From 8ce35843de20ec7db259ef7e21e8f5bcbd5cec57 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Thu, 7 Aug 2014 12:45:28 -0700
Subject: [PATCH] go.tools/go/types: handle all receiver errors in go/types

Pending parser change in CL 123010044.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/125830043
---
 go/types/testdata/decls2a.src | 20 ++++++++++++++++----
 go/types/typexpr.go           | 25 +++++++++++++++++--------
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/go/types/testdata/decls2a.src b/go/types/testdata/decls2a.src
index 6fe0f27d..bdbecd9d 100644
--- a/go/types/testdata/decls2a.src
+++ b/go/types/testdata/decls2a.src
@@ -80,12 +80,24 @@ type T5 interface {
 func (T5 /* ERROR "invalid receiver" */ ) m1() {}
 func (T5 /* ERROR "invalid receiver" */ ) m2() {}
 
+// Methods associated with a named pointer type.
+type ptr *int
+func (ptr /* ERROR "invalid receiver" */ ) _() {}
+func (* /* ERROR "invalid receiver" */ ptr) _() {}
+
+// Methods with zero or multiple receivers.
+func ( /* ERROR "missing receiver" */ ) _() {}
+func (T3, * /* ERROR "exactly one receiver" */ T3) _() {}
+func (T3, T3, T3 /* ERROR "exactly one receiver" */ ) _() {}
+func (a, b /* ERROR "exactly one receiver" */ T3) _() {}
+func (a, b, c /* ERROR "exactly one receiver" */ T3) _() {}
+
 // Methods associated with non-local or unnamed types.
 func (int /* ERROR "invalid receiver" */ ) m() {}
-func ([ /* ERROR "identifier" */ ]int) m() {}
-func (time /* ERROR "identifier" */ .Time) m() {}
-func (*time /* ERROR "identifier" */ .Time) m() {}
-func (x interface /* ERROR "identifier" */ {}) m() {}
+func ([ /* ERROR "invalid receiver" */ ]int) m() {}
+func (time /* ERROR "invalid receiver" */ .Time) m() {}
+func (* /* ERROR "invalid receiver" */ time.Time) m() {}
+func (x /* ERROR "invalid receiver" */ interface{}) m() {}
 
 // Unsafe.Pointer is treated like a pointer when used as receiver type.
 type UP unsafe.Pointer
diff --git a/go/types/typexpr.go b/go/types/typexpr.go
index fa239ac0..b939bd20 100644
--- a/go/types/typexpr.go
+++ b/go/types/typexpr.go
@@ -139,21 +139,30 @@ func (check *Checker) typ(e ast.Expr) Type {
 }
 
 // funcType type-checks a function or method type and returns its signature.
-func (check *Checker) funcType(sig *Signature, recv *ast.FieldList, ftyp *ast.FuncType) *Signature {
+func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) *Signature {
 	scope := NewScope(check.scope, "function")
 	check.recordScope(ftyp, scope)
 
-	recv_, _ := check.collectParams(scope, recv, false)
+	recvList, _ := check.collectParams(scope, recvPar, false)
 	params, variadic := check.collectParams(scope, ftyp.Params, true)
 	results, _ := check.collectParams(scope, ftyp.Results, false)
 
-	if len(recv_) > 0 {
-		// There must be exactly one receiver.
-		if len(recv_) > 1 {
-			check.invalidAST(recv_[1].Pos(), "method must have exactly one receiver")
-			// ok to continue
+	if recvPar != nil {
+		// recv parameter list present (may be empty)
+		// spec: "The receiver is specified via an extra parameter section preceeding the
+		// method name. That parameter section must declare a single parameter, the receiver."
+		var recv *Var
+		switch len(recvList) {
+		case 0:
+			check.error(recvPar.Pos(), "method is missing receiver")
+			recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below
+		default:
+			// more than one receiver
+			check.error(recvList[len(recvList)-1].Pos(), "method must have exactly one receiver")
+			fallthrough // continue with first receiver
+		case 1:
+			recv = recvList[0]
 		}
-		recv := recv_[0]
 		// spec: "The receiver type must be of the form T or *T where T is a type name."
 		// (ignore invalid types - error was reported before)
 		if t, _ := deref(recv.typ); t != Typ[Invalid] {