[dev.typeparams] cmd/compile/internal/types2: expand is only required for *Named types

Now that the pointer identity for a *Named type doesn't change
anymore when going from lazy instantiated to actually instantiated
(= expanded) state, expand() only needs to be called when we deal
with *Named types and only if we care about a *Named type's internals.

Remove the expand function and respective calls for all types and
replace with specific t.expand() method calls where t is a *Named.

Change-Id: If82299360d60108b00adc4013b29399aec90b940
Reviewed-on: https://go-review.googlesource.com/c/go/+/340749
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index 7ae2db3412..637829613b 100644
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -114,7 +114,10 @@ func asInterface(t Type) *Interface {
 }
 
 func asNamed(t Type) *Named {
-	e, _ := expand(t).(*Named)
+	e, _ := t.(*Named)
+	if e != nil {
+		e.expand()
+	}
 	return e
 }