b.go

     1  // Copyright 2022 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 (
    10  	lA[P any]               [10]P
    11  	lS[P any]               struct{ f P }
    12  	lP[P any]               *P
    13  	lM[K comparable, V any] map[K]V
    14  )
    15  
    16  // local cycles
    17  type (
    18  	A  lA[A]            // ERROR "invalid recursive type"
    19  	S  lS[S]            // ERROR "invalid recursive type"
    20  	P  lP[P]            // ok (indirection through lP)
    21  	M1 lM[int, M1]      // ok (indirection through lM)
    22  	M2 lM[lA[byte], M2] // ok (indirection through lM)
    23  
    24  	A2 lA[lS[lP[A2]]] // ok (indirection through lP)
    25  	A3 lA[lS[lS[A3]]] // ERROR "invalid recursive type"
    26  )
    27  
    28  // cycles through imported types
    29  type (
    30  	Ai  a.A[Ai]             // ERROR "invalid recursive type"
    31  	Si  a.S[Si]             // ERROR "invalid recursive type"
    32  	Pi  a.P[Pi]             // ok (indirection through a.P)
    33  	M1i a.M[int, M1i]       // ok (indirection through a.M)
    34  	M2i a.M[a.A[byte], M2i] // ok (indirection through a.M)
    35  
    36  	A2i a.A[a.S[a.P[A2i]]] // ok (indirection through a.P)
    37  	A3i a.A[a.S[a.S[A3i]]] // ERROR "invalid recursive type"
    38  
    39  	T2 a.S[T0[T2]] // ERROR "invalid recursive type"
    40  	T3 T0[Ai]      // no follow-on error here
    41  )
    42  
    43  // test case from issue
    44  
    45  type T0[P any] struct {
    46  	f P
    47  }
    48  
    49  type T1 struct { // ERROR "invalid recursive type"
    50  	_ T0[T1]
    51  }
    52
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