b.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package b
     6  
     7  import "./a"
     8  
     9  type T struct{ a.T }
    10  
    11  func (T) m() { println("ok") }
    12  
    13  // The compiler used to not pay attention to package for non-exported
    14  // methods when statically constructing itabs. The consequence of this
    15  // was that the call to b.F1(b.T{}) in c.go would create an itab using
    16  // a.T.m instead of b.T.m.
    17  func F1(i interface{ m() }) { i.m() }
    18  
    19  // The interface method calling convention depends on interface method
    20  // sets being sorted in the same order across compilation units.  In
    21  // the test case below, at the call to b.F2(b.T{}) in c.go, the
    22  // interface method set is sorted as { a.m(); b.m() }.
    23  //
    24  // However, while compiling package b, its package path is set to "",
    25  // so the code produced for F2 uses { b.m(); a.m() } as the method set
    26  // order. So again, it ends up calling the wrong method.
    27  //
    28  // Also, this function is marked noinline because it's critical to the
    29  // test that the interface method call happen in this compilation
    30  // unit, and the itab construction happens in c.go.
    31  //
    32  //go:noinline
    33  func F2(i interface {
    34  	m()
    35  	a.I // embeds m() from package a
    36  }) {
    37  	i.m()
    38  }
    39
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