[dev.typeparams] cmd/compile/internal/types2: fix a panic in missingMethod

When static == false, missingMethod incorrectly continues with a nil
Func.

Also remove some unnecessary type names from typeterm_test.go, which was
done in the go/types port.

Change-Id: I21fa637ac82b115563d3601314a470a5a43f9ae0
Reviewed-on: https://go-review.googlesource.com/c/go/+/339672
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/types2/lookup.go

@@ -308,7 +308,10 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method,
 		for _, m := range T.typeSet().methods {
 			_, f := ityp.typeSet().LookupMethod(m.pkg, m.name)
 
-			if f == nil && static {
+			if f == nil {
+				if !static {
+					continue
+				}
 				return m, f
 			}
 

src/cmd/compile/internal/types2/typeterm_test.go

@@ -11,11 +11,11 @@ import (
 
 var testTerms = map[string]*term{
 	"∅":       nil,
-	"⊤":       &term{},
-	"int":     &term{false, Typ[Int]},
-	"~int":    &term{true, Typ[Int]},
-	"string":  &term{false, Typ[String]},
-	"~string": &term{true, Typ[String]},
+	"⊤":       {},
+	"int":     {false, Typ[Int]},
+	"~int":    {true, Typ[Int]},
+	"string":  {false, Typ[String]},
+	"~string": {true, Typ[String]},
 	// TODO(gri) add a defined type
 }