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cmd/compile/internal/types2: remove tparamIsIface flag and corresponding dead code

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Added/clarified some comments.

Change-Id: Ib08d3343ff08c23cc8880a27a0148d1ff077a80f
Reviewed-on: https://go-review.googlesource.com/c/go/+/363654
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 2021-11-12 08:59:49 -08:00
parent bc0b98eeff
commit 787708a6ff
9 changed files with 24 additions and 162 deletions
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27
src/cmd/compile/internal/types2/builtins.go
View File

@ -179,28 +179,10 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
}
case *Interface:
if tparamIsIface && isTypeParam(x.typ) {
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 !isTypeParam(x.typ) {
break
}
case *TypeParam:
assert(!tparamIsIface)
if t.underIs(func(t Type) bool {
if t.typeSet().underIs(func(t Type) bool {
switch t := arrayPtrDeref(t).(type) {
case *Basic:
if isString(t) && id == _Len {
@ -820,9 +802,6 @@ func hasVarSize(t Type) bool {
}
case *Interface:
return isTypeParam(t)
case *TypeParam:
assert(!tparamIsIface)
return true
case *Named, *Union:
unreachable()
}

4
src/cmd/compile/internal/types2/decl.go
View File

@ -673,6 +673,10 @@ func (check *Checker) collectTypeParams(dst **TypeParamList, list []*syntax.Fiel
check.later(func() {
for i, bound := range bounds {
if isTypeParam(bound) {
// We may be able to allow this since it is now well-defined what
// the underlying type and thus type set of a type parameter is.
// But we may need some additional form of cycle detection within
// type parameter lists.
check.error(posers[i], "cannot use a type parameter as constraint")
}
}

15
src/cmd/compile/internal/types2/expr.go
View File

@ -659,7 +659,7 @@ func (check *Checker) convertUntyped(x *operand, target Type) {
newType, val, code := check.implicitTypeAndValue(x, target)
if code != 0 {
t := target
if !tparamIsIface || !isTypeParam(target) {
if !isTypeParam(target) {
t = safeUnderlying(target)
}
check.invalidConversion(code, x, t)
@ -741,19 +741,8 @@ func (check *Checker) implicitTypeAndValue(x *operand, target Type) (Type, const
default:
return nil, nil, _InvalidUntypedConversion
}
case *TypeParam:
assert(!tparamIsIface)
if !u.underIs(func(u Type) bool {
if u == nil {
return false
}
t, _, _ := check.implicitTypeAndValue(x, u)
return t != nil
}) {
return nil, nil, _InvalidUntypedConversion
}
case *Interface:
if tparamIsIface && isTypeParam(target) {
if isTypeParam(target) {
if !u.typeSet().underIs(func(u Type) bool {
if u == nil {
return false

89
src/cmd/compile/internal/types2/index.go
View File

@ -100,97 +100,14 @@ func (check *Checker) indexExpr(x *operand, e *syntax.IndexExpr) (isFuncInst boo
return false
case *Interface:
// Note: The body of this 'if' statement is the same as the body
// of the case for type parameters below. If we keep both
// these branches we should factor out the code.
if tparamIsIface && isTypeParam(x.typ) {
// TODO(gri) report detailed failure cause for better error messages
var key, elem Type // key != nil: we must have all maps
mode := variable // non-maps result mode
// TODO(gri) factor out closure and use it for non-typeparam cases as well
if typ.typeSet().underIs(func(u Type) bool {
l := int64(-1) // valid if >= 0
var k, e Type // k is only set for maps
switch t := u.(type) {
case *Basic:
if isString(t) {
e = universeByte
mode = value
}
case *Array:
l = t.len
e = t.elem
if x.mode != variable {
mode = value
}
case *Pointer:
if t, _ := under(t.base).(*Array); t != nil {
l = t.len
e = t.elem
}
case *Slice:
e = t.elem
case *Map:
k = t.key
e = t.elem
}
if e == nil {
return false
}
if elem == nil {
// first type
length = l
key, elem = k, e
return true
}
// all map keys must be identical (incl. all nil)
// (that is, we cannot mix maps with other types)
if !Identical(key, k) {
return false
}
// all element types must be identical
if !Identical(elem, e) {
return false
}
// track the minimal length for arrays, if any
if l >= 0 && l < length {
length = l
}
return true
}) {
// For maps, the index expression must be assignable to the map key type.
if key != nil {
index := check.singleIndex(e)
if index == nil {
x.mode = invalid
return false
}
var k operand
check.expr(&k, index)
check.assignment(&k, key, "map index")
// ok to continue even if indexing failed - map element type is known
x.mode = mapindex
x.typ = elem
x.expr = e
return false
}
// no maps
valid = true
x.mode = mode
x.typ = elem
}
if !isTypeParam(x.typ) {
break
}
case *TypeParam:
// Note: The body of this case is the same as the body of the 'if'
// statement in the interface case above. If we keep both
// these branches we should factor out the code.
// TODO(gri) report detailed failure cause for better error messages
assert(!tparamIsIface)
var key, elem Type // key != nil: we must have all maps
mode := variable // non-maps result mode
// TODO(gri) factor out closure and use it for non-typeparam cases as well
if typ.underIs(func(u Type) bool {
if typ.typeSet().underIs(func(u Type) bool {
l := int64(-1) // valid if >= 0
var k, e Type // k is only set for maps
switch t := u.(type) {

18
src/cmd/compile/internal/types2/predicates.go
View File

@ -131,13 +131,7 @@ func comparable(T Type, seen map[Type]bool) bool {
case *Array:
return comparable(t.elem, seen)
case *Interface:
if tparamIsIface && isTypeParam(T) {
return t.IsComparable()
}
return true
case *TypeParam:
assert(!tparamIsIface)
return t.iface().IsComparable()
return !isTypeParam(T) || t.IsComparable()
}
return false
}
@ -150,15 +144,7 @@ func hasNil(t Type) bool {
case *Slice, *Pointer, *Signature, *Map, *Chan:
return true
case *Interface:
if tparamIsIface && isTypeParam(t) {
return u.typeSet().underIs(func(u Type) bool {
return u != nil && hasNil(u)
})
}
return true
case *TypeParam:
assert(!tparamIsIface)
return u.underIs(func(u Type) bool {
return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool {
return u != nil && hasNil(u)
})
}

7
src/cmd/compile/internal/types2/sizes.go
View File

@ -67,7 +67,9 @@ func (s *StdSizes) Alignof(T Type) int64 {
case *Slice, *Interface:
// Multiword data structures are effectively structs
// in which each element has size WordSize.
assert(!tparamIsIface || !isTypeParam(T))
// Type parameters lead to variable sizes/alignments;
// StdSizes.Alignof won't be called for them.
assert(!isTypeParam(T))
return s.WordSize
case *Basic:
// Strings are like slices and interfaces.
@ -152,6 +154,9 @@ func (s *StdSizes) Sizeof(T Type) int64 {
offsets := s.Offsetsof(t.fields)
return offsets[n-1] + s.Sizeof(t.fields[n-1].typ)
case *Interface:
// Type parameters lead to variable sizes/alignments;
// StdSizes.Sizeof won't be called for them.
assert(!isTypeParam(T))
return s.WordSize * 2
case *TypeParam, *Union:
unreachable()

5
src/cmd/compile/internal/types2/struct.go
View File

@ -156,11 +156,8 @@ func (check *Checker) structType(styp *Struct, e *syntax.StructType) {
}
case *Pointer:
check.error(embeddedPos, "embedded field type cannot be a pointer")
case *TypeParam:
assert(!tparamIsIface)
check.error(embeddedPos, "embedded field type cannot be a (pointer to a) type parameter")
case *Interface:
if tparamIsIface && isTypeParam(t) {
if isTypeParam(t) {
check.error(embeddedPos, "embedded field type cannot be a (pointer to a) type parameter")
break
}

4
src/cmd/compile/internal/types2/type.go
View File

@ -25,9 +25,7 @@ func under(t Type) Type {
case *Named:
return t.under()
case *TypeParam:
if tparamIsIface {
return t.iface()
}
return t.iface()
}
return t
}

17
src/cmd/compile/internal/types2/typeparam.go
View File

@ -6,12 +6,6 @@ package types2
import "sync/atomic"
// If set, the underlying type of a type parameter is
// is the underlying type of its type constraint, i.e.,
// an interface. With that, a type parameter satisfies
// isInterface.
const tparamIsIface = true
// Note: This is a uint32 rather than a uint64 because the
// respective 64 bit atomic instructions are not available
// on all platforms.
@ -76,10 +70,7 @@ func (t *TypeParam) SetConstraint(bound Type) {
}
func (t *TypeParam) Underlying() Type {
if tparamIsIface {
return t.iface()
}
return t
return t.iface()
}
func (t *TypeParam) String() string { return TypeString(t, nil) }
@ -102,15 +93,11 @@ func (t *TypeParam) iface() *Interface {
return &emptyInterface
}
case *Interface:
if tparamIsIface && isTypeParam(bound) {
if isTypeParam(bound) {
// error is reported in Checker.collectTypeParams
return &emptyInterface
}
ityp = u
case *TypeParam:
assert(!tparamIsIface)
// error is reported in Checker.collectTypeParams
return &emptyInterface
}
// If we don't have an interface, wrap constraint into an implicit interface.