[dev.regabi] cmd/compile: merge {Selector,CallPart,Method}Expr

These three expression nodes all represent the same syntax, and so
they're represented the same within types2. And also they're not
handled that meaningfully differently throughout the rest of the
compiler to merit unique representations.

Method expressions are somewhat unique today that they're very
frequently turned into plain function names. But eventually that can
be handled by a post-typecheck desugaring phase that reduces the
number of redundant AST forms.

Passes toolstash -cmp.

Change-Id: I20df91bbd0d885c1f18ec67feb61ae1558670719
Reviewed-on: https://go-review.googlesource.com/c/go/+/280636
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

14 files changed, 58 insertions, 154 deletions

diff --git a/src/cmd/compile/internal/escape/escape.go b/src/cmd/compile/internal/escape/escape.go
index d8f0111d2d..7b4037e028 100644
--- a/src/cmd/compile/internal/escape/escape.go
+++ b/src/cmd/compile/internal/escape/escape.go
@@ -612,10 +612,10 @@ func (e *escape) exprSkipInit(k hole, n ir.Node) {
 		// Flow the receiver argument to both the closure and
 		// to the receiver parameter.
 
-		n := n.(*ir.CallPartExpr)
+		n := n.(*ir.SelectorExpr)
 		closureK := e.spill(k, n)
 
-		m := n.Method
+		m := n.Selection
 
 		// We don't know how the method value will be called
 		// later, so conservatively assume the result
@@ -1542,7 +1542,7 @@ func (e *escape) finish(fns []*ir.Func) {
 					n := n.(*ir.ClosureExpr)
 					n.SetTransient(true)
 				case ir.OCALLPART:
-					n := n.(*ir.CallPartExpr)
+					n := n.(*ir.SelectorExpr)
 					n.SetTransient(true)
 				case ir.OSLICELIT:
 					n := n.(*ir.CompLitExpr)
@@ -1863,7 +1863,7 @@ func HeapAllocReason(n ir.Node) string {
 	if n.Op() == ir.OCLOSURE && typecheck.ClosureType(n.(*ir.ClosureExpr)).Size() >= ir.MaxImplicitStackVarSize {
 		return "too large for stack"
 	}
-	if n.Op() == ir.OCALLPART && typecheck.PartialCallType(n.(*ir.CallPartExpr)).Size() >= ir.MaxImplicitStackVarSize {
+	if n.Op() == ir.OCALLPART && typecheck.PartialCallType(n.(*ir.SelectorExpr)).Size() >= ir.MaxImplicitStackVarSize {
 		return "too large for stack"
 	}
 
diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index 67162771e9..fc6a17b933 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -419,6 +419,9 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 
 	case ir.OCALLPART, ir.OSLICELIT:
 		v.budget-- // Hack for toolstash -cmp.
+
+	case ir.OMETHEXPR:
+		v.budget++ // Hack for toolstash -cmp.
 	}
 
 	v.budget--
@@ -613,12 +616,12 @@ func inlCallee(fn ir.Node) *ir.Func {
 	fn = ir.StaticValue(fn)
 	switch fn.Op() {
 	case ir.OMETHEXPR:
-		fn := fn.(*ir.MethodExpr)
+		fn := fn.(*ir.SelectorExpr)
 		n := ir.MethodExprName(fn)
-		// Check that receiver type matches fn.Left.
+		// Check that receiver type matches fn.X.
 		// TODO(mdempsky): Handle implicit dereference
 		// of pointer receiver argument?
-		if n == nil || !types.Identical(n.Type().Recv().Type, fn.T) {
+		if n == nil || !types.Identical(n.Type().Recv().Type, fn.X.Type()) {
 			return nil
 		}
 		return n.Func
@@ -1098,7 +1101,7 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 		return n
 
 	case ir.OMETHEXPR:
-		n := n.(*ir.MethodExpr)
+		n := n.(*ir.SelectorExpr)
 		return n
 
 	case ir.OLITERAL, ir.ONIL, ir.OTYPE:
diff --git a/src/cmd/compile/internal/ir/expr.go b/src/cmd/compile/internal/ir/expr.go
index 1337d356a1..872f81a447 100644
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@@ -225,26 +225,6 @@ func (n *CallExpr) SetOp(op Op) {
 	}
 }
 
-// A CallPartExpr is a method expression X.Method (uncalled).
-type CallPartExpr struct {
-	miniExpr
-	Func     *Func
-	X        Node
-	Method   *types.Field
-	Prealloc *Name
-}
-
-func NewCallPartExpr(pos src.XPos, x Node, method *types.Field, fn *Func) *CallPartExpr {
-	n := &CallPartExpr{Func: fn, X: x, Method: method}
-	n.op = OCALLPART
-	n.pos = pos
-	n.typ = fn.Type()
-	n.Func = fn
-	return n
-}
-
-func (n *CallPartExpr) Sym() *types.Sym { return n.Method.Sym }
-
 // A ClosureExpr is a function literal expression.
 type ClosureExpr struct {
 	miniExpr
@@ -476,24 +456,6 @@ func (n *MakeExpr) SetOp(op Op) {
 	}
 }
 
-// A MethodExpr is a method expression T.M (where T is a type).
-type MethodExpr struct {
-	miniExpr
-	T         *types.Type
-	Method    *types.Field
-	FuncName_ *Name
-}
-
-func NewMethodExpr(pos src.XPos, t *types.Type, method *types.Field) *MethodExpr {
-	n := &MethodExpr{T: t, Method: method}
-	n.pos = pos
-	n.op = OMETHEXPR
-	return n
-}
-
-func (n *MethodExpr) FuncName() *Name { return n.FuncName_ }
-func (n *MethodExpr) Sym() *types.Sym { panic("MethodExpr.Sym") }
-
 // A NilExpr represents the predefined untyped constant nil.
 // (It may be copied and assigned a type, though.)
 type NilExpr struct {
@@ -567,12 +529,13 @@ func NewNameOffsetExpr(pos src.XPos, name *Name, offset int64, typ *types.Type)
 	return n
 }
 
-// A SelectorExpr is a selector expression X.Sym.
+// A SelectorExpr is a selector expression X.Sel.
 type SelectorExpr struct {
 	miniExpr
 	X         Node
 	Sel       *types.Sym
 	Selection *types.Field
+	Prealloc  *Name // preallocated storage for OCALLPART, if any
 }
 
 func NewSelectorExpr(pos src.XPos, op Op, x Node, sel *types.Sym) *SelectorExpr {
@@ -586,7 +549,7 @@ func (n *SelectorExpr) SetOp(op Op) {
 	switch op {
 	default:
 		panic(n.no("SetOp " + op.String()))
-	case ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OXDOT:
+	case OXDOT, ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OCALLPART, OMETHEXPR:
 		n.op = op
 	}
 }
@@ -596,6 +559,16 @@ func (n *SelectorExpr) Implicit() bool     { return n.flags&miniExprImplicit !=
 func (n *SelectorExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 func (n *SelectorExpr) Offset() int64      { return n.Selection.Offset }
 
+func (n *SelectorExpr) FuncName() *Name {
+	if n.Op() != OMETHEXPR {
+		panic(n.no("FuncName"))
+	}
+	fn := NewNameAt(n.Selection.Pos, MethodSym(n.X.Type(), n.Sel))
+	fn.Class_ = PFUNC
+	fn.SetType(n.Type())
+	return fn
+}
+
 // Before type-checking, bytes.Buffer is a SelectorExpr.
 // After type-checking it becomes a Name.
 func (*SelectorExpr) CanBeNtype() {}
@@ -1089,13 +1062,8 @@ func MethodExprName(n Node) *Name {
 // MethodFunc is like MethodName, but returns the types.Field instead.
 func MethodExprFunc(n Node) *types.Field {
 	switch n.Op() {
-	case ODOTMETH:
+	case ODOTMETH, OMETHEXPR, OCALLPART:
 		return n.(*SelectorExpr).Selection
-	case OMETHEXPR:
-		return n.(*MethodExpr).Method
-	case OCALLPART:
-		n := n.(*CallPartExpr)
-		return n.Method
 	}
 	base.Fatalf("unexpected node: %v (%v)", n, n.Op())
 	panic("unreachable")
diff --git a/src/cmd/compile/internal/ir/fmt.go b/src/cmd/compile/internal/ir/fmt.go
index 49f451a5d8..7680f05ad2 100644
--- a/src/cmd/compile/internal/ir/fmt.go
+++ b/src/cmd/compile/internal/ir/fmt.go
@@ -630,10 +630,6 @@ func exprFmt(n Node, s fmt.State, prec int) {
 	case OPACK, ONONAME:
 		fmt.Fprint(s, n.Sym())
 
-	case OMETHEXPR:
-		n := n.(*MethodExpr)
-		fmt.Fprint(s, n.FuncName().Sym())
-
 	case ONAMEOFFSET:
 		n := n.(*NameOffsetExpr)
 		fmt.Fprintf(s, "(%v)(%v@%d)", n.Type(), n.Name_, n.Offset_)
@@ -749,16 +745,7 @@ func exprFmt(n Node, s fmt.State, prec int) {
 		n := n.(*StructKeyExpr)
 		fmt.Fprintf(s, "%v:%v", n.Field, n.Value)
 
-	case OCALLPART:
-		n := n.(*CallPartExpr)
-		exprFmt(n.X, s, nprec)
-		if n.Method.Sym == nil {
-			fmt.Fprint(s, ".<nil>")
-			return
-		}
-		fmt.Fprintf(s, ".%s", n.Method.Sym.Name)
-
-	case OXDOT, ODOT, ODOTPTR, ODOTINTER, ODOTMETH:
+	case OXDOT, ODOT, ODOTPTR, ODOTINTER, ODOTMETH, OCALLPART, OMETHEXPR:
 		n := n.(*SelectorExpr)
 		exprFmt(n.X, s, nprec)
 		if n.Sel == nil {
@@ -1160,12 +1147,6 @@ func dumpNode(w io.Writer, n Node, depth int) {
 		}
 		return
 
-	case OMETHEXPR:
-		n := n.(*MethodExpr)
-		fmt.Fprintf(w, "%+v-%+v", n.Op(), n.FuncName().Sym())
-		dumpNodeHeader(w, n)
-		return
-
 	case OASOP:
 		n := n.(*AssignOpStmt)
 		fmt.Fprintf(w, "%+v-%+v", n.Op(), n.AsOp)
diff --git a/src/cmd/compile/internal/ir/node_gen.go b/src/cmd/compile/internal/ir/node_gen.go
index 27a5311748..a1ce9a4e9d 100644
--- a/src/cmd/compile/internal/ir/node_gen.go
+++ b/src/cmd/compile/internal/ir/node_gen.go
@@ -209,23 +209,6 @@ func (n *CallExpr) editChildren(edit func(Node) Node) {
 	editList(n.Body, edit)
 }
 
-func (n *CallPartExpr) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
-func (n *CallPartExpr) copy() Node {
-	c := *n
-	c.init = c.init.Copy()
-	return &c
-}
-func (n *CallPartExpr) doChildren(do func(Node) error) error {
-	var err error
-	err = maybeDoList(n.init, err, do)
-	err = maybeDo(n.X, err, do)
-	return err
-}
-func (n *CallPartExpr) editChildren(edit func(Node) Node) {
-	editList(n.init, edit)
-	n.X = maybeEdit(n.X, edit)
-}
-
 func (n *CaseClause) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
 func (n *CaseClause) copy() Node {
 	c := *n
@@ -655,21 +638,6 @@ func (n *MapType) editChildren(edit func(Node) Node) {
 	n.Elem = maybeEdit(n.Elem, edit)
 }
 
-func (n *MethodExpr) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
-func (n *MethodExpr) copy() Node {
-	c := *n
-	c.init = c.init.Copy()
-	return &c
-}
-func (n *MethodExpr) doChildren(do func(Node) error) error {
-	var err error
-	err = maybeDoList(n.init, err, do)
-	return err
-}
-func (n *MethodExpr) editChildren(edit func(Node) Node) {
-	editList(n.init, edit)
-}
-
 func (n *Name) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
 func (n *Name) copy() Node                    { panic("Name.copy") }
 func (n *Name) doChildren(do func(Node) error) error {
diff --git a/src/cmd/compile/internal/staticinit/sched.go b/src/cmd/compile/internal/staticinit/sched.go
index 2711f6cec0..d8f51766de 100644
--- a/src/cmd/compile/internal/staticinit/sched.go
+++ b/src/cmd/compile/internal/staticinit/sched.go
@@ -104,7 +104,7 @@ func (s *Schedule) staticcopy(l *ir.Name, loff int64, rn *ir.Name, typ *types.Ty
 
 	switch r.Op() {
 	case ir.OMETHEXPR:
-		r = r.(*ir.MethodExpr).FuncName()
+		r = r.(*ir.SelectorExpr).FuncName()
 		fallthrough
 	case ir.ONAME:
 		r := r.(*ir.Name)
@@ -165,7 +165,7 @@ func (s *Schedule) staticcopy(l *ir.Name, loff int64, rn *ir.Name, typ *types.Ty
 			}
 			x := e.Expr
 			if x.Op() == ir.OMETHEXPR {
-				x = x.(*ir.MethodExpr).FuncName()
+				x = x.(*ir.SelectorExpr).FuncName()
 			}
 			if x.Op() == ir.ONAME && s.staticcopy(l, loff+e.Xoffset, x.(*ir.Name), typ) {
 				continue
@@ -195,7 +195,7 @@ func (s *Schedule) StaticAssign(l *ir.Name, loff int64, r ir.Node, typ *types.Ty
 		return s.staticcopy(l, loff, r, typ)
 
 	case ir.OMETHEXPR:
-		r := r.(*ir.MethodExpr)
+		r := r.(*ir.SelectorExpr)
 		return s.staticcopy(l, loff, r.FuncName(), typ)
 
 	case ir.ONIL:
@@ -461,7 +461,7 @@ func StaticLoc(n ir.Node) (name *ir.Name, offset int64, ok bool) {
 		return n, 0, true
 
 	case ir.OMETHEXPR:
-		n := n.(*ir.MethodExpr)
+		n := n.(*ir.SelectorExpr)
 		return StaticLoc(n.FuncName())
 
 	case ir.ODOT:
diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 3e7a880c2a..0682548c27 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -626,10 +626,8 @@ func tcDot(n *ir.SelectorExpr, top int) ir.Node {
 	}
 
 	if (n.Op() == ir.ODOTINTER || n.Op() == ir.ODOTMETH) && top&ctxCallee == 0 {
-		// Create top-level function.
-		fn := makepartialcall(n)
-
-		return ir.NewCallPartExpr(n.Pos(), n.X, n.Selection, fn)
+		n.SetOp(ir.OCALLPART)
+		n.SetType(MethodValueWrapper(n).Type())
 	}
 	return n
 }
diff --git a/src/cmd/compile/internal/typecheck/func.go b/src/cmd/compile/internal/typecheck/func.go
index ed4f3ad4fe..c58fef10ec 100644
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@@ -91,7 +91,7 @@ func ClosureType(clo *ir.ClosureExpr) *types.Type {
 // PartialCallType returns the struct type used to hold all the information
 // needed in the closure for n (n must be a OCALLPART node).
 // The address of a variable of the returned type can be cast to a func.
-func PartialCallType(n *ir.CallPartExpr) *types.Type {
+func PartialCallType(n *ir.SelectorExpr) *types.Type {
 	t := types.NewStruct(types.NoPkg, []*types.Field{
 		types.NewField(base.Pos, Lookup("F"), types.Types[types.TUINTPTR]),
 		types.NewField(base.Pos, Lookup("R"), n.X.Type()),
@@ -247,9 +247,17 @@ func closurename(outerfunc *ir.Func) *types.Sym {
 // globClosgen is like Func.Closgen, but for the global scope.
 var globClosgen int32
 
-// makepartialcall returns a DCLFUNC node representing the wrapper function (*-fm) needed
-// for partial calls.
-func makepartialcall(dot *ir.SelectorExpr) *ir.Func {
+// MethodValueWrapper returns the DCLFUNC node representing the
+// wrapper function (*-fm) needed for the given method value. If the
+// wrapper function hasn't already been created yet, it's created and
+// added to Target.Decls.
+//
+// TODO(mdempsky): Move into walk. This isn't part of type checking.
+func MethodValueWrapper(dot *ir.SelectorExpr) *ir.Func {
+	if dot.Op() != ir.OCALLPART {
+		base.Fatalf("MethodValueWrapper: unexpected %v (%v)", dot, dot.Op())
+	}
+
 	t0 := dot.Type()
 	meth := dot.Sel
 	rcvrtype := dot.X.Type()
diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 3b071a61ab..e35cbcafa2 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -1252,17 +1252,6 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.pos(n.Pos())
 		w.value(n.Type(), n.Val())
 
-	case ir.OMETHEXPR:
-		// Special case: explicit name of func (*T) method(...) is turned into pkg.(*T).method,
-		// but for export, this should be rendered as (*pkg.T).meth.
-		// These nodes have the special property that they are names with a left OTYPE and a right ONAME.
-		n := n.(*ir.MethodExpr)
-		w.op(ir.OXDOT)
-		w.pos(n.Pos())
-		w.op(ir.OTYPE)
-		w.typ(n.T) // n.Left.Op == OTYPE
-		w.selector(n.Method.Sym)
-
 	case ir.ONAME:
 		// Package scope name.
 		n := n.(*ir.Name)
@@ -1336,15 +1325,7 @@ func (w *exportWriter) expr(n ir.Node) {
 	// case OSTRUCTKEY:
 	//	unreachable - handled in case OSTRUCTLIT by elemList
 
-	case ir.OCALLPART:
-		// An OCALLPART is an OXDOT before type checking.
-		n := n.(*ir.CallPartExpr)
-		w.op(ir.OXDOT)
-		w.pos(n.Pos())
-		w.expr(n.X)
-		w.selector(n.Method.Sym)
-
-	case ir.OXDOT, ir.ODOT, ir.ODOTPTR, ir.ODOTINTER, ir.ODOTMETH:
+	case ir.OXDOT, ir.ODOT, ir.ODOTPTR, ir.ODOTINTER, ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
 		n := n.(*ir.SelectorExpr)
 		w.op(ir.OXDOT)
 		w.pos(n.Pos())
diff --git a/src/cmd/compile/internal/typecheck/typecheck.go b/src/cmd/compile/internal/typecheck/typecheck.go
index e23c249ff2..ff9178b597 100644
--- a/src/cmd/compile/internal/typecheck/typecheck.go
+++ b/src/cmd/compile/internal/typecheck/typecheck.go
@@ -1176,19 +1176,16 @@ func typecheckMethodExpr(n *ir.SelectorExpr) (res ir.Node) {
 		return n
 	}
 
-	me := ir.NewMethodExpr(n.Pos(), n.X.Type(), m)
-	me.SetType(NewMethodType(m.Type, n.X.Type()))
-	f := NewName(ir.MethodSym(t, m.Sym))
-	f.Class_ = ir.PFUNC
-	f.SetType(me.Type())
-	me.FuncName_ = f
+	n.SetOp(ir.OMETHEXPR)
+	n.Selection = m
+	n.SetType(NewMethodType(m.Type, n.X.Type()))
 
 	// Issue 25065. Make sure that we emit the symbol for a local method.
 	if base.Ctxt.Flag_dynlink && !inimport && (t.Sym() == nil || t.Sym().Pkg == types.LocalPkg) {
-		NeedFuncSym(me.FuncName_.Sym())
+		NeedFuncSym(n.FuncName().Sym())
 	}
 
-	return me
+	return n
 }
 
 func derefall(t *types.Type) *types.Type {
@@ -1422,7 +1419,7 @@ notenough:
 			// Method expressions have the form T.M, and the compiler has
 			// rewritten those to ONAME nodes but left T in Left.
 			if call.Op() == ir.OMETHEXPR {
-				call := call.(*ir.MethodExpr)
+				call := call.(*ir.SelectorExpr)
 				base.Errorf("not enough arguments in call to method expression %v%s", call, details)
 			} else {
 				base.Errorf("not enough arguments in call to %v%s", call, details)
diff --git a/src/cmd/compile/internal/walk/closure.go b/src/cmd/compile/internal/walk/closure.go
index 30f86f0965..9bcb82bc03 100644
--- a/src/cmd/compile/internal/walk/closure.go
+++ b/src/cmd/compile/internal/walk/closure.go
@@ -151,7 +151,7 @@ func walkClosure(clo *ir.ClosureExpr, init *ir.Nodes) ir.Node {
 	return walkExpr(cfn, init)
 }
 
-func walkCallPart(n *ir.CallPartExpr, init *ir.Nodes) ir.Node {
+func walkCallPart(n *ir.SelectorExpr, init *ir.Nodes) ir.Node {
 	// Create closure in the form of a composite literal.
 	// For x.M with receiver (x) type T, the generated code looks like:
 	//
@@ -176,7 +176,7 @@ func walkCallPart(n *ir.CallPartExpr, init *ir.Nodes) ir.Node {
 
 	clos := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, ir.TypeNode(typ).(ir.Ntype), nil)
 	clos.SetEsc(n.Esc())
-	clos.List = []ir.Node{ir.NewUnaryExpr(base.Pos, ir.OCFUNC, n.Func.Nname), n.X}
+	clos.List = []ir.Node{ir.NewUnaryExpr(base.Pos, ir.OCFUNC, typecheck.MethodValueWrapper(n).Nname), n.X}
 
 	addr := typecheck.NodAddr(clos)
 	addr.SetEsc(n.Esc())
diff --git a/src/cmd/compile/internal/walk/complit.go b/src/cmd/compile/internal/walk/complit.go
index 8c4f9583ef..fadcd87f25 100644
--- a/src/cmd/compile/internal/walk/complit.go
+++ b/src/cmd/compile/internal/walk/complit.go
@@ -539,7 +539,7 @@ func anylit(n ir.Node, var_ ir.Node, init *ir.Nodes) {
 		appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, n))
 
 	case ir.OMETHEXPR:
-		n := n.(*ir.MethodExpr)
+		n := n.(*ir.SelectorExpr)
 		anylit(n.FuncName(), var_, init)
 
 	case ir.OPTRLIT:
@@ -666,7 +666,7 @@ func genAsStatic(as *ir.AssignStmt) {
 		staticdata.InitConst(name, offset, r, int(r.Type().Width))
 		return
 	case ir.OMETHEXPR:
-		r := r.(*ir.MethodExpr)
+		r := r.(*ir.SelectorExpr)
 		staticdata.InitFunc(name, offset, r.FuncName())
 		return
 	case ir.ONAME:
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
index fd0dd5b062..7cc6758024 100644
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -100,7 +100,7 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 
 	case ir.OMETHEXPR:
 		// TODO(mdempsky): Do this right after type checking.
-		n := n.(*ir.MethodExpr)
+		n := n.(*ir.SelectorExpr)
 		return n.FuncName()
 
 	case ir.ONOT, ir.ONEG, ir.OPLUS, ir.OBITNOT, ir.OREAL, ir.OIMAG, ir.OSPTR, ir.OITAB, ir.OIDATA:
@@ -306,7 +306,7 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 		return walkClosure(n.(*ir.ClosureExpr), init)
 
 	case ir.OCALLPART:
-		return walkCallPart(n.(*ir.CallPartExpr), init)
+		return walkCallPart(n.(*ir.SelectorExpr), init)
 	}
 
 	// No return! Each case must return (or panic),
diff --git a/src/cmd/compile/internal/walk/order.go b/src/cmd/compile/internal/walk/order.go
index ebbd467570..0dd76ccee9 100644
--- a/src/cmd/compile/internal/walk/order.go
+++ b/src/cmd/compile/internal/walk/order.go
@@ -1310,7 +1310,7 @@ func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
 		return n
 
 	case ir.OCALLPART:
-		n := n.(*ir.CallPartExpr)
+		n := n.(*ir.SelectorExpr)
 		n.X = o.expr(n.X, nil)
 		if n.Transient() {
 			t := typecheck.PartialCallType(n)