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cmd/compile/internal/types2: remove unneccesary tests in implements and lookup

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Because the underlying type of a type parameter is an interface,
the questions whether *P for a type parameter P has methods or
not is settled: P is also an interface pointers to interfaces
don't have methods.

This allows us to eliminate the now unneccesary test in "implements"
and also allows us to remove a special case for type parameters in
"lookupFieldOrMethod".

Change-Id: I8b218f81584a8e42e75884089a44293365b700df
Reviewed-on: https://go-review.googlesource.com/c/go/+/363838
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 2021-11-14 20:45:40 -08:00
parent e08aae2ee4
commit c8d7c5fe05
2 changed files with 1 additions and 11 deletions
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6
src/cmd/compile/internal/types2/instantiate.go
View File

@ -191,12 +191,6 @@ func (check *Checker) implements(V, T Type, qf Qualifier) error {
// V must implement T (methods)
// - check only if we have methods
if Ti.NumMethods() > 0 {
// If the type argument is a pointer to a type parameter, the type argument's
// method set is empty.
// TODO(gri) is this what we want? (spec question)
if base, isPtr := deref(V); isPtr && isTypeParam(base) {
return errorf("%s has no methods", V)
}
if m, wrong := check.missingMethod(V, Ti, true); m != nil {
// TODO(gri) needs to print updated name to avoid major confusion in error message!
// (print warning for now)

6
src/cmd/compile/internal/types2/lookup.go
View File

@ -80,12 +80,8 @@ func lookupFieldOrMethod(T Type, addressable, checkFold bool, pkg *Package, name
typ, isPtr := deref(T)
// *typ where typ is an interface or type parameter has no methods.
// *typ where typ is an interface has no methods.
if isPtr {
// don't look at under(typ) here - was bug (issue #47747)
if _, ok := typ.(*TypeParam); ok {
return
}
if _, ok := under(typ).(*Interface); ok {
return
}