[dev.typealias] cmd/compile: declare methods after resolving receiver type

For #18130.
Fixes #18655.

Change-Id: I58e2f076b9d8273f128cc033bba9edcd06c81567
Reviewed-on: https://go-review.googlesource.com/35575
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

7 files changed, 53 insertions, 32 deletions

diff --git a/src/cmd/compile/internal/gc/bimport.go b/src/cmd/compile/internal/gc/bimport.go
index 3c1f7100c3..1ee9e76737 100644
--- a/src/cmd/compile/internal/gc/bimport.go
+++ b/src/cmd/compile/internal/gc/bimport.go
@@ -466,14 +466,7 @@ func (p *importer) typ() *Type {
 			result := p.paramList()
 			nointerface := p.bool()
 
-			base := recv[0].Type
-			star := false
-			if base.IsPtr() {
-				base = base.Elem()
-				star = true
-			}
-
-			n := methodname0(sym, star, base.Sym)
+			n := newfuncname(methodname(sym, recv[0].Type))
 			n.Type = functypefield(recv[0], params, result)
 			checkwidth(n.Type)
 			addmethod(sym, n.Type, false, nointerface)
diff --git a/src/cmd/compile/internal/gc/dcl.go b/src/cmd/compile/internal/gc/dcl.go
index a5c50f06dc..856a7faced 100644
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -519,10 +519,6 @@ func funchdr(n *Node) {
 		Fatalf("funchdr: dclcontext = %d", dclcontext)
 	}
 
-	if Ctxt.Flag_dynlink && importpkg == nil && n.Func.Nname != nil {
-		makefuncsym(n.Func.Nname.Sym)
-	}
-
 	dclcontext = PAUTO
 	funcstart(n)
 
@@ -1163,19 +1159,19 @@ bad:
 	return nil
 }
 
-func methodname(s *Sym, recv *Node) *Node {
+// methodname is a misnomer because this now returns a Sym, rather
+// than an ONAME.
+// TODO(mdempsky): Reconcile with methodsym.
+func methodname(s *Sym, recv *Type) *Sym {
 	star := false
-	if recv.Op == OIND {
+	if recv.IsPtr() {
 		star = true
-		recv = recv.Left
+		recv = recv.Elem()
 	}
 
-	return methodname0(s, star, recv.Sym)
-}
-
-func methodname0(s *Sym, star bool, tsym *Sym) *Node {
+	tsym := recv.Sym
 	if tsym == nil || isblanksym(s) {
-		return newfuncname(s)
+		return s
 	}
 
 	var p string
@@ -1191,7 +1187,7 @@ func methodname0(s *Sym, star bool, tsym *Sym) *Node {
 		s = Pkglookup(p, tsym.Pkg)
 	}
 
-	return newfuncname(s)
+	return s
 }
 
 // Add a method, declared as a function.
@@ -1335,6 +1331,9 @@ func makefuncsym(s *Sym) {
 		return
 	}
 	s1 := funcsym(s)
+	if s1.Def != nil {
+		return
+	}
 	s1.Def = newfuncname(s1)
 	s1.Def.Func.Shortname = s
 	funcsyms = append(funcsyms, s1.Def)
diff --git a/src/cmd/compile/internal/gc/export.go b/src/cmd/compile/internal/gc/export.go
index 5556984dcb..58b2bf8121 100644
--- a/src/cmd/compile/internal/gc/export.go
+++ b/src/cmd/compile/internal/gc/export.go
@@ -83,7 +83,7 @@ func autoexport(n *Node, ctxt Class) {
 	if (ctxt != PEXTERN && ctxt != PFUNC) || dclcontext != PEXTERN {
 		return
 	}
-	if n.Name.Param != nil && n.Name.Param.Ntype != nil && n.Name.Param.Ntype.Op == OTFUNC && n.Name.Param.Ntype.Left != nil { // method
+	if n.Type != nil && n.Type.IsKind(TFUNC) && n.Type.Recv() != nil { // method
 		return
 	}
 
diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 0c5957f987..1d69151cc4 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -247,19 +247,19 @@ func (p *noder) funcHeader(fun *syntax.FuncDecl) *Node {
 				yyerror("func main must have no arguments and no return values")
 			}
 		}
-
-		f.Func.Nname = newfuncname(name)
 	} else {
-		// Receiver MethodName Signature
-
 		f.Func.Shortname = name
-		f.Func.Nname = methodname(f.Func.Shortname, t.Left.Right)
+		name = nblank.Sym // filled in by typecheckfunc
 	}
 
+	f.Func.Nname = newfuncname(name)
 	f.Func.Nname.Name.Defn = f
 	f.Func.Nname.Name.Param.Ntype = t // TODO: check if nname already has an ntype
 
-	declare(f.Func.Nname, PFUNC)
+	if fun.Recv == nil {
+		declare(f.Func.Nname, PFUNC)
+	}
+
 	funchdr(f)
 	return f
 }
diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index d751610763..1379bb56d4 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -3436,8 +3436,15 @@ func typecheckfunc(n *Node) {
 	t.SetNname(n.Func.Nname)
 	rcvr := t.Recv()
 	if rcvr != nil && n.Func.Shortname != nil {
+		n.Func.Nname.Sym = methodname(n.Func.Shortname, rcvr.Type)
+		declare(n.Func.Nname, PFUNC)
+
 		addmethod(n.Func.Shortname, t, true, n.Func.Pragma&Nointerface != 0)
 	}
+
+	if Ctxt.Flag_dynlink && importpkg == nil && n.Func.Nname != nil {
+		makefuncsym(n.Func.Nname.Sym)
+	}
 }
 
 // The result of stringtoarraylit MUST be assigned back to n, e.g.
diff --git a/test/alias2.go b/test/alias2.go
index 58eedf0c8c..32c3654995 100644
--- a/test/alias2.go
+++ b/test/alias2.go
@@ -37,8 +37,8 @@ type (
 // Methods can be declared on the original named type and the alias.
 func (T0) m1()  {} // GCCGO_ERROR "previous"
 func (*T0) m1() {} // ERROR "method redeclared: T0\.m1|redefinition of .m1."
-func (A0) m1()  {} // TODO(gri) this should be an error  // GCCGO_ERROR "redefinition of .m1."
-func (A0) m1()  {} // ERROR "A0\.m1 redeclared in this block|redefinition of .m1."
+func (A0) m1()  {} // ERROR "T0\.m1 redeclared in this block|redefinition of .m1."
+func (A0) m1()  {} // ERROR "T0\.m1 redeclared in this block|redefinition of .m1."
 func (A0) m2()  {}
 
 // Type aliases and the original type name can be used interchangeably.
@@ -95,10 +95,10 @@ type _ = reflect.ValueOf // ERROR "reflect.ValueOf is not a type|expected type"
 func (A1) m() {} // ERROR "cannot define new methods on non-local type int|may not define methods on non-local type"
 func (A2) m() {} // ERROR "invalid receiver type"
 func (A3) m() {} // ERROR "cannot define new methods on non-local type reflect.Value|may not define methods on non-local type"
-func (A4) m() {} // ERROR "cannot define new methods on non-local type reflect.Value|may not define methods on non-local type"
+func (A4) m() {} // ERROR "reflect.Value.m redeclared in this block" "cannot define new methods on non-local type reflect.Value|may not define methods on non-local type"
 
 type B1 = struct{}
 
-func (B1) m() {} // ERROR "invalid receiver type"
+func (B1) m() {} // ERROR "m redeclared in this block" "invalid receiver type"
 
 // TODO(gri) expand
diff --git a/test/fixedbugs/issue18655.go b/test/fixedbugs/issue18655.go
new file mode 100644
index 0000000000..abc2600280
--- /dev/null
+++ b/test/fixedbugs/issue18655.go
@@ -0,0 +1,22 @@
+// errorcheck
+
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T struct{}
+type A = T
+type B = T
+
+func (T) m() {}
+func (T) m() {} // ERROR "redeclared"
+func (A) m() {} // ERROR "redeclared"
+func (A) m() {} // ERROR "redeclared"
+func (B) m() {} // ERROR "redeclared"
+func (B) m() {} // ERROR "redeclared"
+
+func (*T) m() {} // ERROR "redeclared"
+func (*A) m() {} // ERROR "redeclared"
+func (*B) m() {} // ERROR "redeclared"