cmd/compile: remove structpkg global variable

The structpkg global variable was only used to verify internal
consistency when declaring methods during import. Track the
value in the parser and binary importer directly and pass it
to the relevant function as an argument.

Change-Id: I7e5e006f9046d84f9a3959616f073798fda36c97
Reviewed-on: https://go-review.googlesource.com/20606
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/bimport.go

@@ -195,7 +195,6 @@ func (p *importer) localname() *Sym {
 	if name == "" {
 		Fatalf("importer: unexpected anonymous name")
 	}
-	structpkg = importpkg // parser.go:hidden_pkg_importsym
 	return importpkg.Lookup(name)
 }
 
@@ -252,13 +251,7 @@ func (p *importer) typ() *Type {
 			n := methodname1(newname(sym), recv[0].Right)
 			n.Type = functype(recv[0], params, result)
 			checkwidth(n.Type)
-			// addmethod uses the global variable structpkg to verify consistency
-			{
-				saved := structpkg
-				structpkg = tsym.Pkg
-				addmethod(sym, n.Type, false, false)
-				structpkg = saved
-			}
+			addmethod(sym, n.Type, tsym.Pkg, false, false)
 			funchdr(n)
 
 			// (comment from parser.go)

src/cmd/compile/internal/gc/dcl.go

@@ -1284,11 +1284,13 @@ func methodname1(n *Node, t *Node) *Node {
 	return n
 }
 
-// add a method, declared as a function,
-// n is fieldname, pa is base type, t is function type
-func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
+// Add a method, declared as a function.
+// - msym is the method symbol
+// - t is function type (with receiver)
+// - tpkg is the package of the type declaring the method during import, or nil (ignored) --- for verification only
+func addmethod(msym *Sym, t *Type, tpkg *Pkg, local, nointerface bool) {
 	// get field sym
-	if sf == nil {
+	if msym == nil {
 		Fatalf("no method symbol")
 	}
 
@@ -1299,7 +1301,7 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 		return
 	}
 
-	pa = pa.Type
+	pa = pa.Type // base type
 	f := methtype(pa, 1)
 	if f == nil {
 		t = pa
@@ -1348,20 +1350,20 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 		return
 	}
 
-	if isblanksym(sf) {
+	if isblanksym(msym) {
 		return
 	}
 
 	if pa.Etype == TSTRUCT {
 		for f, it := IterFields(pa); f != nil; f = it.Next() {
-			if f.Sym == sf {
-				Yyerror("type %v has both field and method named %v", pa, sf)
+			if f.Sym == msym {
+				Yyerror("type %v has both field and method named %v", pa, msym)
 				return
 			}
 		}
 	}
 
-	n := Nod(ODCLFIELD, newname(sf), nil)
+	n := Nod(ODCLFIELD, newname(msym), nil)
 	n.Type = t
 
 	var d *Type // last found
@@ -1370,11 +1372,11 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 		if f.Etype != TFIELD {
 			Fatalf("addmethod: not TFIELD: %v", Tconv(f, obj.FmtLong))
 		}
-		if sf.Name != f.Sym.Name {
+		if msym.Name != f.Sym.Name {
 			continue
 		}
 		if !Eqtype(t, f.Type) {
-			Yyerror("method redeclared: %v.%v\n\t%v\n\t%v", pa, sf, f.Type, t)
+			Yyerror("method redeclared: %v.%v\n\t%v\n\t%v", pa, msym, f.Type, t)
 		}
 		return
 	}
@@ -1383,8 +1385,8 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 	f.Nointerface = nointerface
 
 	// during import unexported method names should be in the type's package
-	if importpkg != nil && f.Sym != nil && !exportname(f.Sym.Name) && f.Sym.Pkg != structpkg {
-		Fatalf("imported method name %v in wrong package %s\n", Sconv(f.Sym, obj.FmtSign), structpkg.Name)
+	if tpkg != nil && f.Sym != nil && !exportname(f.Sym.Name) && f.Sym.Pkg != tpkg {
+		Fatalf("imported method name %v in wrong package %s\n", Sconv(f.Sym, obj.FmtSign), tpkg.Name)
 	}
 
 	if d == nil {
@@ -1392,7 +1394,6 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 	} else {
 		d.Down = f
 	}
-	return
 }
 
 func funccompile(n *Node) {

src/cmd/compile/internal/gc/go.go

@@ -248,8 +248,6 @@ var localpkg *Pkg // package being compiled
 
 var importpkg *Pkg // package being imported
 
-var structpkg *Pkg // package that declared struct, during import
-
 var gostringpkg *Pkg // fake pkg for Go strings
 
 var itabpkg *Pkg // fake pkg for itab cache

src/cmd/compile/internal/gc/parser.go

@@ -36,6 +36,9 @@ type parser struct {
 	fnest  int    // function nesting level (for error handling)
 	xnest  int    // expression nesting level (for complit ambiguity resolution)
 	indent []byte // tracing support
+
+	// TODO(gri) remove this once we switch to binary export format
+	structpkg *Pkg // for verification in addmethod only
 }
 
 // newparser returns a new parser ready to parse from src.
@@ -2008,7 +2011,7 @@ func (p *parser) hidden_fndcl() *Node {
 		ss.Type = functype(s2[0], s6, s8)
 
 		checkwidth(ss.Type)
-		addmethod(s4, ss.Type, false, false)
+		addmethod(s4, ss.Type, p.structpkg, false, false)
 		funchdr(ss)
 
 		// inl.C's inlnode in on a dotmeth node expects to find the inlineable body as
@@ -2863,12 +2866,9 @@ func (p *parser) hidden_pkg_importsym() *Sym {
 		defer p.trace("hidden_pkg_importsym")()
 	}
 
-	s1 := p.hidden_importsym()
-
-	ss := s1
-	structpkg = ss.Pkg
-
-	return ss
+	s := p.hidden_importsym()
+	p.structpkg = s.Pkg
+	return s
 }
 
 func (p *parser) hidden_pkgtype() *Type {

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

@@ -3438,7 +3438,7 @@ func typecheckfunc(n *Node) {
 	t.Nname = n.Func.Nname
 	rcvr := t.Recv()
 	if rcvr != nil && n.Func.Shortname != nil {
-		addmethod(n.Func.Shortname.Sym, t, true, n.Func.Nname.Nointerface)
+		addmethod(n.Func.Shortname.Sym, t, nil, true, n.Func.Nname.Nointerface)
 	}
 
 	for _, ln := range n.Func.Dcl {