[dev.typeparams] cmd/compile/internal/types2: implement package height

This CL extends types2 with package height information, styled after
the way it works already in cmd/compile:

- A new NewPackageHeight entry point for constructing packages with
  explicit height information, and a corresponding Height accessor
  method.

- The types2 importer is updated to provide package height for
  imported packages.

- The types2 type checker sets height based on imported packages.

- Adds an assertion to irgen to verify that types1 and types2
  calculated the same height for the source package.

- Func.less's ordering incorporates package height to match
  types.Sym.less and is generalized to object.less.

- sortTypes (used for sorting embedded types) now sorts defined types
  using object.less as well.

Change-Id: Id4dbbb627aef405cc7438d611cbdd5a5bd97fc96
Reviewed-on: https://go-review.googlesource.com/c/go/+/321231
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/importer/iimport.go b/src/cmd/compile/internal/importer/iimport.go
index 5c02f837ef..b91b209d35 100644
--- a/src/cmd/compile/internal/importer/iimport.go
+++ b/src/cmd/compile/internal/importer/iimport.go
@@ -118,17 +118,22 @@ func iImportData(imports map[string]*types2.Package, data []byte, path string) (
 		pkgPathOff := r.uint64()
 		pkgPath := p.stringAt(pkgPathOff)
 		pkgName := p.stringAt(r.uint64())
-		_ = r.uint64() // package height; unused by go/types
+		pkgHeight := int(r.uint64())
 
 		if pkgPath == "" {
 			pkgPath = path
 		}
 		pkg := imports[pkgPath]
 		if pkg == nil {
-			pkg = types2.NewPackage(pkgPath, pkgName)
+			pkg = types2.NewPackageHeight(pkgPath, pkgName, pkgHeight)
 			imports[pkgPath] = pkg
-		} else if pkg.Name() != pkgName {
-			errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
+		} else {
+			if pkg.Name() != pkgName {
+				errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
+			}
+			if pkg.Height() != pkgHeight {
+				errorf("conflicting heights %v and %v for package %q", pkg.Height(), pkgHeight, path)
+			}
 		}
 
 		p.pkgCache[pkgPathOff] = pkg