diff options
Diffstat (limited to 'src/cmd/compile/internal/types2/type.go')
| -rw-r--r-- | src/cmd/compile/internal/types2/type.go | 21 |
1 files changed, 7 insertions, 14 deletions
diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go index a943926189..7ae2db3412 100644 --- a/src/cmd/compile/internal/types2/type.go +++ b/src/cmd/compile/internal/types2/type.go @@ -44,28 +44,21 @@ func under(t Type) Type { // optype returns a type's operational type. Except for // type parameters, the operational type is the same // as the underlying type (as returned by under). For -// Type parameters, the operational type is determined -// by the corresponding type bound's type list. The -// result may be the bottom or top type, but it is never -// the incoming type parameter. +// Type parameters, the operational type is the structural +// type, if any; otherwise it's the top type. +// The result is never the incoming type parameter. func optype(typ Type) Type { if t := asTypeParam(typ); t != nil { + // TODO(gri) review accuracy of this comment // If the optype is typ, return the top type as we have // no information. It also prevents infinite recursion // via the asTypeParam converter function. This can happen // for a type parameter list of the form: // (type T interface { type T }). // See also issue #39680. - if a := t.iface().typeSet().types; a != nil { - // If we have a union with a single entry, ignore - // any tilde because under(~t) == under(t). - if u, _ := a.(*Union); u != nil && u.NumTerms() == 1 { - a, _ = u.Term(0) - } - if a != typ { - // a != typ and a is a type parameter => under(a) != typ, so this is ok - return under(a) - } + if u := t.structuralType(); u != nil { + assert(u != typ) // "naked" type parameters cannot be embedded + return u } return theTop } |