From 6971090515bab8d4ecf19933736591904f8287bc Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Mon, 5 Nov 2018 15:51:11 -0800 Subject: [PATCH] [release-branch.go1.11] go/types: avoid certain problems with recursive alias type declarations It is possible to create certain recursive type declarations involving alias types which cause the type-checker to produce an (invalid) type for the alias because it is not yet available. By type-checking alias declarations in a 2nd phase, the problem is mitigated a bit since it requires more convoluted alias declarations for the problem to appear. Also re-enable testing of fixedbugs/issue27232.go again (which was the original cause for this change). Updates #28576. Fixes #28972. Change-Id: If6f9656a95262e6575b01c4a003094d41551564b Reviewed-on: https://go-review.googlesource.com/c/147597 Reviewed-by: Alan Donovan Reviewed-on: https://go-review.googlesource.com/c/151500 Run-TryBot: Andrew Bonventre TryBot-Result: Gobot Gobot Reviewed-by: Andrew Bonventre --- src/go/types/resolver.go | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/src/go/types/resolver.go b/src/go/types/resolver.go index 5cbaba187b..6646711e7f 100644 --- a/src/go/types/resolver.go +++ b/src/go/types/resolver.go @@ -538,7 +538,25 @@ func (check *Checker) packageObjects() { // pre-allocate space for type declaration paths so that the underlying array is reused typePath := make([]*TypeName, 0, 8) + // We process non-alias declarations first, in order to avoid situations where + // the type of an alias declaration is needed before it is available. In general + // this is still not enough, as it is possible to create sufficiently convoluted + // recursive type definitions that will cause a type alias to be needed before it + // is available (see issue #25838 for examples). + // As an aside, the cmd/compiler suffers from the same problem (#25838). + var aliasList []*TypeName + // phase 1 for _, obj := range objList { + // If we have a type alias, collect it for the 2nd phase. + if tname, _ := obj.(*TypeName); tname != nil && check.objMap[tname].alias { + aliasList = append(aliasList, tname) + continue + } + + check.objDecl(obj, nil, typePath) + } + // phase 2 + for _, obj := range aliasList { check.objDecl(obj, nil, typePath) } -- 2.48.1