[dev.typeparams] cmd/compile: better Call constructor

Historically, it's been tedious to create and typecheck ir.OCALL
nodes, except by handing them off entirely to typecheck. This is
because typecheck needed context on whether the call is an expression
or statement, and to set flags like Func.ClosureCalled and
CallExpr.Use.

However, those flags have now been removed entirely by recent CLs, so
we can instead just provide a better typecheck.Call function for
constructing and typechecking arbitrary call nodes. Notably, this
simplifies things for unified IR, which can now incrementally
typecheck call expressions as it goes without worrying about context.

Change-Id: Icbdc55c3bd8be84a242323bc45006f9dec09fdcd
Reviewed-on: https://go-review.googlesource.com/c/go/+/332692
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

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

@@ -1526,9 +1526,7 @@ func (r *reader) expr() ir.Node {
 		pos := r.pos()
 		args := r.exprs()
 		dots := r.bool()
-		n := ir.NewCallExpr(pos, ir.OCALL, fun, args)
-		n.IsDDD = dots
-		return n
+		return typecheck.Call(pos, fun, args, dots)
 
 	case exprTypeSwitchGuard:
 		pos := r.pos()
@@ -2281,8 +2279,8 @@ func addTailCall(pos src.XPos, fn *ir.Func, recv ir.Node, method *types.Field) {
 
 	fn.SetWrapper(true) // TODO(mdempsky): Leave unset for tail calls?
 
-	call := ir.NewCallExpr(pos, ir.OCALL, ir.NewSelectorExpr(pos, ir.OXDOT, recv, method.Sym), args)
-	call.IsDDD = method.Type.IsVariadic()
+	dot := ir.NewSelectorExpr(pos, ir.OXDOT, recv, method.Sym)
+	call := typecheck.Call(pos, dot, args, method.Type.IsVariadic()).(*ir.CallExpr)
 
 	if method.Type.NumResults() == 0 {
 		fn.Body.Append(call)

src/cmd/compile/internal/reflectdata/alg.go

@@ -679,8 +679,7 @@ func EqString(s, t ir.Node) (eqlen *ir.BinaryExpr, eqmem *ir.CallExpr) {
 
 	fn := typecheck.LookupRuntime("memequal")
 	fn = typecheck.SubstArgTypes(fn, types.Types[types.TUINT8], types.Types[types.TUINT8])
-	call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, []ir.Node{sptr, tptr, ir.Copy(slen)})
-	typecheck.Call(call)
+	call := typecheck.Call(base.Pos, fn, []ir.Node{sptr, tptr, ir.Copy(slen)}, false).(*ir.CallExpr)
 
 	cmp := ir.NewBinaryExpr(base.Pos, ir.OEQ, slen, tlen)
 	cmp = typecheck.Expr(cmp).(*ir.BinaryExpr)
@@ -716,8 +715,7 @@ func EqInterface(s, t ir.Node) (eqtab *ir.BinaryExpr, eqdata *ir.CallExpr) {
 	sdata.SetTypecheck(1)
 	tdata.SetTypecheck(1)
 
-	call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, []ir.Node{stab, sdata, tdata})
-	typecheck.Call(call)
+	call := typecheck.Call(base.Pos, fn, []ir.Node{stab, sdata, tdata}, false).(*ir.CallExpr)
 
 	cmp := ir.NewBinaryExpr(base.Pos, ir.OEQ, stab, ttab)
 	cmp = typecheck.Expr(cmp).(*ir.BinaryExpr)

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

@@ -13,6 +13,7 @@ import (
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
+	"cmd/internal/src"
 )
 
 // Function collecting autotmps generated during typechecking,
@@ -34,18 +35,10 @@ func Stmt(n ir.Node) ir.Node       { return typecheck(n, ctxStmt) }
 func Exprs(exprs []ir.Node) { typecheckslice(exprs, ctxExpr) }
 func Stmts(stmts []ir.Node) { typecheckslice(stmts, ctxStmt) }
 
-func Call(call *ir.CallExpr) {
-	t := call.X.Type()
-	if t == nil {
-		panic("misuse of Call")
-	}
-	ctx := ctxStmt
-	if t.NumResults() > 0 {
-		ctx = ctxExpr | ctxMultiOK
-	}
-	if typecheck(call, ctx) != call {
-		panic("bad typecheck")
-	}
+func Call(pos src.XPos, callee ir.Node, args []ir.Node, dots bool) ir.Node {
+	call := ir.NewCallExpr(pos, ir.OCALL, callee, args)
+	call.IsDDD = dots
+	return typecheck(call, ctxStmt|ctxExpr)
 }
 
 func Callee(n ir.Node) ir.Node {

src/cmd/compile/internal/walk/walk.go

@@ -113,8 +113,7 @@ func vmkcall(fn ir.Node, t *types.Type, init *ir.Nodes, va []ir.Node) *ir.CallEx
 		base.Fatalf("vmkcall %v needs %v args got %v", fn, n, len(va))
 	}
 
-	call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, va)
-	typecheck.Call(call)
+	call := typecheck.Call(base.Pos, fn, va, false).(*ir.CallExpr)
 	call.SetType(t)
 	return walkExpr(call, init).(*ir.CallExpr)
 }