Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/compile: deal with helper generic types that add methods to T

Browse source 
Deal with cases like: 'type P[T any] T' (used to add methods to an
arbitrary type T), In this case, P[T] has kind types.TTYPEPARAM (as does
T itself), but requires more code to substitute than a simple TTYPEPARAM
T. See the comment near the beginning of subster.typ() in stencil.go.

Add new test absdiff.go. This test has a case for complex types (which
I've commented out) that will only work when we deal better with Go
builtins in generic functions (like real and imag).

Remove change in fmt.go for TTYPEPARAMS that is no longer needed (since
all TTYPEPARAMS have a sym) and was sometimes causing an extra prefix
when formatting method names.

Separate out the setting of a TTYPEPARAM bound, since it can reference
the TTYPEPARAM being defined, so must be done separately. Also, we don't
currently (and may not ever) need bounds after types2 typechecking.

Change-Id: Id173057e0c4563b309b95e665e9c1151ead4ba77
Reviewed-on: https://go-review.googlesource.com/c/go/+/300049
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Dan Scales 2021-03-05 22:07:56 -08:00
parent 5edab39f49
commit 1811aeae66
5 changed files with 138 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

29
src/cmd/compile/internal/noder/stencil.go
View file

@ -553,7 +553,25 @@ func (subst *subster) typ(t *types.Type) *types.Type {
return subst.targs[i].Type()
}
}
return t
// If t is a simple typeparam T, then t has the name/symbol 'T'
// and t.Underlying() == t.
//
// However, consider the type definition: 'type P[T any] T'. We
// might use this definition so we can have a variant of type T
// that we can add new methods to. Suppose t is a reference to
// P[T]. t has the name 'P[T]', but its kind is TTYPEPARAM,
// because P[T] is defined as T. If we look at t.Underlying(), it
// is different, because the name of t.Underlying() is 'T' rather
// than 'P[T]'. But the kind of t.Underlying() is also TTYPEPARAM.
// In this case, we do the needed recursive substitution in the
// case statement below.
if t.Underlying() == t {
// t is a simple typeparam that didn't match anything in tparam
return t
}
// t is a more complex typeparam (e.g. P[T], as above, whose
// definition is just T).
assert(t.Sym() != nil)
}
var newsym *types.Sym
@ -591,6 +609,15 @@ func (subst *subster) typ(t *types.Type) *types.Type {
var newt *types.Type
switch t.Kind() {
case types.TTYPEPARAM:
if t.Sym() == newsym {
// The substitution did not change the type.
return t
}
// Substitute the underlying typeparam (e.g. T in P[T], see
// the example describing type P[T] above).
newt = subst.typ(t.Underlying())
assert(newt != t)
case types.TARRAY:
elem := t.Elem()