(nil) == (*IJ2)(nil) // static assert that IJ1 and IJ2 are identical types | 
|  |  | 
|  | // The canonical example. | 
|  |  | 
|  | type ReadWriteCloser interface { io.ReadCloser; io.WriteCloser } | 
|  |  | 
|  | // Some more cases. | 
|  |  | 
|  | type M interface { m() } | 
|  | type M32 interface { m() int32 } | 
|  | type M64 interface { m() int64 } | 
|  |  | 
|  | type U1 interface { m() } | 
|  | type U2 interface { m(); M } | 
|  | type U3 interface { M; m() } | 
|  | type U4 interface { M; M; M } | 
|  | type U5 interface { U1; U2; U3; U4 } | 
|  |  | 
|  | type U6 interface { m(); m() } // ERROR "duplicate method .*m" | 
|  | type U7 interface { M32; m() } // ERROR "duplicate method .*m" | 
|  | type U8 interface { m(); M32 } // ERROR "duplicate method .*m" | 
|  | type U9 interface { M32; M64 } // ERROR "duplicate method .*m" |