golang builtins 代码
文件路径：/src/go/types/builtins.go
/ Copyright 2012 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.
/ This file implements typechecking of builtin function calls.
package types
import (
"go/ast"
"go/constant"
"go/token"
)
/ builtin type-checks a call to the built-in specified by id and
/ reports whether the call is valid, with *x holding the result;
/ but x.expr is not set. If the call is invalid, the result is
/ false, and *x is undefined.
func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ bool) {
/ append is the only built-in that permits the use of ... for the last argument
bin := predeclaredFuncs[id]
if call.Ellipsis.IsValid() && id != _Append {
check.invalidOp(atPos(call.Ellipsis),
_InvalidDotDotDot,
"invalid use of ... with built-in %s", bin.name)
check.use(call.Args...)
return
}
/ For len(x) and cap(x) we need to know if x contains any function calls or
/ receive operations. Save/restore current setting and set hasCallOrRecv to
/ false for the evaluation of x so that we can check it afterwards.
/ Note: We must do this _before_ calling exprList because exprList evaluates
/ all arguments.
if id == _Len || id == _Cap {
defer func(b bool) {
check.hasCallOrRecv = b
}(check.hasCallOrRecv)
check.hasCallOrRecv = false
}
/ determine actual arguments
var arg func(*operand, int) / TODO(gri) remove use of arg getter in favor of using xlist directly
nargs := len(call.Args)
switch id {
default:
/ make argument getter
xlist, _ := check.exprList(call.Args, false)
arg = func(x *operand, i int) { *x = *xlist[i] }
nargs = len(xlist)
/ evaluate first argument, if present
if nargs > 0 {
arg(x, 0)
if x.mode == invalid {
return
}
}
case _Make, _New, _Offsetof, _Trace:
/ arguments require special handling
}
/ check argument count
{
msg := ""
if nargs < bin.nargs {
msg = "not enough"
} else if !bin.variadic && nargs > bin.nargs {
msg = "too many"
}
if msg != "" {
check.invalidOp(inNode(call, call.Rparen), _WrongArgCount, "%s arguments for %s (expected %d, found %d)", msg, call, bin.nargs, nargs)
return
}
}
switch id {
case _Append:
/ append(s S, x ...T) S, where T is the element type of S
/ spec: "The variadic function append appends zero or more values x to s of type
/ S, which must be a slice type, and returns the resulting slice, also of type S.
/ The values x are passed to a parameter of type ...T where T is the element type
/ of S and the respective parameter passing rules apply."
S := x.typ
var T Type
if s, _ := coreType(S).(*Slice); s != nil {
T = s.elem
} else {
var cause string
switch {
case x.isNil():
cause = "have untyped nil"
case isTypeParam(S):
if u := coreType(S); u != nil {
cause = check.sprintf("%s has core type %s", x, u)
} else {
cause = check.sprintf("%s has no core type", x)
}
default:
cause = check.sprintf("have %s", x)
}
/ don't use Checker.invalidArg here as it would repeat "argument" in the error message
check.errorf(x, _InvalidAppend, "first argument to append must be a slice; %s", cause)
return
}
/ remember arguments that have been evaluated already
alist := []operand{*x}
/ spec: "As a special case, append also accepts a first argument assignable
/ to type []byte with a second argument of string type followed by ... .
/ This form appends the bytes of the string.
if nargs == 2 && call.Ellipsis.IsValid() {
if ok, _ := x.assignableTo(check, NewSlice(universeByte), nil); ok {
arg(x, 1)
if x.mode == invalid {
return
}
if t := coreString(x.typ); t != nil && isString(t) {
if check.Types != nil {
sig := makeSig(S, S, x.typ)
sig.variadic = true
check.recordBuiltinType(call.Fun, sig)
}
x.mode = value
x.typ = S
break
}
alist = append(alist, *x)
/ fallthrough
}
}
/ check general case by creating custom signature
sig := makeSig(S, S, NewSlice(T)) / []T required for variadic signature
sig.variadic = true
var xlist []*operand
/ convert []operand to []*operand
for i := range alist {
xlist = append(xlist, &alist[i])
}
for i := len(alist); i < nargs; i++ {
var x operand
arg(&x, i)
xlist = append(xlist, &x)
}
check.arguments(call, sig, nil, xlist, nil) / discard result (we know the result type)
/ ok to continue even if check.arguments reported errors
x.mode = value
x.typ = S
if check.Types != nil {
check.recordBuiltinType(call.Fun, sig)
}
case _Cap, _Len:
/ cap(x)
/ len(x)
mode := invalid
var val constant.Value
switch t := arrayPtrDeref(under(x.typ)).(type) {
case *Basic:
if isString(t) && id == _Len {
if x.mode == constant_ {
mode = constant_
val = constant.MakeInt64(int64(len(constant.StringVal(x.val))))
} else {
mode = value
}
}
case *Array:
mode = value
/ spec: "The expressions len(s) and cap(s) are constants
/ if the type of s is an array or pointer to an array and
/ the expression s does not contain channel receives or
/ function calls; in this case s is not evaluated."
if !check.hasCallOrRecv {
mode = constant_
if t.len >= 0 {
val = constant.MakeInt64(t.len)
} else {
val = constant.MakeUnknown()
}
}
case *Slice, *Chan:
mode = value
case *Map:
if id == _Len {
mode = value
}
case *Interface:
if !isTypeParam(x.typ) {
break
}
if t.typeSet().underIs(func(t Type) bool {
switch t := arrayPtrDeref(t).(type) {
case *Basic:
if isString(t) && id == _Len {
return true
}
case *Array, *Slice, *Chan:
return true
case *Map:
if id == _Len {
return true
}
}
return false
}) {
mode = value
}
}
if mode == invalid && under(x.typ) != Typ[Invalid] {
code := _InvalidCap
if id == _Len {
code = _InvalidLen
}
check.invalidArg(x, code, "%s for %s", x, bin.name)
return
}
/ record the signature before changing x.typ
if check.Types != nil && mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(Typ[Int], x.typ))
}
x.mode = mode
x.typ = Typ[Int]
x.val = val
case _Close:
/ close(c)
if !underIs(x.typ, func(u Type) bool {
uch, _ := u.(*Chan)
if uch == nil {
check.invalidOp(x, _InvalidClose, "cannot close non-channel %s", x)
return false
}
if uch.dir == RecvOnly {
check.invalidOp(x, _InvalidClose, "cannot close receive-only channel %s", x)
return false
}
return true
}) {
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, x.typ))
}
case _Complex:
/ complex(x, y floatT) complexT
var y operand
arg(&y, 1)
if y.mode == invalid {
return
}
/ convert or check untyped arguments
d := 0
if isUntyped(x.typ) {
d |= 1
}
if isUntyped(y.typ) {
d |= 2
}
switch d {
case 0:
/ x and y are typed => nothing to do
case 1:
/ only x is untyped => convert to type of y
check.convertUntyped(x, y.typ)
case 2:
/ only y is untyped => convert to type of x
check.convertUntyped(&y, x.typ)
case 3:
/ x and y are untyped =>
/ 1) if both are constants, convert them to untyped
/ floating-point numbers if possible,
/ 2) if one of them is not constant (possible because
/ it contains a shift that is yet untyped), convert
/ both of them to float64 since they must have the
/ same type to succeed (this will result in an error
/ because shifts of floats are not permitted)
if x.mode == constant_ && y.mode == constant_ {
toFloat := func(x *operand) {
if isNumeric(x.typ) && constant.Sign(constant.Imag(x.val)) == 0 {
x.typ = Typ[UntypedFloat]
}
}
toFloat(x)
toFloat(&y)
} else {
check.convertUntyped(x, Typ[Float64])
check.convertUntyped(&y, Typ[Float64])
/ x and y should be invalid now, but be conservative
/ and check below
}
}
if x.mode == invalid || y.mode == invalid {
return
}
/ both argument types must be identical
if !Identical(x.typ, y.typ) {
check.invalidArg(x, _InvalidComplex, "mismatched types %s and %s", x.typ, y.typ)
return
}
/ the argument types must be of floating-point type
/ (applyTypeFunc never calls f with a type parameter)
f := func(typ Type) Type {
assert(!isTypeParam(typ))
if t, _ := under(typ).(*Basic); t != nil {
switch t.kind {
case Float32:
return Typ[Complex64]
case Float64:
return Typ[Complex128]
case UntypedFloat:
return Typ[UntypedComplex]
}
}
return nil
}
resTyp := check.applyTypeFunc(f, x, id)
if resTyp == nil {
check.invalidArg(x, _InvalidComplex, "arguments have type %s, expected floating-point", x.typ)
return
}
/ if both arguments are constants, the result is a constant
if x.mode == constant_ && y.mode == constant_ {
x.val = constant.BinaryOp(constant.ToFloat(x.val), token.ADD, constant.MakeImag(constant.ToFloat(y.val)))
} else {
x.mode = value
}
if check.Types != nil && x.mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(resTyp, x.typ, x.typ))
}
x.typ = resTyp
case _Copy:
/ copy(x, y []T) int
dst, _ := coreType(x.typ).(*Slice)
var y operand
arg(&y, 1)
if y.mode == invalid {
return
}
src0 := coreString(y.typ)
if src0 != nil && isString(src0) {
src0 = NewSlice(universeByte)
}
src, _ := src0.(*Slice)
if dst == nil || src == nil {
check.invalidArg(x, _InvalidCopy, "copy expects slice arguments; found %s and %s", x, &y)
return
}
if !Identical(dst.elem, src.elem) {
check.errorf(x, _InvalidCopy, "arguments to copy %s and %s have different element types %s and %s", x, &y, dst.elem, src.elem)
return
}
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(Typ[Int], x.typ, y.typ))
}
x.mode = value
x.typ = Typ[Int]
case _Delete:
/ delete(map_, key)
/ map_ must be a map type or a type parameter describing map types.
/ The key cannot be a type parameter for now.
map_ := x.typ
var key Type
if !underIs(map_, func(u Type) bool {
map_, _ := u.(*Map)
if map_ == nil {
check.invalidArg(x, _InvalidDelete, "%s is not a map", x)
return false
}
if key != nil && !Identical(map_.key, key) {
check.invalidArg(x, _InvalidDelete, "maps of %s must have identical key types", x)
return false
}
key = map_.key
return true
}) {
return
}
arg(x, 1) / k
if x.mode == invalid {
return
}
check.assignment(x, key, "argument to delete")
if x.mode == invalid {
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, map_, key))
}
case _Imag, _Real:
/ imag(complexT) floatT
/ real(complexT) floatT
/ convert or check untyped argument
if isUntyped(x.typ) {
if x.mode == constant_ {
/ an untyped constant number can always be considered
/ as a complex constant
if isNumeric(x.typ) {
x.typ = Typ[UntypedComplex]
}
} else {
/ an untyped non-constant argument may appear if
/ it contains a (yet untyped non-constant) shift
/ expression: convert it to complex128 which will
/ result in an error (shift of complex value)
check.convertUntyped(x, Typ[Complex128])
/ x should be invalid now, but be conservative and check
if x.mode == invalid {
return
}
}
}
/ the argument must be of complex type
/ (applyTypeFunc never calls f with a type parameter)
f := func(typ Type) Type {
assert(!isTypeParam(typ))
if t, _ := under(typ).(*Basic); t != nil {
switch t.kind {
case Complex64:
return Typ[Float32]
case Complex128:
return Typ[Float64]
case UntypedComplex:
return Typ[UntypedFloat]
}
}
return nil
}
resTyp := check.applyTypeFunc(f, x, id)
if resTyp == nil {
code := _InvalidImag
if id == _Real {
code = _InvalidReal
}
check.invalidArg(x, code, "argument has type %s, expected complex type", x.typ)
return
}
/ if the argument is a constant, the result is a constant
if x.mode == constant_ {
if id == _Real {
x.val = constant.Real(x.val)
} else {
x.val = constant.Imag(x.val)
}
} else {
x.mode = value
}
if check.Types != nil && x.mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(resTyp, x.typ))
}
x.typ = resTyp
case _Make:
/ make(T, n)
/ make(T, n, m)
/ (no argument evaluated yet)
arg0 := call.Args[0]
T := check.varType(arg0)
if T == Typ[Invalid] {
return
}
var min int / minimum number of arguments
switch coreType(T).(type) {
case *Slice:
min = 2
case *Map, *Chan:
min = 1
case nil:
check.errorf(arg0, _InvalidMake, "cannot make %s: no core type", arg0)
return
default:
check.invalidArg(arg0, _InvalidMake, "cannot make %s; type must be slice, map, or channel", arg0)
return
}
if nargs < min || min+1 < nargs {
check.invalidOp(call, _WrongArgCount, "%v expects %d or %d arguments; found %d", call, min, min+1, nargs)
return
}
types := []Type{T}
var sizes []int64 / constant integer arguments, if any
for _, arg := range call.Args[1:] {
typ, size := check.index(arg, -1) / ok to continue with typ == Typ[Invalid]
types = append(types, typ)
if size >= 0 {
sizes = append(sizes, size)
}
}
if len(sizes) == 2 && sizes[0] > sizes[1] {
check.invalidArg(call.Args[1], _SwappedMakeArgs, "length and capacity swapped")
/ safe to continue
}
x.mode = value
x.typ = T
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ, types...))
}
case _New:
/ new(T)
/ (no argument evaluated yet)
T := check.varType(call.Args[0])
if T == Typ[Invalid] {
return
}
x.mode = value
x.typ = &Pointer{base: T}
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ, T))
}
case _Panic:
/ panic(x)
/ record panic call if inside a function with result parameters
/ (for use in Checker.isTerminating)
if check.sig != nil && check.sig.results.Len() > 0 {
/ function has result parameters
p := check.isPanic
if p == nil {
/ allocate lazily
p = make(map[*ast.CallExpr]bool)
check.isPanic = p
}
p[call] = true
}
check.assignment(x, &emptyInterface, "argument to panic")
if x.mode == invalid {
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, &emptyInterface))
}
case _Print, _Println:
/ print(x, y, ...)
/ println(x, y, ...)
var params []Type
if nargs > 0 {
params = make([]Type, nargs)
for i := 0; i < nargs; i++ {
if i > 0 {
arg(x, i) / first argument already evaluated
}
check.assignment(x, nil, "argument to "+predeclaredFuncs[id].name)
if x.mode == invalid {
/ TODO(gri) "use" all arguments?
return
}
params[i] = x.typ
}
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, params...))
}
case _Recover:
/ recover() interface{}
x.mode = value
x.typ = &emptyInterface
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ))
}
case _Add:
/ unsafe.Add(ptr unsafe.Pointer, len IntegerType) unsafe.Pointer
if !check.allowVersion(check.pkg, 1, 17) {
check.errorf(call.Fun, _InvalidUnsafeAdd, "unsafe.Add requires go1.17 or later")
return
}
check.assignment(x, Typ[UnsafePointer], "argument to unsafe.Add")
if x.mode == invalid {
return
}
var y operand
arg(&y, 1)
if !check.isValidIndex(&y, _InvalidUnsafeAdd, "length", true) {
return
}
x.mode = value
x.typ = Typ[UnsafePointer]
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ, x.typ, y.typ))
}
case _Alignof:
/ unsafe.Alignof(x T) uintptr
check.assignment(x, nil, "argument to unsafe.Alignof")
if x.mode == invalid {
return
}
if hasVarSize(x.typ, nil) {
x.mode = value
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], x.typ))
}
} else {
x.mode = constant_
x.val = constant.MakeInt64(check.conf.alignof(x.typ))
/ result is constant - no need to record signature
}
x.typ = Typ[Uintptr]
case _Offsetof:
/ unsafe.Offsetof(x T) uintptr, where x must be a selector
/ (no argument evaluated yet)
arg0 := call.Args[0]
selx, _ := unparen(arg0).(*ast.SelectorExpr)
if selx == nil {
check.invalidArg(arg0, _BadOffsetofSyntax, "%s is not a selector expression", arg0)
check.use(arg0)
return
}
check.expr(x, selx.X)
if x.mode == invalid {
return
}
base := derefStructPtr(x.typ)
sel := selx.Sel.Name
obj, index, indirect := LookupFieldOrMethod(base, false, check.pkg, sel)
switch obj.(type) {
case nil:
check.invalidArg(x, _MissingFieldOrMethod, "%s has no single field %s", base, sel)
return
case *Func:
/ TODO(gri) Using derefStructPtr may result in methods being found
/ that don't actually exist. An error either way, but the error
/ message is confusing. See: https://play.golang.org/p/al75v23kUy ,
/ but go/types reports: "invalid argument: x.m is a method value".
check.invalidArg(arg0, _InvalidOffsetof, "%s is a method value", arg0)
return
}
if indirect {
check.invalidArg(x, _InvalidOffsetof, "field %s is embedded via a pointer in %s", sel, base)
return
}
/ TODO(gri) Should we pass x.typ instead of base (and have indirect report if derefStructPtr indirected)?
check.recordSelection(selx, FieldVal, base, obj, index, false)
/ record the selector expression (was bug - issue #47895)
{
mode := value
if x.mode == variable || indirect {
mode = variable
}
check.record(&operand{mode, selx, obj.Type(), nil, 0})
}
/ The field offset is considered a variable even if the field is declared before
/ the part of the struct which is variable-sized. This makes both the rules
/ simpler and also permits (or at least doesn't prevent) a compiler from re-
/ arranging struct fields if it wanted to.
if hasVarSize(base, nil) {
x.mode = value
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], obj.Type()))
}
} else {
x.mode = constant_
x.val = constant.MakeInt64(check.conf.offsetof(base, index))
/ result is constant - no need to record signature
}
x.typ = Typ[Uintptr]
case _Sizeof:
/ unsafe.Sizeof(x T) uintptr
check.assignment(x, nil, "argument to unsafe.Sizeof")
if x.mode == invalid {
return
}
if hasVarSize(x.typ, nil) {
x.mode = value
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], x.typ))
}
} else {
x.mode = constant_
x.val = constant.MakeInt64(check.conf.sizeof(x.typ))
/ result is constant - no need to record signature
}
x.typ = Typ[Uintptr]
case _Slice:
/ unsafe.Slice(ptr *T, len IntegerType) []T
if !check.allowVersion(check.pkg, 1, 17) {
check.errorf(call.Fun, _InvalidUnsafeSlice, "unsafe.Slice requires go1.17 or later")
return
}
typ, _ := under(x.typ).(*Pointer)
if typ == nil {
check.invalidArg(x, _InvalidUnsafeSlice, "%s is not a pointer", x)
return
}
var y operand
arg(&y, 1)
if !check.isValidIndex(&y, _InvalidUnsafeSlice, "length", false) {
return
}
x.mode = value
x.typ = NewSlice(typ.base)
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ, typ, y.typ))
}
case _Assert:
/ assert(pred) causes a typechecker error if pred is false.
/ The result of assert is the value of pred if there is no error.
/ Note: assert is only available in self-test mode.
if x.mode != constant_ || !isBoolean(x.typ) {
check.invalidArg(x, _Test, "%s is not a boolean constant", x)
return
}
if x.val.Kind() != constant.Bool {
check.errorf(x, _Test, "internal error: value of %s should be a boolean constant", x)
return
}
if !constant.BoolVal(x.val) {
check.errorf(call, _Test, "%v failed", call)
/ compile-time assertion failure - safe to continue
}
/ result is constant - no need to record signature
case _Trace:
/ trace(x, y, z, ...) dumps the positions, expressions, and
/ values of its arguments. The result of trace is the value
/ of the first argument.
/ Note: trace is only available in self-test mode.
/ (no argument evaluated yet)
if nargs == 0 {
check.dump("%v: trace() without arguments", call.Pos())
x.mode = novalue
break
}
var t operand
x1 := x
for _, arg := range call.Args {
check.rawExpr(x1, arg, nil, false) / permit trace for types, e.g.: new(trace(T))
check.dump("%v: %s", x1.Pos(), x1)
x1 = &t / use incoming x only for first argument
}
/ trace is only available in test mode - no need to record signature
default:
unreachable()
}
return true
}
/ hasVarSize reports if the size of type t is variable due to type parameters
/ or if the type is infinitely-sized due to a cycle for which the type has not
/ yet been checked.
func hasVarSize(t Type, seen map[*Named]bool) (varSized bool) {
/ Cycles are only possible through *Named types.
/ The seen map is used to detect cycles and track
/ the results of previously seen types.
if named, _ := t.(*Named); named != nil {
if v, ok := seen[named]; ok {
return v
}
if seen == nil {
seen = make(map[*Named]bool)
}
seen[named] = true / possibly cyclic until proven otherwise
defer func() {
seen[named] = varSized / record final determination for named
}()
}
switch u := under(t).(type) {
case *Array:
return hasVarSize(u.elem, seen)
case *Struct:
for _, f := range u.fields {
if hasVarSize(f.typ, seen) {
return true
}
}
case *Interface:
return isTypeParam(t)
case *Named, *Union:
unreachable()
}
return false
}
/ applyTypeFunc applies f to x. If x is a type parameter,
/ the result is a type parameter constrained by an new
/ interface bound. The type bounds for that interface
/ are computed by applying f to each of the type bounds
/ of x. If any of these applications of f return nil,
/ applyTypeFunc returns nil.
/ If x is not a type parameter, the result is f(x).
func (check *Checker) applyTypeFunc(f func(Type) Type, x *operand, id builtinId) Type {
if tp, _ := x.typ.(*TypeParam); tp != nil {
/ Test if t satisfies the requirements for the argument
/ type and collect possible result types at the same time.
var terms []*Term
if !tp.is(func(t *term) bool {
if t == nil {
return false
}
if r := f(t.typ); r != nil {
terms = append(terms, NewTerm(t.tilde, r))
return true
}
return false
}) {
return nil
}
/ We can type-check this fine but we're introducing a synthetic
/ type parameter for the result. It's not clear what the API
/ implications are here. Report an error for 1.18 (see #50912),
/ but continue type-checking.
var code errorCode
switch id {
case _Real:
code = _InvalidReal
case _Imag:
code = _InvalidImag
case _Complex:
code = _InvalidComplex
default:
unreachable()
}
check.softErrorf(x, code, "%s not supported as argument to %s for go1.18 (see issue #50937)", x, predeclaredFuncs[id].name)
/ Construct a suitable new type parameter for the result type.
/ The type parameter is placed in the current package so export/import
/ works as expected.
tpar := NewTypeName(token.NoPos, check.pkg, tp.obj.name, nil)
ptyp := check.newTypeParam(tpar, NewInterfaceType(nil, []Type{NewUnion(terms)})) / assigns type to tpar as a side-effect
ptyp.index = tp.index
return ptyp
}
return f(x.typ)
}
/ makeSig makes a signature for the given argument and result types.
/ Default types are used for untyped arguments, and res may be nil.
func makeSig(res Type, args ...Type) *Signature {
list := make([]*Var, len(args))
for i, param := range args {
list[i] = NewVar(token.NoPos, nil, "", Default(param))
}
params := NewTuple(list...)
var result *Tuple
if res != nil {
assert(!isUntyped(res))
result = NewTuple(NewVar(token.NoPos, nil, "", res))
}
return &Signature{params: params, results: result}
}
/ arrayPtrDeref returns A if typ is of the form *A and A is an array;
/ otherwise it returns typ.
func arrayPtrDeref(typ Type) Type {
if p, ok := typ.(*Pointer); ok {
if a, _ := under(p.base).(*Array); a != nil {
return a
}
}
return typ
}
/ unparen returns e with any enclosing parentheses stripped.
func unparen(e ast.Expr) ast.Expr {
for {
p, ok := e.(*ast.ParenExpr)
if !ok {
return e
}
e = p.X
}
}