go/gcimporter15: match https://golang.org/cl/21896/

Change-Id: I1cd7a77617658c057c863bd311470f1f22062aee
Reviewed-on: https://go-review.googlesource.com/21900
Reviewed-by: Alan Donovan <adonovan@google.com>

go/gcimporter15/bexport.go

@@ -91,10 +91,6 @@ func BExportData(pkg *types.Package) []byte {
 
 	// write package data
 	p.pkg(pkg, true)
-
-	// write compiler-specific flags
-	p.string("") // no flags to write in our case
-
 	if trace {
 		p.tracef("\n")
 	}

go/gcimporter15/bimport.go

@@ -82,9 +82,6 @@ func BImportData(imports map[string]*types.Package, data []byte, path string) (i
 		panic("imported packaged not found in pkgList[0]")
 	}
 
-	// read compiler-specific flags
-	p.string() // discard
-
 	// read objects of phase 1 only (see cmd/compiler/internal/gc/bexport.go)
 	objcount := 0
 	for {
@@ -197,7 +194,7 @@ func (p *importer) obj(tag int) {
 		p.declare(types.NewFunc(token.NoPos, pkg, name, sig))
 
 	default:
-		panic("unexpected object tag")
+		panic(fmt.Sprintf("unexpected object tag %d", tag))
 	}
 }
 
@@ -236,8 +233,7 @@ func (p *importer) typ(parent *types.Package) types.Type {
 	switch i {
 	case namedTag:
 		// read type object
-		name := p.string()
-		parent = p.pkg()
+		parent, name := p.qualifiedName()
 		scope := parent.Scope()
 		obj := scope.Lookup(name)
 
@@ -262,7 +258,7 @@ func (p *importer) typ(parent *types.Package) types.Type {
 		t0.SetUnderlying(p.typ(parent))
 
 		// interfaces don't have associated methods
-		if _, ok := t0.Underlying().(*types.Interface); ok {
+		if types.IsInterface(t0) {
 			return t
 		}