cmd/compile: construct more IR nodes as typed

As of this CL, all OLITERAL, OLINKSYMOFFSET, ONIL, and OTYPE nodes are
constructed as typed and typechecked.

Change-Id: I39b2ad772a9b0419c701890a505a0949f9ea456e
Reviewed-on: https://go-review.googlesource.com/c/go/+/520795
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

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

@@ -106,9 +106,8 @@ func NewBasicLit(pos src.XPos, val constant.Value) Node {
 	n := &BasicLit{val: val}
 	n.op = OLITERAL
 	n.pos = pos
-	if k := val.Kind(); k != constant.Unknown {
-		n.SetType(idealType(k))
-	}
+	n.SetType(idealType(val.Kind()))
+	n.SetTypecheck(1)
 	return n
 }
 
@@ -432,15 +431,19 @@ func (n *MakeExpr) SetOp(op Op) {
 }
 
 // A NilExpr represents the predefined untyped constant nil.
-// (It may be copied and assigned a type, though.)
 type NilExpr struct {
 	miniExpr
 }
 
-func NewNilExpr(pos src.XPos) *NilExpr {
+func NewNilExpr(pos src.XPos, typ *types.Type) *NilExpr {
+	if typ == nil {
+		base.FatalfAt(pos, "missing type")
+	}
 	n := &NilExpr{}
 	n.pos = pos
 	n.op = ONIL
+	n.SetType(typ)
+	n.SetTypecheck(1)
 	return n
 }
 
@@ -498,9 +501,13 @@ type LinksymOffsetExpr struct {
 }
 
 func NewLinksymOffsetExpr(pos src.XPos, lsym *obj.LSym, offset int64, typ *types.Type) *LinksymOffsetExpr {
+	if typ == nil {
+		base.FatalfAt(pos, "nil type")
+	}
 	n := &LinksymOffsetExpr{Linksym: lsym, Offset_: offset}
 	n.typ = typ
 	n.op = OLINKSYMOFFSET
+	n.SetTypecheck(1)
 	return n
 }
 

src/cmd/compile/internal/noder/helpers.go

@@ -66,7 +66,7 @@ func FixValue(typ *types.Type, val constant.Value) constant.Value {
 }
 
 func Nil(pos src.XPos, typ *types.Type) ir.Node {
-	return typed(typ, ir.NewNilExpr(pos))
+	return ir.NewNilExpr(pos, typ)
 }
 
 // Expressions

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

@@ -17,18 +17,15 @@ import (
 
 // MakeDotArgs package all the arguments that match a ... T parameter into a []T.
 func MakeDotArgs(pos src.XPos, typ *types.Type, args []ir.Node) ir.Node {
-	var n ir.Node
 	if len(args) == 0 {
-		n = ir.NewNilExpr(pos)
-		n.SetType(typ)
-	} else {
+		return ir.NewNilExpr(pos, typ)
+	}
+
 	args = append([]ir.Node(nil), args...)
 	lit := ir.NewCompLitExpr(pos, ir.OCOMPLIT, typ, args)
 	lit.SetImplicit(true)
-		n = lit
-	}
 
-	n = Expr(n)
+	n := Expr(lit)
 	if n.Type() == nil {
 		base.FatalfAt(pos, "mkdotargslice: typecheck failed")
 	}

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

@@ -120,9 +120,7 @@ func LinksymAddr(pos src.XPos, lsym *obj.LSym, typ *types.Type) *ir.AddrExpr {
 }
 
 func NodNil() ir.Node {
-	n := ir.NewNilExpr(base.Pos)
-	n.SetType(types.Types[types.TNIL])
-	return n
+	return ir.NewNilExpr(base.Pos, types.Types[types.TNIL])
 }
 
 // AddImplicitDots finds missing fields in obj.field that

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

@@ -177,7 +177,7 @@ func typecheck(n ir.Node, top int) (res ir.Node) {
 	// But re-typecheck ONAME/OTYPE/OLITERAL/OPACK node in case context has changed.
 	if n.Typecheck() == 1 || n.Typecheck() == 3 {
 		switch n.Op() {
-		case ir.ONAME, ir.OTYPE, ir.OLITERAL:
+		case ir.ONAME:
 			break
 
 		default:
@@ -230,22 +230,6 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		base.Fatalf("typecheck %v", n.Op())
 		panic("unreachable")
 
-	case ir.OLITERAL:
-		if n.Sym() == nil && n.Type() == nil {
-			base.Fatalf("literal missing type: %v", n)
-		}
-		return n
-
-	case ir.ONIL:
-		return n
-
-	// names
-	case ir.ONONAME:
-		// Note: adderrorname looks for this string and
-		// adds context about the outer expression
-		base.FatalfAt(n.Pos(), "undefined: %v", n.Sym())
-		panic("unreachable")
-
 	case ir.ONAME:
 		n := n.(*ir.Name)
 		if n.BuiltinOp != 0 {
@@ -267,14 +251,6 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		}
 		return n
 
-	case ir.OLINKSYMOFFSET:
-		// type already set
-		return n
-
-	// types (ODEREF is with exprs)
-	case ir.OTYPE:
-		return n
-
 	// type or expr
 	case ir.ODEREF:
 		n := n.(*ir.StarExpr)

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

@@ -70,6 +70,7 @@ func InitUniverse() {
 	types.InitTypes(func(sym *types.Sym, typ *types.Type) types.Object {
 		n := ir.NewDeclNameAt(src.NoXPos, ir.OTYPE, sym)
 		n.SetType(typ)
+		n.SetTypecheck(1)
 		sym.Def = n
 		return n
 	})