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[dev.typeparams] cmd/compile: simplify type alias handling for export

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Currently the exporter uses types.IsDotAlias(n.Sym()) to recognize
that n is a type alias, but IsDotAlias is actually meant for
recognizing aliases introduced by dot imports. Translated to go/types,
the current logic amounts recognizing type aliases as if by:

	var n *types.TypeName
	typ, ok := n.Pkg().Scope().Lookup(n.Name()).Type().(*types.Named)
	isAlias := !ok || typ.Obj().Pkg() != n.Pkg() || typ.Obj().Name() != n.Name()

But we can instead just check n.Alias() (eqv. n.IsAlias() in
go/types). In addition to being much simpler, this is also actually
correct for recognizing function-scoped type declarations (though we
don't currently support those anyway, nor would they go through this
exact code path).

To avoid possible future misuse of IsDotAlias, this CL also inlines
its trivial definition into its only call site.

Passes toolstash -cmp, also w/ -gcflags=all=-G=3.

Change-Id: I7c6283f4b58d5311aa683f8229bbf62f8bab2ff9
Reviewed-on: https://go-review.googlesource.com/c/go/+/320613
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Matthew Dempsky 2021-05-17 11:40:02 -07:00
parent 140cd7c1d3
commit f3fc8b5779
6 changed files with 4 additions and 18 deletions
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8
src/cmd/compile/internal/noder/decl.go
View file

@ -104,13 +104,7 @@ func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
if decl.Alias {
name, _ := g.def(decl.Name)
g.pragmaFlags(decl.Pragma, 0)
// TODO(mdempsky): This matches how typecheckdef marks aliases for
// export, but this won't generalize to exporting function-scoped
// type aliases. We should maybe just use n.Alias() instead.
if ir.CurFunc == nil {
name.Sym().Def = ir.TypeNode(name.Type())
}
assert(name.Alias()) // should be set by irgen.obj
out.Append(ir.NewDecl(g.pos(decl), ir.ODCLTYPE, name))
return