cmd/compile/internal/ir: remove OrigNode

The OrigNode functionality used to be relevant to the typecheck
frontend, because we wanted to report errors using the same syntax as
the user originally wrote. However, now that types2 handles all
spec-required error diagnostics, there's no need to preserve original
nodes anymore.

Change-Id: I64a0540b8952513913021e7b84d165beb1f9f801
Reviewed-on: https://go-review.googlesource.com/c/go/+/526397
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/compile/internal/ir/copy.go

@@ -5,71 +5,26 @@
 package ir
 
 import (
-	"cmd/compile/internal/base"
 	"cmd/internal/src"
 )
 
-// A Node may implement the Orig and SetOrig method to
-// maintain a pointer to the "unrewritten" form of a Node.
-// If a Node does not implement OrigNode, it is its own Orig.
+// Orig returns n.
 //
-// Note that both SepCopy and Copy have definitions compatible
-// with a Node that does not implement OrigNode: such a Node
-// is its own Orig, and in that case, that's what both want to return
-// anyway (SepCopy unconditionally, and Copy only when the input
-// is its own Orig as well, but if the output does not implement
-// OrigNode, then neither does the input, making the condition true).
-type OrigNode interface {
-	Node
-	Orig() Node
-	SetOrig(Node)
-}
-
-// origNode may be embedded into a Node to make it implement OrigNode.
-type origNode struct {
-	orig Node `mknode:"-"`
-}
-
-func (n *origNode) Orig() Node     { return n.orig }
-func (n *origNode) SetOrig(o Node) { n.orig = o }
-
-// Orig returns the “original” node for n.
-// If n implements OrigNode, Orig returns n.Orig().
-// Otherwise Orig returns n itself.
+// TODO(mdempsky): Remove.
 func Orig(n Node) Node {
-	if n, ok := n.(OrigNode); ok {
-		o := n.Orig()
-		if o == nil {
-			Dump("Orig nil", n)
-			base.Fatalf("Orig returned nil")
-		}
-		return o
-	}
 	return n
 }
 
-// SepCopy returns a separate shallow copy of n,
-// breaking any Orig link to any other nodes.
+// SepCopy returns a shallow copy of n.
+//
+// TODO(mdempsky): Replace with Copy.
 func SepCopy(n Node) Node {
-	n = n.copy()
-	if n, ok := n.(OrigNode); ok {
-		n.SetOrig(n)
-	}
-	return n
+	return n.copy()
 }
 
 // Copy returns a shallow copy of n.
-// If Orig(n) == n, then Orig(Copy(n)) == the copy.
-// Otherwise the Orig link is preserved as well.
-//
-// The specific semantics surrounding Orig are subtle but right for most uses.
-// See issues #26855 and #27765 for pitfalls.
 func Copy(n Node) Node {
-	c := n.copy()
-	if n, ok := n.(OrigNode); ok && n.Orig() == n {
-		c.(OrigNode).SetOrig(c)
-	}
-	return c
+	return n.copy()
 }
 
 // DeepCopy returns a “deep” copy of n, with its entire structure copied

src/cmd/compile/internal/ir/expr.go

@@ -188,7 +188,6 @@ func (n *BinaryExpr) SetOp(op Op) {
 // A CallExpr is a function call X(Args).
 type CallExpr struct {
 	miniExpr
-	origNode
 	X         Node
 	Args      Nodes
 	RType     Node    `mknode:"-"` // see reflectdata/helpers.go
@@ -200,7 +199,6 @@ type CallExpr struct {
 func NewCallExpr(pos src.XPos, op Op, fun Node, args []Node) *CallExpr {
 	n := &CallExpr{X: fun}
 	n.pos = pos
-	n.orig = n
 	n.SetOp(op)
 	n.Args = args
 	return n
@@ -234,7 +232,6 @@ type ClosureExpr struct {
 // Before type-checking, the type is Ntype.
 type CompLitExpr struct {
 	miniExpr
-	origNode
 	List     Nodes // initialized values
 	RType    Node  `mknode:"-"` // *runtime._type for OMAPLIT map types
 	Prealloc *Name
@@ -251,7 +248,6 @@ func NewCompLitExpr(pos src.XPos, op Op, typ *types.Type, list []Node) *CompLitE
 	if typ != nil {
 		n.SetType(typ)
 	}
-	n.orig = n
 	return n
 }
 

src/cmd/compile/internal/ir/stmt.go

@@ -373,15 +373,13 @@ func NewRangeStmt(pos src.XPos, key, value, x Node, body []Node, distinctVars bo
 // A ReturnStmt is a return statement.
 type ReturnStmt struct {
 	miniStmt
-	origNode       // for typecheckargs rewrite
-	Results  Nodes // return list
+	Results Nodes // return list
 }
 
 func NewReturnStmt(pos src.XPos, results []Node) *ReturnStmt {
 	n := &ReturnStmt{}
 	n.pos = pos
 	n.op = ORETURN
-	n.orig = n
 	n.Results = results
 	return n
 }

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

@@ -169,9 +169,6 @@ func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
 		base.Pos = lno
 	}()
 
-	// Save original node (including n.Right)
-	n.SetOrig(ir.Copy(n))
-
 	ir.SetPos(n)
 
 	t := n.Type()

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

@@ -624,11 +624,6 @@ func typecheckargs(n ir.InitNode) {
 		return
 	}
 
-	// Save n as n.Orig for fmt.go.
-	if ir.Orig(n) == n {
-		n.(ir.OrigNode).SetOrig(ir.SepCopy(n))
-	}
-
 	// Rewrite f(g()) into t1, t2, ... = g(); f(t1, t2, ...).
 	RewriteMultiValueCall(n, list[0])
 }