issue6977.go

     1  // Copyright 2019 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 p
     6  
     7  import "io"
     8  
     9  // Alan's initial report.
    10  
    11  type I interface { f(); String() string }
    12  type J interface { g(); String() string }
    13  
    14  type IJ1 = interface { I; J }
    15  type IJ2 = interface { f(); g(); String() string }
    16  
    17  var _ = (*IJ1)(nil) == (*IJ2)(nil) // static assert that IJ1 and IJ2 are identical types
    18  
    19  // The canonical example.
    20  
    21  type ReadWriteCloser interface { io.ReadCloser; io.WriteCloser }
    22  
    23  // Some more cases.
    24  
    25  type M interface { m() }
    26  type M32 interface { m() int32 }
    27  type M64 interface { m() int64 }
    28  
    29  type U1 interface { m() }
    30  type U2 interface { m(); M }
    31  type U3 interface { M; m() }
    32  type U4 interface { M; M; M }
    33  type U5 interface { U1; U2; U3; U4 }
    34  
    35  type U6 interface { m(); m /* ERROR "duplicate method" */ () }
    36  type U7 interface { M32 /* ERROR "duplicate method" */ ; m() }
    37  type U8 interface { m(); M32 /* ERROR "duplicate method" */ }
    38  type U9 interface { M32; M64 /* ERROR "duplicate method" */ }
    39  
    40  // Verify that repeated embedding of the same interface(s)
    41  // eliminates duplicate methods early (rather than at the
    42  // end) to prevent exponential memory and time use.
    43  // Without early elimination, computing T29 may take dozens
    44  // of minutes.
    45  type (
    46          T0 interface { m() }
    47          T1 interface { T0; T0 }
    48          T2 interface { T1; T1 }
    49          T3 interface { T2; T2 }
    50          T4 interface { T3; T3 }
    51          T5 interface { T4; T4 }
    52          T6 interface { T5; T5 }
    53          T7 interface { T6; T6 }
    54          T8 interface { T7; T7 }
    55          T9 interface { T8; T8 }
    56  
    57          // TODO(gri) Enable this longer test once we have found a solution
    58          //           for the incorrect optimization in the validType check
    59          //           (see TODO in validtype.go).
    60          // T10 interface { T9; T9 }
    61          // T11 interface { T10; T10 }
    62          // T12 interface { T11; T11 }
    63          // T13 interface { T12; T12 }
    64          // T14 interface { T13; T13 }
    65          // T15 interface { T14; T14 }
    66          // T16 interface { T15; T15 }
    67          // T17 interface { T16; T16 }
    68          // T18 interface { T17; T17 }
    69          // T19 interface { T18; T18 }
    70  
    71          // T20 interface { T19; T19 }
    72          // T21 interface { T20; T20 }
    73          // T22 interface { T21; T21 }
    74          // T23 interface { T22; T22 }
    75          // T24 interface { T23; T23 }
    76          // T25 interface { T24; T24 }
    77          // T26 interface { T25; T25 }
    78          // T27 interface { T26; T26 }
    79          // T28 interface { T27; T27 }
    80          // T29 interface { T28; T28 }
    81  )
    82  
    83  // Verify that m is present.
    84  var x T9 // T29
    85  var _ = x.m
    86
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