cmd/compile: remove skipping of implicit operations during export

We'll need to attach types to these operations, so we need to
represent them in the import/export data.

Some of the operations use a selector indicating a different package,
so we need to provide an option to encode the package of a selector.
The default selector() function can't encode that extra information,
as selector's exact encoding is used by go/types.

Change-Id: I4c110fe347b3d915f88a722834bc4058baea7854
Reviewed-on: https://go-review.googlesource.com/c/go/+/299771
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

src/cmd/compile/internal/typecheck/iexport.go

@@ -617,6 +617,11 @@ func (w *exportWriter) selector(s *types.Sym) {
 		base.Fatalf("missing currPkg")
 	}
 
+	// If the selector being written is unexported, it comes with a package qualifier.
+	// If the selector being written is exported, it is not package-qualified.
+	// See the spec: https://golang.org/ref/spec#Uniqueness_of_identifiers
+	// As an optimization, we don't actually write the package every time - instead we
+	// call setPkg before a group of selectors (all of which must have the same package qualifier).
 	pkg := w.currPkg
 	if types.IsExported(s.Name) {
 		pkg = types.LocalPkg
@@ -628,6 +633,26 @@ func (w *exportWriter) selector(s *types.Sym) {
 	w.string(s.Name)
 }
 
+// Export a selector, but one whose package may not match
+// the package being compiled. This is a separate function
+// because the standard selector() serialization format is fixed
+// by the go/types reader. This one can only be used during
+// inline/generic body exporting.
+func (w *exportWriter) exoticSelector(s *types.Sym) {
+	pkg := w.currPkg
+	if types.IsExported(s.Name) {
+		pkg = types.LocalPkg
+	}
+
+	w.string(s.Name)
+	if s.Pkg == pkg {
+		w.uint64(0)
+	} else {
+		w.uint64(1)
+		w.pkg(s.Pkg)
+	}
+}
+
 func (w *exportWriter) typ(t *types.Type) {
 	w.data.uint64(w.p.typOff(t))
 }
@@ -1299,21 +1324,6 @@ func simplifyForExport(n ir.Node) ir.Node {
 	case ir.OPAREN:
 		n := n.(*ir.ParenExpr)
 		return simplifyForExport(n.X)
-	case ir.ODEREF:
-		n := n.(*ir.StarExpr)
-		if n.Implicit() {
-			return simplifyForExport(n.X)
-		}
-	case ir.OADDR:
-		n := n.(*ir.AddrExpr)
-		if n.Implicit() {
-			return simplifyForExport(n.X)
-		}
-	case ir.ODOT, ir.ODOTPTR:
-		n := n.(*ir.SelectorExpr)
-		if n.Implicit() {
-			return simplifyForExport(n.X)
-		}
 	}
 	return n
 }
@@ -1437,7 +1447,7 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.op(ir.OXDOT)
 		w.pos(n.Pos())
 		w.expr(n.X)
-		w.selector(n.Sel)
+		w.exoticSelector(n.Sel)
 
 	case ir.ODOTTYPE, ir.ODOTTYPE2:
 		n := n.(*ir.TypeAssertExpr)

src/cmd/compile/internal/typecheck/iimport.go

@@ -466,6 +466,21 @@ func (r *importReader) ident(selector bool) *types.Sym {
 func (r *importReader) localIdent() *types.Sym { return r.ident(false) }
 func (r *importReader) selector() *types.Sym   { return r.ident(true) }
 
+func (r *importReader) exoticSelector() *types.Sym {
+	name := r.string()
+	if name == "" {
+		return nil
+	}
+	pkg := r.currPkg
+	if types.IsExported(name) {
+		pkg = types.LocalPkg
+	}
+	if r.uint64() != 0 {
+		pkg = r.pkg()
+	}
+	return pkg.Lookup(name)
+}
+
 func (r *importReader) qualifiedIdent() *ir.Ident {
 	name := r.string()
 	pkg := r.pkg()
@@ -753,7 +768,7 @@ func (r *importReader) doInline(fn *ir.Func) {
 		base.Fatalf("%v already has inline body", fn)
 	}
 
-	//fmt.Printf("Importing %v\n", n)
+	//fmt.Printf("Importing %s\n", fn.Nname.Sym().Name)
 	r.funcBody(fn)
 
 	importlist = append(importlist, fn)
@@ -1038,7 +1053,7 @@ func (r *importReader) node() ir.Node {
 
 	case ir.OXDOT:
 		// see parser.new_dotname
-		return ir.NewSelectorExpr(r.pos(), ir.OXDOT, r.expr(), r.selector())
+		return ir.NewSelectorExpr(r.pos(), ir.OXDOT, r.expr(), r.exoticSelector())
 
 	// case ODOTTYPE, ODOTTYPE2:
 	// 	unreachable - mapped to case ODOTTYPE below by exporter