elvish/pkg/eval/closure.go
Kurtis Rader e2759f777b Initialize a command var to $nop~
You cannot assign $nil to a command var so that should not be the initial
value of `var x~`. Instead, assign $builtin:nop~.

Fixes #1248
2021-03-28 22:51:30 -07:00

203 lines
5.3 KiB
Go

package eval
import (
"fmt"
"sort"
"strconv"
"strings"
"unsafe"
"github.com/xiaq/persistent/hash"
"src.elv.sh/pkg/diag"
"src.elv.sh/pkg/eval/errs"
"src.elv.sh/pkg/eval/vals"
"src.elv.sh/pkg/eval/vars"
"src.elv.sh/pkg/parse"
)
// A user-defined function in Elvish code. Each closure has its unique identity.
type closure struct {
ArgNames []string
// The index of the rest argument. -1 if there is no rest argument.
RestArg int
OptNames []string
OptDefaults []interface{}
Op effectOp
NewLocal []string
Captured *Ns
SrcMeta parse.Source
DefRange diag.Ranging
}
var _ Callable = &closure{}
// Kind returns "fn".
func (*closure) Kind() string {
return "fn"
}
// Equal compares by address.
func (c *closure) Equal(rhs interface{}) bool {
return c == rhs
}
// Hash returns the hash of the address of the closure.
func (c *closure) Hash() uint32 {
return hash.Pointer(unsafe.Pointer(c))
}
// Repr returns an opaque representation "<closure 0x23333333>".
func (c *closure) Repr(int) string {
return fmt.Sprintf("<closure %p>", c)
}
// Call calls a closure.
func (c *closure) Call(fm *Frame, args []interface{}, opts map[string]interface{}) error {
// Check number of arguments.
if c.RestArg != -1 {
if len(args) < len(c.ArgNames)-1 {
return errs.ArityMismatch{
What: "arguments here",
ValidLow: len(c.ArgNames) - 1, ValidHigh: -1, Actual: len(args)}
}
} else {
if len(args) != len(c.ArgNames) {
return errs.ArityMismatch{
What: "arguments here",
ValidLow: len(c.ArgNames), ValidHigh: len(c.ArgNames), Actual: len(args)}
}
}
// Check whether all supplied options are supported. This map contains the
// subset of keys from opts that can be found in c.OptNames.
optSupported := make(map[string]struct{})
for _, name := range c.OptNames {
_, ok := opts[name]
if ok {
optSupported[name] = struct{}{}
}
}
if len(optSupported) < len(opts) {
// Report all the options that are not supported.
unsupported := make([]string, 0, len(opts)-len(optSupported))
for name := range opts {
_, supported := optSupported[name]
if !supported {
unsupported = append(unsupported, parse.Quote(name))
}
}
sort.Strings(unsupported)
return UnsupportedOptionsError{unsupported}
}
// This Frame is dedicated to the current form, so we can modify it in place.
// BUG(xiaq): When evaluating closures, async access to global variables
// and ports can be problematic.
// Make upvalue namespace and capture variables.
fm.up = c.Captured
// Populate local scope with arguments, options, and newly created locals.
localSize := len(c.ArgNames) + len(c.OptNames) + len(c.NewLocal)
local := &Ns{make([]vars.Var, localSize), make([]string, localSize), make([]bool, localSize)}
for i, name := range c.ArgNames {
local.names[i] = name
}
if c.RestArg == -1 {
for i := range c.ArgNames {
local.slots[i] = vars.FromInit(args[i])
}
} else {
for i := 0; i < c.RestArg; i++ {
local.slots[i] = vars.FromInit(args[i])
}
restOff := len(args) - len(c.ArgNames)
local.slots[c.RestArg] = vars.FromInit(
vals.MakeList(args[c.RestArg : c.RestArg+restOff+1]...))
for i := c.RestArg + 1; i < len(c.ArgNames); i++ {
local.slots[i] = vars.FromInit(args[i+restOff])
}
}
offset := len(c.ArgNames)
for i, name := range c.OptNames {
v, ok := opts[name]
if !ok {
v = c.OptDefaults[i]
}
local.names[offset+i] = name
local.slots[offset+i] = vars.FromInit(v)
}
offset += len(c.OptNames)
for i, name := range c.NewLocal {
local.names[offset+i] = name
local.slots[offset+i] = MakeVarFromName(name)
}
fm.local = local
fm.srcMeta = c.SrcMeta
return c.Op.exec(fm)
}
// MakeVarFromName creates a Var with a suitable type constraint inferred from
// the name.
func MakeVarFromName(name string) vars.Var {
switch {
case strings.HasSuffix(name, FnSuffix):
val := NewGoFn("nop~", nop)
return vars.FromPtr(&val)
case strings.HasSuffix(name, NsSuffix):
val := (*Ns)(nil)
return vars.FromPtr(&val)
default:
return vars.FromInit(nil)
}
}
// UnsupportedOptionsError is an error returned by a closure call when there are
// unsupported options.
type UnsupportedOptionsError struct {
Options []string
}
func (er UnsupportedOptionsError) Error() string {
if len(er.Options) == 1 {
return fmt.Sprintf("unsupported option: %s", er.Options[0])
}
return fmt.Sprintf("unsupported options: %s", strings.Join(er.Options, ", "))
}
func (c *closure) Fields() vals.StructMap { return closureFields{c} }
type closureFields struct{ c *closure }
func (closureFields) IsStructMap() {}
func (cf closureFields) ArgNames() vals.List { return listOfStrings(cf.c.ArgNames) }
func (cf closureFields) RestArg() string { return strconv.Itoa(cf.c.RestArg) }
func (cf closureFields) OptNames() vals.List { return listOfStrings(cf.c.OptNames) }
func (cf closureFields) Src() parse.Source { return cf.c.SrcMeta }
func (cf closureFields) OptDefaults() vals.List {
return vals.MakeList(cf.c.OptDefaults...)
}
func (cf closureFields) Body() string {
r := cf.c.Op.(diag.Ranger).Range()
return cf.c.SrcMeta.Code[r.From:r.To]
}
func (cf closureFields) Def() string {
return cf.c.SrcMeta.Code[cf.c.DefRange.From:cf.c.DefRange.To]
}
func listOfStrings(ss []string) vals.List {
list := vals.EmptyList
for _, s := range ss {
list = list.Cons(s)
}
return list
}