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go.tools/go/types: complete checking of append built-in

Browse Source 
R=adonovan
CC=golang-dev
https://golang.org/cl/14238043
This commit is contained in:
Robert Griesemer 2013-10-01 18:14:15 -07:00
parent d7d04a24e8
commit a32c2633d0
4 changed files with 163 additions and 70 deletions
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1
go/types/api.go
View File

@ -181,6 +181,5 @@ func IsAssignableTo(V, T Type) bool {
return x.isAssignableTo(nil, T) // config not needed for non-constant x
}
// BUG(gri): Some built-ins don't check parameters fully, yet (e.g. append).
// BUG(gri): Interface vs non-interface comparisons are not correctly implemented.
// BUG(gri): Switch statements don't check duplicate cases for all types for which it is required.

66
go/types/builtins.go
View File

@ -13,9 +13,6 @@ import (
"code.google.com/p/go.tools/go/exact"
)
// TODO(gri): Several built-ins are missing assignment checks. As a result,
// non-constant shift arguments may not be properly type-checked.
// builtin typechecks a call to a built-in and returns the result via x.
// If the call has type errors, the returned x is marked as invalid.
//
@ -35,7 +32,7 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, id builtinId) {
msg = "too many"
}
if msg != "" {
check.invalidOp(call.Pos(), msg+" arguments for %s (expected %d, found %d)", call, bin.nargs, n)
check.invalidOp(call.Pos(), "%s arguments for %s (expected %d, found %d)", msg, call, bin.nargs, n)
goto Error
}
@ -57,20 +54,55 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, id builtinId) {
switch id {
case _Append:
if _, ok := x.typ.Underlying().(*Slice); !ok {
check.invalidArg(x.pos(), "%s is not a typed slice", x)
// 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, _ := S.Underlying().(*Slice); s != nil {
T = s.elt
} else {
check.invalidArg(x.pos(), "%s is not a slice", x)
goto Error
}
resultTyp := x.typ
for _, arg := range args[1:] {
check.expr(x, arg)
// 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 n == 2 && call.Ellipsis.IsValid() && x.isAssignableTo(check.conf, NewSlice(Typ[Byte])) {
check.expr(x, args[1])
if x.mode == invalid {
goto Error
}
// TODO(gri) check assignability
if isString(x.typ) {
x.mode = value
x.typ = S
x.expr = call
return
}
alist = append(alist, *x)
// fallthrough
}
// check general case by creating custom signature
sig := makeSig(S, S, NewSlice(T)) // []T required for variadic signature
sig.isVariadic = true
check.arguments(x, call, sig, func(x *operand, i int) {
// only evaluate arguments that have not been evaluated before
if i < len(alist) {
*x = alist[i]
return
}
check.expr(x, args[i])
})
x.mode = value
x.typ = resultTyp
x.typ = S
case _Cap, _Len:
mode := invalid
@ -416,6 +448,18 @@ Error:
x.expr = call
}
// makeSig returns the signature for the given parameter and result types.
func makeSig(result Type, params ...Type) *Signature {
list := make([]*Var, len(params))
for i, param := range params {
list[i] = NewVar(token.NoPos, nil, "", param)
}
return &Signature{
params: NewTuple(list...),
results: NewTuple(NewVar(token.NoPos, nil, "", result)),
}
}
// implicitArrayDeref returns A if typ is of the form *A and A is an array;
// otherwise it returns typ.
//

114
go/types/call.go
View File

@ -62,60 +62,7 @@ func (check *checker) call(x *operand, e *ast.CallExpr) exprKind {
return statement
}
passSlice := false
if e.Ellipsis.IsValid() {
// last argument is of the form x...
if sig.isVariadic {
passSlice = true
} else {
check.errorf(e.Ellipsis, "cannot use ... in call to non-variadic %s", e.Fun)
// ok to continue
}
}
// evaluate arguments
n := len(e.Args) // argument count
if n == 1 {
// single argument but possibly a multi-valued function call
arg := e.Args[0]
check.expr(x, arg)
if x.mode != invalid {
if t, ok := x.typ.(*Tuple); ok {
// argument is multi-valued function call
n = t.Len()
for i := 0; i < n; i++ {
x.mode = value
x.expr = arg
x.typ = t.At(i).typ
check.argument(sig, i, x, passSlice && i == n-1)
}
} else {
// single value
check.argument(sig, 0, x, passSlice)
}
} else {
n = sig.params.Len() // avoid additional argument length errors below
}
} else {
// zero or multiple arguments
for i, arg := range e.Args {
check.expr(x, arg)
if x.mode != invalid {
check.argument(sig, i, x, passSlice && i == n-1)
}
}
}
// check argument count
if sig.isVariadic {
// a variadic function accepts an "empty"
// last argument: count one extra
n++
}
if n < sig.params.Len() {
check.errorf(e.Rparen, "too few arguments in call to %s", e.Fun)
// ok to continue
}
check.arguments(x, e, sig, func(x *operand, i int) { check.expr(x, e.Args[i]) })
// determine result
switch sig.results.Len() {
@ -134,6 +81,65 @@ func (check *checker) call(x *operand, e *ast.CallExpr) exprKind {
}
}
// arguments checks argument passing for the call with the given signature.
// The arg function provides the operand for the i'th argument.
func (check *checker) arguments(x *operand, call *ast.CallExpr, sig *Signature, arg func(*operand, int)) {
passSlice := false
if call.Ellipsis.IsValid() {
// last argument is of the form x...
if sig.isVariadic {
passSlice = true
} else {
check.errorf(call.Ellipsis, "cannot use ... in call to non-variadic %s", call.Fun)
// ok to continue
}
}
// evaluate arguments
n := len(call.Args) // argument count
if n == 1 {
// single argument but possibly a multi-valued function call
arg(x, 0)
if x.mode != invalid {
if t, ok := x.typ.(*Tuple); ok {
// argument is multi-valued function call
n = t.Len()
expr := call.Args[0]
for i := 0; i < n; i++ {
x.mode = value
x.expr = expr
x.typ = t.At(i).typ
check.argument(sig, i, x, passSlice && i == n-1)
}
} else {
// single value
check.argument(sig, 0, x, passSlice)
}
} else {
n = sig.params.Len() // avoid additional argument length errors below
}
} else {
// zero or multiple arguments
for i := range call.Args {
arg(x, i)
if x.mode != invalid {
check.argument(sig, i, x, passSlice && i == n-1)
}
}
}
// check argument count
if sig.isVariadic {
// a variadic function accepts an "empty"
// last argument: count one extra
n++
}
if n < sig.params.Len() {
check.errorf(call.Rparen, "too few arguments in call to %s", call.Fun)
// ok to continue
}
}
// argument checks passing of argument x to the i'th parameter of the given signature.
// If passSlice is set, the argument is followed by ... in the call.
func (check *checker) argument(sig *Signature, i int, x *operand, passSlice bool) {

52
go/types/testdata/builtins.src vendored
View File

@ -8,15 +8,59 @@ package builtins
import "unsafe"
func _append() {
func _append1() {
var b byte
var x int
var s []byte
_ = append /* ERROR "argument" */ ()
_ = append("foo" /* ERROR "not a typed slice" */)
_ = append(nil /* ERROR "not a typed slice" */, s)
_ = append(x /* ERROR "not a typed slice" */, s)
_ = append("foo" /* ERROR "not a slice" */ )
_ = append(nil /* ERROR "not a slice" */ , s)
_ = append(x /* ERROR "not a slice" */ , s)
_ = append(s)
append /* ERROR "not used" */ (s)
_ = append(s, b)
_ = append(s, x /* ERROR cannot pass argument x */ )
_ = append(s, s /* ERROR cannot pass argument s */ )
_ = append(s /* ERROR can only use ... with matching parameter */ ...)
_ = append(s, b, s /* ERROR can only use ... with matching parameter */ ...)
_ = append(s, 1, 2, 3)
_ = append(s, 1, 2, 3, x /* ERROR cannot pass argument x */ , 5, 6, 6)
_ = append(s, 1, 2, s /* ERROR can only use ... with matching parameter */ ...)
_ = append([]interface{}(nil), 1, 2, "foo", x, 3.1425, false)
type S []byte
type T string
var t T
_ = append(s, "foo" /* ERROR cannot convert */ )
_ = append(s, "foo"...)
_ = append(S(s), "foo" /* ERROR cannot convert */ )
_ = append(S(s), "foo"...)
_ = append(s, t /* ERROR cannot pass argument t */ )
_ = append(s, t...)
_ = append(s, T("foo")...)
_ = append(S(s), t /* ERROR cannot pass argument t */ )
_ = append(S(s), t...)
_ = append(S(s), T("foo")...)
_ = append([]string{}, t /* ERROR cannot pass argument t */ , "foo")
_ = append([]T{}, t, "foo")
}
// from the spec
func _append2() {
s0 := []int{0, 0}
s1 := append(s0, 2) // append a single element s1 == []int{0, 0, 2}
s2 := append(s1, 3, 5, 7) // append multiple elements s2 == []int{0, 0, 2, 3, 5, 7}
s3 := append(s2, s0...) // append a slice s3 == []int{0, 0, 2, 3, 5, 7, 0, 0}
s4 := append(s3[3:6], s3[2:]...) // append overlapping slice s4 == []int{3, 5, 7, 2, 3, 5, 7, 0, 0}
var t []interface{}
t = append(t, 42, 3.1415, "foo") // t == []interface{}{42, 3.1415, "foo"}
var b []byte
b = append(b, "bar"...) // append string contents b == []byte{'b', 'a', 'r' }
_ = s4
}
func _cap() {