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cmd/compile/internal/types2: factor out index/slice expr handling

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First step towards lightening the load of Checker.exprInternal by
factoring out the code for index and slice expressions; incl. moving
a couple of related methods (Checker.index, Checker.indexedElts).

The code for handling index/slice expressions is copied 1:1 but
occurrences of "goto Error" are replaced by "x.mode = invalid"
followed by a "return".

Change-Id: I44048dcc4851dc5e24f5f169c17f536a37a6a676
Reviewed-on: https://go-review.googlesource.com/c/go/+/308370
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2021-04-07 17:47:14 -07:00
parent 4638545d85
commit 36c5f902f9
2 changed files with 407 additions and 374 deletions
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376
src/cmd/compile/internal/types2/expr.go
View File

@ -1043,104 +1043,6 @@ func (check *Checker) binary(x *operand, e syntax.Expr, lhs, rhs syntax.Expr, op
// x.typ is unchanged
}
// index checks an index expression for validity.
// If max >= 0, it is the upper bound for index.
// If the result typ is != Typ[Invalid], index is valid and typ is its (possibly named) integer type.
// If the result val >= 0, index is valid and val is its constant int value.
func (check *Checker) index(index syntax.Expr, max int64) (typ Type, val int64) {
typ = Typ[Invalid]
val = -1
var x operand
check.expr(&x, index)
if x.mode == invalid {
return
}
// an untyped constant must be representable as Int
check.convertUntyped(&x, Typ[Int])
if x.mode == invalid {
return
}
// the index must be of integer type
if !isInteger(x.typ) {
check.errorf(&x, invalidArg+"index %s must be integer", &x)
return
}
if x.mode != constant_ {
return x.typ, -1
}
// a constant index i must be in bounds
if constant.Sign(x.val) < 0 {
check.errorf(&x, invalidArg+"index %s must not be negative", &x)
return
}
v, valid := constant.Int64Val(constant.ToInt(x.val))
if !valid || max >= 0 && v >= max {
if check.conf.CompilerErrorMessages {
check.errorf(&x, "array index %s out of bounds [0:%d]", x.val.String(), max)
} else {
check.errorf(&x, "index %s is out of bounds", &x)
}
return
}
// 0 <= v [ && v < max ]
return Typ[Int], v
}
// indexElts checks the elements (elts) of an array or slice composite literal
// against the literal's element type (typ), and the element indices against
// the literal length if known (length >= 0). It returns the length of the
// literal (maximum index value + 1).
//
func (check *Checker) indexedElts(elts []syntax.Expr, typ Type, length int64) int64 {
visited := make(map[int64]bool, len(elts))
var index, max int64
for _, e := range elts {
// determine and check index
validIndex := false
eval := e
if kv, _ := e.(*syntax.KeyValueExpr); kv != nil {
if typ, i := check.index(kv.Key, length); typ != Typ[Invalid] {
if i >= 0 {
index = i
validIndex = true
} else {
check.errorf(e, "index %s must be integer constant", kv.Key)
}
}
eval = kv.Value
} else if length >= 0 && index >= length {
check.errorf(e, "index %d is out of bounds (>= %d)", index, length)
} else {
validIndex = true
}
// if we have a valid index, check for duplicate entries
if validIndex {
if visited[index] {
check.errorf(e, "duplicate index %d in array or slice literal", index)
}
visited[index] = true
}
index++
if index > max {
max = index
}
// check element against composite literal element type
var x operand
check.exprWithHint(&x, eval, typ)
check.assignment(&x, typ, "array or slice literal")
}
return max
}
// exprKind describes the kind of an expression; the kind
// determines if an expression is valid in 'statement context'.
type exprKind int
@ -1485,291 +1387,17 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
check.selector(x, e)
case *syntax.IndexExpr:
check.exprOrType(x, e.X)
check.indexExpr(x, e)
if x.mode == invalid {
check.use(e.Index)
goto Error
}
if x.mode == typexpr {
// type instantiation
x.mode = invalid
x.typ = check.varType(e)
if x.typ != Typ[Invalid] {
x.mode = typexpr
}
return expression
}
if x.mode == value {
if sig := asSignature(x.typ); sig != nil && len(sig.tparams) > 0 {
// function instantiation
check.funcInst(x, e)
return expression
}
}
// ordinary index expression
valid := false
length := int64(-1) // valid if >= 0
switch typ := optype(x.typ).(type) {
case *Basic:
if isString(typ) {
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// an indexed string always yields a byte value
// (not a constant) even if the string and the
// index are constant
x.mode = value
x.typ = universeByte // use 'byte' name
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
x.mode = value
}
x.typ = typ.elem
case *Pointer:
if typ := asArray(typ.base); typ != nil {
valid = true
length = typ.len
x.mode = variable
x.typ = typ.elem
}
case *Slice:
valid = true
x.mode = variable
x.typ = typ.elem
case *Map:
var key operand
check.expr(&key, e.Index)
check.assignment(&key, typ.key, "map index")
// ok to continue even if indexing failed - map element type is known
x.mode = mapindex
x.typ = typ.elem
x.expr = e
return expression
case *Sum:
// A sum type can be indexed if all of the sum's types
// support indexing and have the same index and element
// type. Special rules apply for maps in the sum type.
var tkey, telem Type // key is for map types only
nmaps := 0 // number of map types in sum type
if typ.is(func(t Type) bool {
var e Type
switch t := under(t).(type) {
case *Basic:
if isString(t) {
e = universeByte
}
case *Array:
e = t.elem
case *Pointer:
if t := asArray(t.base); t != nil {
e = t.elem
}
case *Slice:
e = t.elem
case *Map:
// If there are multiple maps in the sum type,
// they must have identical key types.
// TODO(gri) We may be able to relax this rule
// but it becomes complicated very quickly.
if tkey != nil && !Identical(t.key, tkey) {
return false
}
tkey = t.key
e = t.elem
nmaps++
case *TypeParam:
check.errorf(x, "type of %s contains a type parameter - cannot index (implementation restriction)", x)
case *instance:
panic("unimplemented")
}
if e == nil || telem != nil && !Identical(e, telem) {
return false
}
telem = e
return true
}) {
// If there are maps, the index expression must be assignable
// to the map key type (as for simple map index expressions).
if nmaps > 0 {
var key operand
check.expr(&key, e.Index)
check.assignment(&key, tkey, "map index")
// ok to continue even if indexing failed - map element type is known
// If there are only maps, we are done.
if nmaps == len(typ.types) {
x.mode = mapindex
x.typ = telem
x.expr = e
return expression
}
// Otherwise we have mix of maps and other types. For
// now we require that the map key be an integer type.
// TODO(gri) This is probably not good enough.
valid = isInteger(tkey)
// avoid 2nd indexing error if indexing failed above
if !valid && key.mode == invalid {
goto Error
}
x.mode = value // map index expressions are not addressable
} else {
// no maps
valid = true
x.mode = variable
}
x.typ = telem
}
}
if !valid {
check.errorf(x, invalidOp+"cannot index %s", x)
goto Error
}
if e.Index == nil {
check.errorf(e, invalidAST+"missing index for %s", x)
goto Error
}
index := e.Index
if l, _ := index.(*syntax.ListExpr); l != nil {
if n := len(l.ElemList); n <= 1 {
check.errorf(e, invalidAST+"invalid use of ListExpr for index expression %v with %d indices", e, n)
goto Error
}
// len(l.ElemList) > 1
check.error(l.ElemList[1], invalidOp+"more than one index")
index = l.ElemList[0] // continue with first index
}
// In pathological (invalid) cases (e.g.: type T1 [][[]T1{}[0][0]]T0)
// the element type may be accessed before it's set. Make sure we have
// a valid type.
if x.typ == nil {
x.typ = Typ[Invalid]
}
check.index(index, length)
// ok to continue
case *syntax.SliceExpr:
check.expr(x, e.X)
check.sliceExpr(x, e)
if x.mode == invalid {
check.use(e.Index[:]...)
goto Error
}
valid := false
length := int64(-1) // valid if >= 0
switch typ := optype(x.typ).(type) {
case *Basic:
if isString(typ) {
if e.Full {
check.error(x, invalidOp+"3-index slice of string")
goto Error
}
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// spec: "For untyped string operands the result
// is a non-constant value of type string."
if typ.kind == UntypedString {
x.typ = Typ[String]
}
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
check.errorf(x, invalidOp+"%s (slice of unaddressable value)", x)
goto Error
}
x.typ = &Slice{elem: typ.elem}
case *Pointer:
if typ := asArray(typ.base); typ != nil {
valid = true
length = typ.len
x.typ = &Slice{elem: typ.elem}
}
case *Slice:
valid = true
// x.typ doesn't change
case *Sum, *TypeParam:
check.error(x, "generic slice expressions not yet implemented")
goto Error
}
if !valid {
check.errorf(x, invalidOp+"cannot slice %s", x)
goto Error
}
x.mode = value
// spec: "Only the first index may be omitted; it defaults to 0."
if e.Full && (e.Index[1] == nil || e.Index[2] == nil) {
check.error(e, invalidAST+"2nd and 3rd index required in 3-index slice")
goto Error
}
// check indices
var ind [3]int64
for i, expr := range e.Index {
x := int64(-1)
switch {
case expr != nil:
// The "capacity" is only known statically for strings, arrays,
// and pointers to arrays, and it is the same as the length for
// those types.
max := int64(-1)
if length >= 0 {
max = length + 1
}
if _, v := check.index(expr, max); v >= 0 {
x = v
}
case i == 0:
// default is 0 for the first index
x = 0
case length >= 0:
// default is length (== capacity) otherwise
x = length
}
ind[i] = x
}
// constant indices must be in range
// (check.index already checks that existing indices >= 0)
L:
for i, x := range ind[:len(ind)-1] {
if x > 0 {
for _, y := range ind[i+1:] {
if y >= 0 && x > y {
check.errorf(e, "invalid slice indices: %d > %d", x, y)
break L // only report one error, ok to continue
}
}
}
}
case *syntax.AssertExpr:
check.expr(x, e.X)
if x.mode == invalid {

405
src/cmd/compile/internal/types2/index.go Normal file
View File

@ -0,0 +1,405 @@
// Copyright 2021 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 index/slice expressions.
package types2
import (
"cmd/compile/internal/syntax"
"go/constant"
)
func (check *Checker) indexExpr(x *operand, e *syntax.IndexExpr) {
check.exprOrType(x, e.X)
if x.mode == invalid {
check.use(e.Index)
return
}
if x.mode == typexpr {
// type instantiation
x.mode = invalid
x.typ = check.varType(e)
if x.typ != Typ[Invalid] {
x.mode = typexpr
}
return
}
if x.mode == value {
if sig := asSignature(x.typ); sig != nil && len(sig.tparams) > 0 {
// function instantiation
check.funcInst(x, e)
return
}
}
// ordinary index expression
valid := false
length := int64(-1) // valid if >= 0
switch typ := optype(x.typ).(type) {
case *Basic:
if isString(typ) {
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// an indexed string always yields a byte value
// (not a constant) even if the string and the
// index are constant
x.mode = value
x.typ = universeByte // use 'byte' name
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
x.mode = value
}
x.typ = typ.elem
case *Pointer:
if typ := asArray(typ.base); typ != nil {
valid = true
length = typ.len
x.mode = variable
x.typ = typ.elem
}
case *Slice:
valid = true
x.mode = variable
x.typ = typ.elem
case *Map:
var key operand
check.expr(&key, e.Index)
check.assignment(&key, typ.key, "map index")
// ok to continue even if indexing failed - map element type is known
x.mode = mapindex
x.typ = typ.elem
x.expr = e
return
case *Sum:
// A sum type can be indexed if all of the sum's types
// support indexing and have the same index and element
// type. Special rules apply for maps in the sum type.
var tkey, telem Type // key is for map types only
nmaps := 0 // number of map types in sum type
if typ.is(func(t Type) bool {
var e Type
switch t := under(t).(type) {
case *Basic:
if isString(t) {
e = universeByte
}
case *Array:
e = t.elem
case *Pointer:
if t := asArray(t.base); t != nil {
e = t.elem
}
case *Slice:
e = t.elem
case *Map:
// If there are multiple maps in the sum type,
// they must have identical key types.
// TODO(gri) We may be able to relax this rule
// but it becomes complicated very quickly.
if tkey != nil && !Identical(t.key, tkey) {
return false
}
tkey = t.key
e = t.elem
nmaps++
case *TypeParam:
check.errorf(x, "type of %s contains a type parameter - cannot index (implementation restriction)", x)
case *instance:
panic("unimplemented")
}
if e == nil || telem != nil && !Identical(e, telem) {
return false
}
telem = e
return true
}) {
// If there are maps, the index expression must be assignable
// to the map key type (as for simple map index expressions).
if nmaps > 0 {
var key operand
check.expr(&key, e.Index)
check.assignment(&key, tkey, "map index")
// ok to continue even if indexing failed - map element type is known
// If there are only maps, we are done.
if nmaps == len(typ.types) {
x.mode = mapindex
x.typ = telem
x.expr = e
return
}
// Otherwise we have mix of maps and other types. For
// now we require that the map key be an integer type.
// TODO(gri) This is probably not good enough.
valid = isInteger(tkey)
// avoid 2nd indexing error if indexing failed above
if !valid && key.mode == invalid {
x.mode = invalid
return
}
x.mode = value // map index expressions are not addressable
} else {
// no maps
valid = true
x.mode = variable
}
x.typ = telem
}
}
if !valid {
check.errorf(x, invalidOp+"cannot index %s", x)
x.mode = invalid
return
}
if e.Index == nil {
check.errorf(e, invalidAST+"missing index for %s", x)
x.mode = invalid
return
}
index := e.Index
if l, _ := index.(*syntax.ListExpr); l != nil {
if n := len(l.ElemList); n <= 1 {
check.errorf(e, invalidAST+"invalid use of ListExpr for index expression %v with %d indices", e, n)
x.mode = invalid
return
}
// len(l.ElemList) > 1
check.error(l.ElemList[1], invalidOp+"more than one index")
index = l.ElemList[0] // continue with first index
}
// In pathological (invalid) cases (e.g.: type T1 [][[]T1{}[0][0]]T0)
// the element type may be accessed before it's set. Make sure we have
// a valid type.
if x.typ == nil {
x.typ = Typ[Invalid]
}
check.index(index, length)
}
func (check *Checker) sliceExpr(x *operand, e *syntax.SliceExpr) {
check.expr(x, e.X)
if x.mode == invalid {
check.use(e.Index[:]...)
return
}
valid := false
length := int64(-1) // valid if >= 0
switch typ := optype(x.typ).(type) {
case *Basic:
if isString(typ) {
if e.Full {
check.error(x, invalidOp+"3-index slice of string")
x.mode = invalid
return
}
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// spec: "For untyped string operands the result
// is a non-constant value of type string."
if typ.kind == UntypedString {
x.typ = Typ[String]
}
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
check.errorf(x, invalidOp+"%s (slice of unaddressable value)", x)
x.mode = invalid
return
}
x.typ = &Slice{elem: typ.elem}
case *Pointer:
if typ := asArray(typ.base); typ != nil {
valid = true
length = typ.len
x.typ = &Slice{elem: typ.elem}
}
case *Slice:
valid = true
// x.typ doesn't change
case *Sum, *TypeParam:
check.error(x, "generic slice expressions not yet implemented")
x.mode = invalid
return
}
if !valid {
check.errorf(x, invalidOp+"cannot slice %s", x)
x.mode = invalid
return
}
x.mode = value
// spec: "Only the first index may be omitted; it defaults to 0."
if e.Full && (e.Index[1] == nil || e.Index[2] == nil) {
check.error(e, invalidAST+"2nd and 3rd index required in 3-index slice")
x.mode = invalid
return
}
// check indices
var ind [3]int64
for i, expr := range e.Index {
x := int64(-1)
switch {
case expr != nil:
// The "capacity" is only known statically for strings, arrays,
// and pointers to arrays, and it is the same as the length for
// those types.
max := int64(-1)
if length >= 0 {
max = length + 1
}
if _, v := check.index(expr, max); v >= 0 {
x = v
}
case i == 0:
// default is 0 for the first index
x = 0
case length >= 0:
// default is length (== capacity) otherwise
x = length
}
ind[i] = x
}
// constant indices must be in range
// (check.index already checks that existing indices >= 0)
L:
for i, x := range ind[:len(ind)-1] {
if x > 0 {
for _, y := range ind[i+1:] {
if y >= 0 && x > y {
check.errorf(e, "invalid slice indices: %d > %d", x, y)
break L // only report one error, ok to continue
}
}
}
}
}
// index checks an index expression for validity.
// If max >= 0, it is the upper bound for index.
// If the result typ is != Typ[Invalid], index is valid and typ is its (possibly named) integer type.
// If the result val >= 0, index is valid and val is its constant int value.
func (check *Checker) index(index syntax.Expr, max int64) (typ Type, val int64) {
typ = Typ[Invalid]
val = -1
var x operand
check.expr(&x, index)
if x.mode == invalid {
return
}
// an untyped constant must be representable as Int
check.convertUntyped(&x, Typ[Int])
if x.mode == invalid {
return
}
// the index must be of integer type
if !isInteger(x.typ) {
check.errorf(&x, invalidArg+"index %s must be integer", &x)
return
}
if x.mode != constant_ {
return x.typ, -1
}
// a constant index i must be in bounds
if constant.Sign(x.val) < 0 {
check.errorf(&x, invalidArg+"index %s must not be negative", &x)
return
}
v, valid := constant.Int64Val(constant.ToInt(x.val))
if !valid || max >= 0 && v >= max {
if check.conf.CompilerErrorMessages {
check.errorf(&x, "array index %s out of bounds [0:%d]", x.val.String(), max)
} else {
check.errorf(&x, "index %s is out of bounds", &x)
}
return
}
// 0 <= v [ && v < max ]
return Typ[Int], v
}
// indexElts checks the elements (elts) of an array or slice composite literal
// against the literal's element type (typ), and the element indices against
// the literal length if known (length >= 0). It returns the length of the
// literal (maximum index value + 1).
func (check *Checker) indexedElts(elts []syntax.Expr, typ Type, length int64) int64 {
visited := make(map[int64]bool, len(elts))
var index, max int64
for _, e := range elts {
// determine and check index
validIndex := false
eval := e
if kv, _ := e.(*syntax.KeyValueExpr); kv != nil {
if typ, i := check.index(kv.Key, length); typ != Typ[Invalid] {
if i >= 0 {
index = i
validIndex = true
} else {
check.errorf(e, "index %s must be integer constant", kv.Key)
}
}
eval = kv.Value
} else if length >= 0 && index >= length {
check.errorf(e, "index %d is out of bounds (>= %d)", index, length)
} else {
validIndex = true
}
// if we have a valid index, check for duplicate entries
if validIndex {
if visited[index] {
check.errorf(e, "duplicate index %d in array or slice literal", index)
}
visited[index] = true
}
index++
if index > max {
max = index
}
// check element against composite literal element type
var x operand
check.exprWithHint(&x, eval, typ)
check.assignment(&x, typ, "array or slice literal")
}
return max
}