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/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 {