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cmd/compile/internal/types2: optimize common case in structuralType

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Most of the time we don't have a type parameter. Avoid using a
closure in that case.

While at it, rename argument from typ to t (to match style in
that file), and clarify the doc string.

Change-Id: Ie62821073f60f353526263f8b380bad9f72d842e
Reviewed-on: https://go-review.googlesource.com/c/go/+/363668
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 2021-11-13 11:02:51 -08:00
parent 184ca3cf99
commit 0a39e4a89d
1 changed files with 13 additions and 8 deletions
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21
src/cmd/compile/internal/types2/type.go
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@ -56,15 +56,20 @@ func match(x, y Type) Type {
return nil
}
// If typ is a type parameter, structuralType returns the single underlying
// type of all types in the corresponding type constraint if it exists, or
// nil otherwise. If the type set contains only unrestricted and restricted
// channel types (with identical element types), the single underlying type
// is the restricted channel type if the restrictions are always the same.
// If typ is not a type parameter, structuralType returns the underlying type.
func structuralType(typ Type) Type {
// If t is not a type parameter, structuralType returns the underlying type.
// If t is a type parameter, structuralType returns the single underlying
// type of all types in its type set if it exists, or nil otherwise. If the
// type set contains only unrestricted and restricted channel types (with
// identical element types), the single underlying type is the restricted
// channel type if the restrictions are always the same, or nil otherwise.
func structuralType(t Type) Type {
tpar, _ := t.(*TypeParam)
if tpar == nil {
return under(t)
}
var su Type
if underIs(typ, func(u Type) bool {
if tpar.underIs(func(u Type) bool {
if u == nil {
return false
}