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[dev.typeparams] cmd/compile/internal/types2: remove code for implicit type arguments

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The design draft doesn't support this anymore.

Also: Fixed a potential bug in the receiver unpack code
      (found by rfindley@).

Change-Id: Ic52eedc686adcb4d5a98884ad0134679c3685c13
Reviewed-on: https://go-review.googlesource.com/c/go/+/278853
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 2020-12-16 17:16:23 -08:00
parent 068dd0470b
commit c4f0da5750
2 changed files with 4 additions and 39 deletions
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41
src/cmd/compile/internal/types2/decl.go
View File

@ -686,33 +686,24 @@ func (check *Checker) collectTypeParams(list []*syntax.Field) (tparams []*TypeNa
var bound Type
for i, j := 0, 0; i < len(list); i = j {
f := list[i]
ftype := f.Type
// determine the range of type parameters list[i:j] with identical type bound
// (declared as in (type a, b, c B))
j = i + 1
for j < len(list) && list[j].Type == ftype {
for j < len(list) && list[j].Type == f.Type {
j++
}
// this should never be the case, but be careful
if ftype == nil {
if f.Type == nil {
continue
}
// If the type bound expects exactly one type argument, permit leaving
// it away and use the corresponding type parameter as implicit argument.
// This allows us to write (type p b(p), q b(q), r b(r)) as (type p, q, r b).
// Enabled if enableImplicitTParam is set.
const enableImplicitTParam = false
// The predeclared identifier "any" is visible only as a constraint
// in a type parameter list. Look for it before general constraint
// resolution.
if tident, _ := f.Type.(*syntax.Name); tident != nil && tident.Value == "any" && check.lookup("any") == nil {
bound = universeAny
} else if enableImplicitTParam {
bound = check.anyType(f.Type)
} else {
bound = check.typ(f.Type)
}
@ -723,34 +714,6 @@ func (check *Checker) collectTypeParams(list []*syntax.Field) (tparams []*TypeNa
// type C(type T C) interface {}
// (issue #39724).
if _, ok := bound.Under().(*Interface); ok {
if enableImplicitTParam && isGeneric(bound) {
base := bound.(*Named) // only a *Named type can be generic
if j-i != 1 || len(base.tparams) != 1 {
// TODO(gri) make this error message better
check.errorf(ftype, "cannot use generic type %s without instantiation (more than one type parameter)", bound)
bound = Typ[Invalid]
continue
}
// We have exactly one type parameter.
// "Manually" instantiate the bound with each type
// parameter the bound applies to.
// TODO(gri) this code (in more general form) is also in
// checker.typInternal for the *ast.CallExpr case. Factor?
typ := new(instance)
typ.check = check
typ.pos = ftype.Pos()
typ.base = base
typ.targs = []Type{tparams[i].typ}
typ.poslist = []syntax.Pos{f.Name.Pos()}
// Make sure we check instantiation works at least once
// and that the resulting type is valid.
check.atEnd(func() {
check.validType(typ.expand(), nil)
})
// update bound and recorded type
bound = typ
check.recordTypeAndValue(ftype, typexpr, typ, nil)
}
// set the type bounds
for i < j {
tparams[i].typ.(*TypeParam).bound = bound

2
src/cmd/compile/internal/types2/resolver.go
View File

@ -495,11 +495,13 @@ L: // unpack receiver type
case *syntax.ParenExpr:
rtyp = t.X
// case *ast.StarExpr:
// ptr = true
// rtyp = t.X
case *syntax.Operation:
if t.Op != syntax.Mul || t.Y != nil {
break
}
ptr = true
rtyp = t.X
default:
break L