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

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package typecheck

import (
	"cmd/compile/internal/base"
	"cmd/compile/internal/ir"
	"cmd/compile/internal/types"

	"fmt"
	"go/constant"
	"go/token"
)

// package all the arguments that match a ... T parameter into a []T.
func MakeDotArgs(typ *types.Type, args []ir.Node) ir.Node {
	var n ir.Node
	if len(args) == 0 {
		n = NodNil()
		n.SetType(typ)
	} else {
		lit := ir.NewCompLitExpr(base.Pos, ir.OCOMPLIT, ir.TypeNode(typ), nil)
		lit.List.Append(args...)
		lit.SetImplicit(true)
		n = lit
	}

	n = Expr(n)
	if n.Type() == nil {
		base.Fatalf("mkdotargslice: typecheck failed")
	}
	return n
}

// FixVariadicCall rewrites calls to variadic functions to use an
// explicit ... argument if one is not already present.
func FixVariadicCall(call *ir.CallExpr) {
	fntype := call.X.Type()
	if !fntype.IsVariadic() || call.IsDDD {
		return
	}

	vi := fntype.NumParams() - 1
	vt := fntype.Params().Field(vi).Type

	args := call.Args
	extra := args[vi:]
	slice := MakeDotArgs(vt, extra)
	for i := range extra {
		extra[i] = nil // allow GC
	}

	call.Args = append(args[:vi], slice)
	call.IsDDD = true
}

// ClosureType returns the struct type used to hold all the information
// needed in the closure for clo (clo must be a OCLOSURE node).
// The address of a variable of the returned type can be cast to a func.
func ClosureType(clo *ir.ClosureExpr) *types.Type {
	// Create closure in the form of a composite literal.
	// supposing the closure captures an int i and a string s
	// and has one float64 argument and no results,
	// the generated code looks like:
	//
	//	clos = &struct{.F uintptr; i *int; s *string}{func.1, &i, &s}
	//
	// The use of the struct provides type information to the garbage
	// collector so that it can walk the closure. We could use (in this case)
	// [3]unsafe.Pointer instead, but that would leave the gc in the dark.
	// The information appears in the binary in the form of type descriptors;
	// the struct is unnamed so that closures in multiple packages with the
	// same struct type can share the descriptor.
	fields := []*types.Field{
		types.NewField(base.Pos, Lookup(".F"), types.Types[types.TUINTPTR]),
	}
	for _, v := range clo.Func.ClosureVars {
		typ := v.Type()
		if !v.Byval() {
			typ = types.NewPtr(typ)
		}
		fields = append(fields, types.NewField(base.Pos, v.Sym(), typ))
	}
	typ := types.NewStruct(types.NoPkg, fields)
	typ.SetNoalg(true)
	return typ
}

// 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.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()),
	})
	t.SetNoalg(true)
	return t
}

// True if we are typechecking an inline body in ImportedBody below. We use this
// flag to not create a new closure function in tcClosure when we are just
// typechecking an inline body, as opposed to the body of a real function.
var inTypeCheckInl bool

// ImportedBody returns immediately if the inlining information for fn is
// populated. Otherwise, fn must be an imported function. If so, ImportedBody
// loads in the dcls and body for fn, and typechecks as needed.
func ImportedBody(fn *ir.Func) {
	if fn.Inl.Body != nil {
		return
	}
	lno := ir.SetPos(fn.Nname)

	// When we load an inlined body, we need to allow OADDR
	// operations on untyped expressions. We will fix the
	// addrtaken flags on all the arguments of the OADDR with the
	// computeAddrtaken call below (after we typecheck the body).
	// TODO: export/import types and addrtaken marks along with inlined bodies,
	// so this will be unnecessary.
	IncrementalAddrtaken = false
	defer func() {
		if DirtyAddrtaken {
			ComputeAddrtaken(fn.Inl.Body) // compute addrtaken marks once types are available
			DirtyAddrtaken = false
		}
		IncrementalAddrtaken = true
	}()

	ImportBody(fn)

	// Stmts(fn.Inl.Body) below is only for imported functions;
	// their bodies may refer to unsafe as long as the package
	// was marked safe during import (which was checked then).
	// the ->inl of a local function has been typechecked before CanInline copied it.
	pkg := fnpkg(fn.Nname)

	if pkg == types.LocalPkg || pkg == nil {
		return // ImportedBody on local function
	}

	if base.Flag.LowerM > 2 || base.Debug.Export != 0 {
		fmt.Printf("typecheck import [%v] %L { %v }\n", fn.Sym(), fn, ir.Nodes(fn.Inl.Body))
	}

	if !go117ExportTypes {
		// If we didn't export & import types, typecheck the code here.
		savefn := ir.CurFunc
		ir.CurFunc = fn
		if inTypeCheckInl {
			base.Fatalf("inTypeCheckInl should not be set recursively")
		}
		inTypeCheckInl = true
		Stmts(fn.Inl.Body)
		inTypeCheckInl = false
		ir.CurFunc = savefn
	}

	base.Pos = lno
}

// Get the function's package. For ordinary functions it's on the ->sym, but for imported methods
// the ->sym can be re-used in the local package, so peel it off the receiver's type.
func fnpkg(fn *ir.Name) *types.Pkg {
	if ir.IsMethod(fn) {
		// method
		rcvr := fn.Type().Recv().Type

		if rcvr.IsPtr() {
			rcvr = rcvr.Elem()
		}
		if rcvr.Sym() == nil {
			base.Fatalf("receiver with no sym: [%v] %L  (%v)", fn.Sym(), fn, rcvr)
		}
		return rcvr.Sym().Pkg
	}

	// non-method
	return fn.Sym().Pkg
}

// ClosureName generates a new unique name for a closure within
// outerfunc.
func ClosureName(outerfunc *ir.Func) *types.Sym {
	outer := "glob."
	prefix := "func"
	gen := &globClosgen

	if outerfunc != nil {
		if outerfunc.OClosure != nil {
			prefix = ""
		}

		outer = ir.FuncName(outerfunc)

		// There may be multiple functions named "_". In those
		// cases, we can't use their individual Closgens as it
		// would lead to name clashes.
		if !ir.IsBlank(outerfunc.Nname) {
			gen = &outerfunc.Closgen
		}
	}

	*gen++
	return Lookup(fmt.Sprintf("%s.%s%d", outer, prefix, *gen))
}

// globClosgen is like Func.Closgen, but for the global scope.
var globClosgen int32

// 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()
	sym := ir.MethodSymSuffix(rcvrtype, meth, "-fm")

	if sym.Uniq() {
		return sym.Def.(*ir.Func)
	}
	sym.SetUniq(true)

	savecurfn := ir.CurFunc
	saveLineNo := base.Pos
	ir.CurFunc = nil

	// Set line number equal to the line number where the method is declared.
	if pos := dot.Selection.Pos; pos.IsKnown() {
		base.Pos = pos
	}
	// Note: !dot.Selection.Pos.IsKnown() happens for method expressions where
	// the method is implicitly declared. The Error method of the
	// built-in error type is one such method.  We leave the line
	// number at the use of the method expression in this
	// case. See issue 29389.

	tfn := ir.NewFuncType(base.Pos, nil,
		NewFuncParams(t0.Params(), true),
		NewFuncParams(t0.Results(), false))

	fn := DeclFunc(sym, tfn)
	fn.SetDupok(true)
	fn.SetNeedctxt(true)
	fn.SetWrapper(true)

	// Declare and initialize variable holding receiver.
	ptr := ir.NewNameAt(base.Pos, Lookup(".this"))
	ptr.Class = ir.PAUTOHEAP
	ptr.SetType(rcvrtype)
	ptr.Curfn = fn
	ptr.SetIsClosureVar(true)
	ptr.SetByval(true)
	fn.ClosureVars = append(fn.ClosureVars, ptr)

	call := ir.NewCallExpr(base.Pos, ir.OCALL, ir.NewSelectorExpr(base.Pos, ir.OXDOT, ptr, meth), nil)
	call.Args = ir.ParamNames(tfn.Type())
	call.IsDDD = tfn.Type().IsVariadic()

	var body ir.Node = call
	if t0.NumResults() != 0 {
		ret := ir.NewReturnStmt(base.Pos, nil)
		ret.Results = []ir.Node{call}
		body = ret
	}

	fn.Body = []ir.Node{body}
	FinishFuncBody()

	Func(fn)
	// Need to typecheck the body of the just-generated wrapper.
	// typecheckslice() requires that Curfn is set when processing an ORETURN.
	ir.CurFunc = fn
	Stmts(fn.Body)
	sym.Def = fn
	Target.Decls = append(Target.Decls, fn)
	ir.CurFunc = savecurfn
	base.Pos = saveLineNo

	return fn
}

// tcClosure typechecks an OCLOSURE node. It also creates the named
// function associated with the closure.
// TODO: This creation of the named function should probably really be done in a
// separate pass from type-checking.
func tcClosure(clo *ir.ClosureExpr, top int) {
	fn := clo.Func
	// Set current associated iota value, so iota can be used inside
	// function in ConstSpec, see issue #22344
	if x := getIotaValue(); x >= 0 {
		fn.Iota = x
	}

	fn.SetClosureCalled(top&ctxCallee != 0)

	// Do not typecheck fn twice, otherwise, we will end up pushing
	// fn to Target.Decls multiple times, causing InitLSym called twice.
	// See #30709
	if fn.Typecheck() == 1 {
		clo.SetType(fn.Type())
		return
	}

	// Don't give a name and add to Target.Decls if we are typechecking an inlined
	// body in ImportedBody(), since we only want to create the named function
	// when the closure is actually inlined (and then we force a typecheck
	// explicitly in (*inlsubst).node()).
	if !inTypeCheckInl {
		fn.Nname.SetSym(ClosureName(ir.CurFunc))
		ir.MarkFunc(fn.Nname)
	}
	Func(fn)
	clo.SetType(fn.Type())

	// Type check the body now, but only if we're inside a function.
	// At top level (in a variable initialization: curfn==nil) we're not
	// ready to type check code yet; we'll check it later, because the
	// underlying closure function we create is added to Target.Decls.
	if ir.CurFunc != nil && clo.Type() != nil {
		oldfn := ir.CurFunc
		ir.CurFunc = fn
		Stmts(fn.Body)
		ir.CurFunc = oldfn
	}

	out := 0
	for _, v := range fn.ClosureVars {
		if v.Type() == nil {
			// If v.Type is nil, it means v looked like it was going to be
			// used in the closure, but isn't. This happens in struct
			// literals like s{f: x} where we can't distinguish whether f is
			// a field identifier or expression until resolving s.
			continue
		}

		// type check closed variables outside the closure, so that the
		// outer frame also captures them.
		Expr(v.Outer)

		fn.ClosureVars[out] = v
		out++
	}
	fn.ClosureVars = fn.ClosureVars[:out]

	if base.Flag.W > 1 {
		s := fmt.Sprintf("New closure func: %s", ir.FuncName(fn))
		ir.Dump(s, fn)
	}
	if !inTypeCheckInl {
		// Add function to Target.Decls once only when we give it a name
		Target.Decls = append(Target.Decls, fn)
	}
}

// type check function definition
// To be called by typecheck, not directly.
// (Call typecheck.Func instead.)
func tcFunc(n *ir.Func) {
	if base.EnableTrace && base.Flag.LowerT {
		defer tracePrint("tcFunc", n)(nil)
	}

	n.Nname = AssignExpr(n.Nname).(*ir.Name)
	t := n.Nname.Type()
	if t == nil {
		return
	}
	rcvr := t.Recv()
	if rcvr != nil && n.Shortname != nil {
		m := addmethod(n, n.Shortname, t, true, n.Pragma&ir.Nointerface != 0)
		if m == nil {
			return
		}

		n.Nname.SetSym(ir.MethodSym(rcvr.Type, n.Shortname))
		Declare(n.Nname, ir.PFUNC)
	}
}

// tcCall typechecks an OCALL node.
func tcCall(n *ir.CallExpr, top int) ir.Node {
	n.Use = ir.CallUseExpr
	if top == ctxStmt {
		n.Use = ir.CallUseStmt
	}
	Stmts(n.Init()) // imported rewritten f(g()) calls (#30907)
	n.X = typecheck(n.X, ctxExpr|ctxType|ctxCallee)
	if n.X.Diag() {
		n.SetDiag(true)
	}

	l := n.X

	if l.Op() == ir.ONAME && l.(*ir.Name).BuiltinOp != 0 {
		l := l.(*ir.Name)
		if n.IsDDD && l.BuiltinOp != ir.OAPPEND {
			base.Errorf("invalid use of ... with builtin %v", l)
		}

		// builtin: OLEN, OCAP, etc.
		switch l.BuiltinOp {
		default:
			base.Fatalf("unknown builtin %v", l)

		case ir.OAPPEND, ir.ODELETE, ir.OMAKE, ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
			n.SetOp(l.BuiltinOp)
			n.X = nil
			n.SetTypecheck(0) // re-typechecking new op is OK, not a loop
			return typecheck(n, top)

		case ir.OCAP, ir.OCLOSE, ir.OIMAG, ir.OLEN, ir.OPANIC, ir.OREAL:
			typecheckargs(n)
			fallthrough
		case ir.ONEW, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
			arg, ok := needOneArg(n, "%v", n.Op())
			if !ok {
				n.SetType(nil)
				return n
			}
			u := ir.NewUnaryExpr(n.Pos(), l.BuiltinOp, arg)
			return typecheck(ir.InitExpr(n.Init(), u), top) // typecheckargs can add to old.Init

		case ir.OCOMPLEX, ir.OCOPY, ir.OUNSAFEADD, ir.OUNSAFESLICE:
			typecheckargs(n)
			arg1, arg2, ok := needTwoArgs(n)
			if !ok {
				n.SetType(nil)
				return n
			}
			b := ir.NewBinaryExpr(n.Pos(), l.BuiltinOp, arg1, arg2)
			return typecheck(ir.InitExpr(n.Init(), b), top) // typecheckargs can add to old.Init
		}
		panic("unreachable")
	}

	n.X = DefaultLit(n.X, nil)
	l = n.X
	if l.Op() == ir.OTYPE {
		if n.IsDDD {
			if !l.Type().Broke() {
				base.Errorf("invalid use of ... in type conversion to %v", l.Type())
			}
			n.SetDiag(true)
		}

		// pick off before type-checking arguments
		arg, ok := needOneArg(n, "conversion to %v", l.Type())
		if !ok {
			n.SetType(nil)
			return n
		}

		n := ir.NewConvExpr(n.Pos(), ir.OCONV, nil, arg)
		n.SetType(l.Type())
		return tcConv(n)
	}

	typecheckargs(n)
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	types.CheckSize(t)

	switch l.Op() {
	case ir.ODOTINTER:
		n.SetOp(ir.OCALLINTER)

	case ir.ODOTMETH:
		l := l.(*ir.SelectorExpr)
		n.SetOp(ir.OCALLMETH)

		// typecheckaste was used here but there wasn't enough
		// information further down the call chain to know if we
		// were testing a method receiver for unexported fields.
		// It isn't necessary, so just do a sanity check.
		tp := t.Recv().Type

		if l.X == nil || !types.Identical(l.X.Type(), tp) {
			base.Fatalf("method receiver")
		}

	default:
		n.SetOp(ir.OCALLFUNC)
		if t.Kind() != types.TFUNC {
			if o := ir.Orig(l); o.Name() != nil && types.BuiltinPkg.Lookup(o.Sym().Name).Def != nil {
				// be more specific when the non-function
				// name matches a predeclared function
				base.Errorf("cannot call non-function %L, declared at %s",
					l, base.FmtPos(o.Name().Pos()))
			} else {
				base.Errorf("cannot call non-function %L", l)
			}
			n.SetType(nil)
			return n
		}
	}

	typecheckaste(ir.OCALL, n.X, n.IsDDD, t.Params(), n.Args, func() string { return fmt.Sprintf("argument to %v", n.X) })
	if t.NumResults() == 0 {
		return n
	}
	if t.NumResults() == 1 {
		n.SetType(l.Type().Results().Field(0).Type)

		if n.Op() == ir.OCALLFUNC && n.X.Op() == ir.ONAME {
			if sym := n.X.(*ir.Name).Sym(); types.IsRuntimePkg(sym.Pkg) && sym.Name == "getg" {
				// Emit code for runtime.getg() directly instead of calling function.
				// Most such rewrites (for example the similar one for math.Sqrt) should be done in walk,
				// so that the ordering pass can make sure to preserve the semantics of the original code
				// (in particular, the exact time of the function call) by introducing temporaries.
				// In this case, we know getg() always returns the same result within a given function
				// and we want to avoid the temporaries, so we do the rewrite earlier than is typical.
				n.SetOp(ir.OGETG)
			}
		}
		return n
	}

	// multiple return
	if top&(ctxMultiOK|ctxStmt) == 0 {
		base.Errorf("multiple-value %v() in single-value context", l)
		return n
	}

	n.SetType(l.Type().Results())
	return n
}

// tcAppend typechecks an OAPPEND node.
func tcAppend(n *ir.CallExpr) ir.Node {
	typecheckargs(n)
	args := n.Args
	if len(args) == 0 {
		base.Errorf("missing arguments to append")
		n.SetType(nil)
		return n
	}

	t := args[0].Type()
	if t == nil {
		n.SetType(nil)
		return n
	}

	n.SetType(t)
	if !t.IsSlice() {
		if ir.IsNil(args[0]) {
			base.Errorf("first argument to append must be typed slice; have untyped nil")
			n.SetType(nil)
			return n
		}

		base.Errorf("first argument to append must be slice; have %L", t)
		n.SetType(nil)
		return n
	}

	if n.IsDDD {
		if len(args) == 1 {
			base.Errorf("cannot use ... on first argument to append")
			n.SetType(nil)
			return n
		}

		if len(args) != 2 {
			base.Errorf("too many arguments to append")
			n.SetType(nil)
			return n
		}

		if t.Elem().IsKind(types.TUINT8) && args[1].Type().IsString() {
			args[1] = DefaultLit(args[1], types.Types[types.TSTRING])
			return n
		}

		args[1] = AssignConv(args[1], t.Underlying(), "append")
		return n
	}

	as := args[1:]
	for i, n := range as {
		if n.Type() == nil {
			continue
		}
		as[i] = AssignConv(n, t.Elem(), "append")
		types.CheckSize(as[i].Type()) // ensure width is calculated for backend
	}
	return n
}

// tcClose typechecks an OCLOSE node.
func tcClose(n *ir.UnaryExpr) ir.Node {
	n.X = Expr(n.X)
	n.X = DefaultLit(n.X, nil)
	l := n.X
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	if !t.IsChan() {
		base.Errorf("invalid operation: %v (non-chan type %v)", n, t)
		n.SetType(nil)
		return n
	}

	if !t.ChanDir().CanSend() {
		base.Errorf("invalid operation: %v (cannot close receive-only channel)", n)
		n.SetType(nil)
		return n
	}
	return n
}

// tcComplex typechecks an OCOMPLEX node.
func tcComplex(n *ir.BinaryExpr) ir.Node {
	l := Expr(n.X)
	r := Expr(n.Y)
	if l.Type() == nil || r.Type() == nil {
		n.SetType(nil)
		return n
	}
	l, r = defaultlit2(l, r, false)
	if l.Type() == nil || r.Type() == nil {
		n.SetType(nil)
		return n
	}
	n.X = l
	n.Y = r

	if !types.Identical(l.Type(), r.Type()) {
		base.Errorf("invalid operation: %v (mismatched types %v and %v)", n, l.Type(), r.Type())
		n.SetType(nil)
		return n
	}

	var t *types.Type
	switch l.Type().Kind() {
	default:
		base.Errorf("invalid operation: %v (arguments have type %v, expected floating-point)", n, l.Type())
		n.SetType(nil)
		return n

	case types.TIDEAL:
		t = types.UntypedComplex

	case types.TFLOAT32:
		t = types.Types[types.TCOMPLEX64]

	case types.TFLOAT64:
		t = types.Types[types.TCOMPLEX128]
	}
	n.SetType(t)
	return n
}

// tcCopy typechecks an OCOPY node.
func tcCopy(n *ir.BinaryExpr) ir.Node {
	n.SetType(types.Types[types.TINT])
	n.X = Expr(n.X)
	n.X = DefaultLit(n.X, nil)
	n.Y = Expr(n.Y)
	n.Y = DefaultLit(n.Y, nil)
	if n.X.Type() == nil || n.Y.Type() == nil {
		n.SetType(nil)
		return n
	}

	// copy([]byte, string)
	if n.X.Type().IsSlice() && n.Y.Type().IsString() {
		if types.Identical(n.X.Type().Elem(), types.ByteType) {
			return n
		}
		base.Errorf("arguments to copy have different element types: %L and string", n.X.Type())
		n.SetType(nil)
		return n
	}

	if !n.X.Type().IsSlice() || !n.Y.Type().IsSlice() {
		if !n.X.Type().IsSlice() && !n.Y.Type().IsSlice() {
			base.Errorf("arguments to copy must be slices; have %L, %L", n.X.Type(), n.Y.Type())
		} else if !n.X.Type().IsSlice() {
			base.Errorf("first argument to copy should be slice; have %L", n.X.Type())
		} else {
			base.Errorf("second argument to copy should be slice or string; have %L", n.Y.Type())
		}
		n.SetType(nil)
		return n
	}

	if !types.Identical(n.X.Type().Elem(), n.Y.Type().Elem()) {
		base.Errorf("arguments to copy have different element types: %L and %L", n.X.Type(), n.Y.Type())
		n.SetType(nil)
		return n
	}
	return n
}

// tcDelete typechecks an ODELETE node.
func tcDelete(n *ir.CallExpr) ir.Node {
	typecheckargs(n)
	args := n.Args
	if len(args) == 0 {
		base.Errorf("missing arguments to delete")
		n.SetType(nil)
		return n
	}

	if len(args) == 1 {
		base.Errorf("missing second (key) argument to delete")
		n.SetType(nil)
		return n
	}

	if len(args) != 2 {
		base.Errorf("too many arguments to delete")
		n.SetType(nil)
		return n
	}

	l := args[0]
	r := args[1]
	if l.Type() != nil && !l.Type().IsMap() {
		base.Errorf("first argument to delete must be map; have %L", l.Type())
		n.SetType(nil)
		return n
	}

	args[1] = AssignConv(r, l.Type().Key(), "delete")
	return n
}

// tcMake typechecks an OMAKE node.
func tcMake(n *ir.CallExpr) ir.Node {
	args := n.Args
	if len(args) == 0 {
		base.Errorf("missing argument to make")
		n.SetType(nil)
		return n
	}

	n.Args = nil
	l := args[0]
	l = typecheck(l, ctxType)
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}

	i := 1
	var nn ir.Node
	switch t.Kind() {
	default:
		base.Errorf("cannot make type %v", t)
		n.SetType(nil)
		return n

	case types.TSLICE:
		if i >= len(args) {
			base.Errorf("missing len argument to make(%v)", t)
			n.SetType(nil)
			return n
		}

		l = args[i]
		i++
		l = Expr(l)
		var r ir.Node
		if i < len(args) {
			r = args[i]
			i++
			r = Expr(r)
		}

		if l.Type() == nil || (r != nil && r.Type() == nil) {
			n.SetType(nil)
			return n
		}
		if !checkmake(t, "len", &l) || r != nil && !checkmake(t, "cap", &r) {
			n.SetType(nil)
			return n
		}
		if ir.IsConst(l, constant.Int) && r != nil && ir.IsConst(r, constant.Int) && constant.Compare(l.Val(), token.GTR, r.Val()) {
			base.Errorf("len larger than cap in make(%v)", t)
			n.SetType(nil)
			return n
		}
		nn = ir.NewMakeExpr(n.Pos(), ir.OMAKESLICE, l, r)

	case types.TMAP:
		if i < len(args) {
			l = args[i]
			i++
			l = Expr(l)
			l = DefaultLit(l, types.Types[types.TINT])
			if l.Type() == nil {
				n.SetType(nil)
				return n
			}
			if !checkmake(t, "size", &l) {
				n.SetType(nil)
				return n
			}
		} else {
			l = ir.NewInt(0)
		}
		nn = ir.NewMakeExpr(n.Pos(), ir.OMAKEMAP, l, nil)
		nn.SetEsc(n.Esc())

	case types.TCHAN:
		l = nil
		if i < len(args) {
			l = args[i]
			i++
			l = Expr(l)
			l = DefaultLit(l, types.Types[types.TINT])
			if l.Type() == nil {
				n.SetType(nil)
				return n
			}
			if !checkmake(t, "buffer", &l) {
				n.SetType(nil)
				return n
			}
		} else {
			l = ir.NewInt(0)
		}
		nn = ir.NewMakeExpr(n.Pos(), ir.OMAKECHAN, l, nil)
	}

	if i < len(args) {
		base.Errorf("too many arguments to make(%v)", t)
		n.SetType(nil)
		return n
	}

	nn.SetType(t)
	return nn
}

// tcMakeSliceCopy typechecks an OMAKESLICECOPY node.
func tcMakeSliceCopy(n *ir.MakeExpr) ir.Node {
	// Errors here are Fatalf instead of Errorf because only the compiler
	// can construct an OMAKESLICECOPY node.
	// Components used in OMAKESCLICECOPY that are supplied by parsed source code
	// have already been typechecked in OMAKE and OCOPY earlier.
	t := n.Type()

	if t == nil {
		base.Fatalf("no type specified for OMAKESLICECOPY")
	}

	if !t.IsSlice() {
		base.Fatalf("invalid type %v for OMAKESLICECOPY", n.Type())
	}

	if n.Len == nil {
		base.Fatalf("missing len argument for OMAKESLICECOPY")
	}

	if n.Cap == nil {
		base.Fatalf("missing slice argument to copy for OMAKESLICECOPY")
	}

	n.Len = Expr(n.Len)
	n.Cap = Expr(n.Cap)

	n.Len = DefaultLit(n.Len, types.Types[types.TINT])

	if !n.Len.Type().IsInteger() && n.Type().Kind() != types.TIDEAL {
		base.Errorf("non-integer len argument in OMAKESLICECOPY")
	}

	if ir.IsConst(n.Len, constant.Int) {
		if ir.ConstOverflow(n.Len.Val(), types.Types[types.TINT]) {
			base.Fatalf("len for OMAKESLICECOPY too large")
		}
		if constant.Sign(n.Len.Val()) < 0 {
			base.Fatalf("len for OMAKESLICECOPY must be non-negative")
		}
	}
	return n
}

// tcNew typechecks an ONEW node.
func tcNew(n *ir.UnaryExpr) ir.Node {
	if n.X == nil {
		// Fatalf because the OCALL above checked for us,
		// so this must be an internally-generated mistake.
		base.Fatalf("missing argument to new")
	}
	l := n.X
	l = typecheck(l, ctxType)
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	n.X = l
	n.SetType(types.NewPtr(t))
	return n
}

// tcPanic typechecks an OPANIC node.
func tcPanic(n *ir.UnaryExpr) ir.Node {
	n.X = Expr(n.X)
	n.X = AssignConv(n.X, types.Types[types.TINTER], "argument to panic")
	if n.X.Type() == nil {
		n.SetType(nil)
		return n
	}
	return n
}

// tcPrint typechecks an OPRINT or OPRINTN node.
func tcPrint(n *ir.CallExpr) ir.Node {
	typecheckargs(n)
	ls := n.Args
	for i1, n1 := range ls {
		// Special case for print: int constant is int64, not int.
		if ir.IsConst(n1, constant.Int) {
			ls[i1] = DefaultLit(ls[i1], types.Types[types.TINT64])
		} else {
			ls[i1] = DefaultLit(ls[i1], nil)
		}
	}
	return n
}

// tcRealImag typechecks an OREAL or OIMAG node.
func tcRealImag(n *ir.UnaryExpr) ir.Node {
	n.X = Expr(n.X)
	l := n.X
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}

	// Determine result type.
	switch t.Kind() {
	case types.TIDEAL:
		n.SetType(types.UntypedFloat)
	case types.TCOMPLEX64:
		n.SetType(types.Types[types.TFLOAT32])
	case types.TCOMPLEX128:
		n.SetType(types.Types[types.TFLOAT64])
	default:
		base.Errorf("invalid argument %L for %v", l, n.Op())
		n.SetType(nil)
		return n
	}
	return n
}

// tcRecover typechecks an ORECOVER node.
func tcRecover(n *ir.CallExpr) ir.Node {
	if len(n.Args) != 0 {
		base.Errorf("too many arguments to recover")
		n.SetType(nil)
		return n
	}

	n.SetType(types.Types[types.TINTER])
	return n
}

// tcUnsafeAdd typechecks an OUNSAFEADD node.
func tcUnsafeAdd(n *ir.BinaryExpr) *ir.BinaryExpr {
	if !types.AllowsGoVersion(curpkg(), 1, 17) {
		base.ErrorfVers("go1.17", "unsafe.Add")
		n.SetType(nil)
		return n
	}

	n.X = AssignConv(Expr(n.X), types.Types[types.TUNSAFEPTR], "argument to unsafe.Add")
	n.Y = DefaultLit(Expr(n.Y), types.Types[types.TINT])
	if n.X.Type() == nil || n.Y.Type() == nil {
		n.SetType(nil)
		return n
	}
	if !n.Y.Type().IsInteger() {
		n.SetType(nil)
		return n
	}
	n.SetType(n.X.Type())
	return n
}

// tcUnsafeSlice typechecks an OUNSAFESLICE node.
func tcUnsafeSlice(n *ir.BinaryExpr) *ir.BinaryExpr {
	if !types.AllowsGoVersion(curpkg(), 1, 17) {
		base.ErrorfVers("go1.17", "unsafe.Slice")
		n.SetType(nil)
		return n
	}

	n.X = Expr(n.X)
	n.Y = Expr(n.Y)
	if n.X.Type() == nil || n.Y.Type() == nil {
		n.SetType(nil)
		return n
	}
	t := n.X.Type()
	if !t.IsPtr() {
		base.Errorf("first argument to unsafe.Slice must be pointer; have %L", t)
	} else if t.Elem().NotInHeap() {
		// TODO(mdempsky): This can be relaxed, but should only affect the
		// Go runtime itself. End users should only see //go:notinheap
		// types due to incomplete C structs in cgo, and those types don't
		// have a meaningful size anyway.
		base.Errorf("unsafe.Slice of incomplete (or unallocatable) type not allowed")
	}

	if !checkunsafeslice(&n.Y) {
		n.SetType(nil)
		return n
	}
	n.SetType(types.NewSlice(t.Elem()))
	return n
}