[dev.typeparams] cmd/compile: small fixes for stenciling

 - Create the stencil name using targ.Type.String(), which handles cases
   where, for example, a type argument is a pointer to a named type,
   etc. *obj.

 - Set name.Def properly for a new stenciled func (have the symbol point
   back to the associated function node).  Will be required when exporting.

 - Add missing copying of Func field when making copies of Name nodes.
   (On purpose (it seems), Name nodes don't have a copy() function, so
   we have to copy all the needed fields explicitly.)

 - Deal with nil type in subster.node(), which is the type of the return
   value for a function that doesn't return anything.

 - Fix min to match standard want/go form, and add in float tests.  Changed
   Got -> got in bunch of other typeparam tests.

 - Add new tests index.go, settable.go, and smallest.go (similar to
   examples in the type param proposal), some of which need the above
   changes.

Change-Id: I09a72302bc1fd3635a326da92405222afa222e85
Reviewed-on: https://go-review.googlesource.com/c/go/+/291109
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 17 insertions, 8 deletions

diff --git a/test/typeparam/min.go b/test/typeparam/min.go
index 3bd92c5f3e..a3e4464a30 100644
--- a/test/typeparam/min.go
+++ b/test/typeparam/min.go
@@ -10,8 +10,11 @@ import (
 	"fmt"
 )
 
+type Ordered interface {
+	type int, int64, float64
+}
 
-func min[T interface{ type int }](x, y T) T {
+func min[T Ordered](x, y T) T {
 	if x < y {
 		return x
 	}
@@ -19,14 +22,20 @@ func min[T interface{ type int }](x, y T) T {
 }
 
 func main() {
-	want := 2
-	got := min[int](2, 3)
-	if want != got {
-		panic(fmt.Sprintf("Want %d, got %d", want, got))
+	const want = 2
+	if got := min[int](2, 3); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := min(2, 3); got != want {
+		panic(fmt.Sprintf("want %d, got %d", want, got))
+	}
+
+	if got := min[float64](3.5, 2.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
 	}
 
-	got = min(2, 3)
-	if want != got {
-		panic(fmt.Sprintf("Want %d, got %d", want, got))
+	if got := min(3.5, 2.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
 	}
 }