[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, 8 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ir/expr.go b/src/cmd/compile/internal/ir/expr.go
index 9c800dcd1a..09d6d87f06 100644
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@@ -349,6 +349,14 @@ func (n *InlinedCallExpr) SingleResult() Node {
 	if have := len(n.ReturnVars); have != 1 {
 		base.FatalfAt(n.Pos(), "inlined call has %v results, expected 1", have)
 	}
+	if !n.Type().HasShape() && n.ReturnVars[0].Type().HasShape() {
+		// If the type of the call is not a shape, but the type of the return value
+		// is a shape, we need to do an implicit conversion, so the real type
+		// of n is maintained.
+		r := NewConvExpr(n.Pos(), OCONVNOP, n.Type(), n.ReturnVars[0])
+		r.SetTypecheck(1)
+		return r
+	}
 	return n.ReturnVars[0]
 }