cmd/compile: simplify exportsym flags and logic

We used to have three Sym flags for dealing with export/reexport:
Export, Package, and Exported.

Export and Package were used to distinguish whether a symbol is
exported or package-scope (i.e., mutually exclusive), except that for
local declarations Export served double-duty as tracking whether the
symbol had been added to exportlist.

Meanwhile, imported declarations that needed reexporting could be
added to exportlist multiple times, necessitating a flag to track
whether they'd already been written out by exporter.

Simplify all of these into a single OnExportList flag so that we can
ensure symbols on exportlist are present exactly once. Merge
reexportsym into exportsym so there's a single place where we append
to exportlist.

Code that used to set Exported to prevent a symbol from being exported
can now just set OnExportList before calling declare to prevent it
from even appearing on exportlist.

Lastly, drop the IsAlias check in exportsym: we call exportsym too
early for local symbols to detect if they're an alias, and we never
reexport aliases.

Passes toolstash-check.

Change-Id: Icdea3719105dc169fcd7651606589cd08b0a80ff
Reviewed-on: https://go-review.googlesource.com/103865
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 11 insertions, 17 deletions

diff --git a/src/cmd/compile/internal/types/sym.go b/src/cmd/compile/internal/types/sym.go
index 1b9d01dab5..00328fa44f 100644
--- a/src/cmd/compile/internal/types/sym.go
+++ b/src/cmd/compile/internal/types/sym.go
@@ -35,30 +35,24 @@ type Sym struct {
 }
 
 const (
-	symExport = 1 << iota // added to exportlist (no need to add again)
-	symPackage
-	symExported // already written out by export
+	symOnExportList = 1 << iota // added to exportlist (no need to add again)
 	symUniq
 	symSiggen
 	symAsm
 	symAlgGen
 )
 
-func (sym *Sym) Export() bool   { return sym.flags&symExport != 0 }
-func (sym *Sym) Package() bool  { return sym.flags&symPackage != 0 }
-func (sym *Sym) Exported() bool { return sym.flags&symExported != 0 }
-func (sym *Sym) Uniq() bool     { return sym.flags&symUniq != 0 }
-func (sym *Sym) Siggen() bool   { return sym.flags&symSiggen != 0 }
-func (sym *Sym) Asm() bool      { return sym.flags&symAsm != 0 }
-func (sym *Sym) AlgGen() bool   { return sym.flags&symAlgGen != 0 }
+func (sym *Sym) OnExportList() bool { return sym.flags&symOnExportList != 0 }
+func (sym *Sym) Uniq() bool         { return sym.flags&symUniq != 0 }
+func (sym *Sym) Siggen() bool       { return sym.flags&symSiggen != 0 }
+func (sym *Sym) Asm() bool          { return sym.flags&symAsm != 0 }
+func (sym *Sym) AlgGen() bool       { return sym.flags&symAlgGen != 0 }
 
-func (sym *Sym) SetExport(b bool)   { sym.flags.set(symExport, b) }
-func (sym *Sym) SetPackage(b bool)  { sym.flags.set(symPackage, b) }
-func (sym *Sym) SetExported(b bool) { sym.flags.set(symExported, b) }
-func (sym *Sym) SetUniq(b bool)     { sym.flags.set(symUniq, b) }
-func (sym *Sym) SetSiggen(b bool)   { sym.flags.set(symSiggen, b) }
-func (sym *Sym) SetAsm(b bool)      { sym.flags.set(symAsm, b) }
-func (sym *Sym) SetAlgGen(b bool)   { sym.flags.set(symAlgGen, b) }
+func (sym *Sym) SetOnExportList(b bool) { sym.flags.set(symOnExportList, b) }
+func (sym *Sym) SetUniq(b bool)         { sym.flags.set(symUniq, b) }
+func (sym *Sym) SetSiggen(b bool)       { sym.flags.set(symSiggen, b) }
+func (sym *Sym) SetAsm(b bool)          { sym.flags.set(symAsm, b) }
+func (sym *Sym) SetAlgGen(b bool)       { sym.flags.set(symAlgGen, b) }
 
 func (sym *Sym) IsBlank() bool {
 	return sym != nil && sym.Name == "_"