From: Matthew Dempsky <mdempsky@google.com>
Date: Thu, 12 May 2022 22:46:20 +0000 (-0700)
Subject: cmd/compile/internal/typecheck: remove iexport assumption of LocalPkg.Path == ""
X-Git-Tag: go1.19beta1~250
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=e3661d5f0820820d8d5e5e357244c95f788820e2;p=gostls13.git

cmd/compile/internal/typecheck: remove iexport assumption of LocalPkg.Path == ""

The indexed export data format encodes the local package's path as "",
because that's historically how we've represented it within
cmd/compile. The format also requires the local package to be first in
the exported list of packages, and was implicitly relying on ""
sorting before other, non-empty package paths.

We can't change the format without breaking existing importers (e.g.,
go/internal/gcimporter), but we can at least remove the dependency on
LocalPkg.Path being "".

Prep refactoring for CL 393715.

Updates #51734.

Change-Id: I6dd4eafd2d538f4e81376948ef9e92fc44a5462a
Reviewed-on: https://go-review.googlesource.com/c/go/+/406057
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>
---

diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index d6a7eade03..b12ddc9782 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -394,12 +394,15 @@ func (w *exportWriter) writeIndex(index map[*types.Sym]uint64, mainIndex bool) {
 		pkgs = append(pkgs, pkg)
 	}
 	sort.Slice(pkgs, func(i, j int) bool {
-		return pkgs[i].Path < pkgs[j].Path
+		return exportPath(pkgs[i]) < exportPath(pkgs[j])
 	})
+	if mainIndex {
+		base.Assertf(pkgs[0] == types.LocalPkg, "LocalPkg must be first")
+	}
 
 	w.uint64(uint64(len(pkgs)))
 	for _, pkg := range pkgs {
-		w.string(pkg.Path)
+		w.string(exportPath(pkg))
 		if mainIndex {
 			w.string(pkg.Name)
 			w.uint64(uint64(pkg.Height))
@@ -714,7 +717,18 @@ func (w *exportWriter) pkg(pkg *types.Pkg) {
 	// Ensure any referenced packages are declared in the main index.
 	w.p.allPkgs[pkg] = true
 
-	w.string(pkg.Path)
+	w.string(exportPath(pkg))
+}
+
+// exportPath returns the path for pkg as it appears in the iexport
+// file format. For historical reasons (before cmd/compile required
+// the -p flag), the local package is represented as the empty string,
+// instead of its actual path.
+func exportPath(pkg *types.Pkg) string {
+	if pkg == types.LocalPkg {
+		return ""
+	}
+	return pkg.Path
 }
 
 func (w *exportWriter) qualifiedIdent(n *ir.Name) {