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go/test/fixedbugs/issue18640.go
Robert Griesemer 48987baa09 cmd/compile: correct alias cycle detection
The original fix (https://go-review.googlesource.com/c/go/+/35831)
for this issue was incorrect as it reported cycles in cases where
it shouldn't.

Instead, use a different approach: A type cycle containing aliases
is only a cycle if there are no type definitions. As soon as there
is a type definition, alias expansion terminates and there is no
cycle.

Approach: Split sprint_depchain into two non-recursive and more
easily understandable functions (cycleFor and cycleTrace),
and use those instead for cycle reporting. Analyze the cycle
returned by cycleFor before issueing an alias cycle error.

Also: Removed original fix (main.go) which introduced a separate
crash (#23823).

Fixes #18640.
Fixes #23823.
Fixes #24939.

Change-Id: Ic3707a9dec40a71dc928a3e49b4868c5fac3d3b7
Reviewed-on: https://go-review.googlesource.com/118078
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2018-06-12 18:55:39 +00:00

48 lines
554 B
Go

// compile
// Copyright 2017 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
type (
a = b
b struct {
*a
}
)
type (
c struct {
*d
}
d = c
)
// The compiler reports an incorrect (non-alias related)
// type cycle here (via dowith()). Disabled for now.
// See issue #25838.
/*
type (
e = f
f = g
g = []h
h i
i = j
j = e
)
*/
type (
a1 struct{ *b1 }
b1 = c1
c1 struct{ *b1 }
)
type (
a2 struct{ b2 }
b2 = c2
c2 struct{ *b2 }
)