[dev.typeparams] Fix problem with 14.go

Removed a case in transformCall() where we were setting a type on n,
which isn't needed, since noder2 already set the type of n. More
importantly, we are losing information, since the type of the results
may be a shape type, but the actual type of call is the known type
from types2, which may be a concrete type (in this case Zero[MyInt]).
That concrete type will then be used correctly if the concrete result is
converted to an interface.

If we are inlining the call to Zero[MyInt], we need to add an implicit
CONVNOP operation, since we are going to use the result variable
directly, which has a shape type. So, add an implicit CONVNOP to
remember that the known type is the concrete type.

Also cleaned up 14.go a bit, so it is more understandable. Renamed type
T to AnyInt, since T is used elsewhere as a type parameter. Reformatted
Zero function and added a comment.

Change-Id: Id917a2e054e0bbae9bd302232853fa8741d49b64
Reviewed-on: https://go-review.googlesource.com/c/go/+/336430
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/test/typeparam/mdempsky/14.go b/test/typeparam/mdempsky/14.go
index 61f9436910..ba685bc35c 100644
--- a/test/typeparam/mdempsky/14.go
+++ b/test/typeparam/mdempsky/14.go
@@ -6,11 +6,14 @@
 
 package main
 
-func Zero[T any]() (_ T) { return }
+// Zero returns the zero value of T
+func Zero[T any]() (_ T) {
+	return
+}
 
-type T[X any] int
+type AnyInt[X any] int
 
-func (T[X]) M() {
+func (AnyInt[X]) M() {
 	var have interface{} = Zero[X]()
 	var want interface{} = Zero[MyInt]()
 
@@ -22,7 +25,7 @@ func (T[X]) M() {
 type I interface{ M() }
 
 type MyInt int
-type U = T[MyInt]
+type U = AnyInt[MyInt]
 
 var x = U(0)
 var i I = x