[dev.typeparams] cmd/compile/internal/types2: parameterized functions must have a body

Add the respective check and add missing bodies to tests.
Use {} as body for functions that don't return a result.
Use { panic(0) } as body for functions that return a result.

For #47069.

Change-Id: Ia5d7525c9c036baf8a955d13bff448401e08235e
Reviewed-on: https://go-review.googlesource.com/c/go/+/340911
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/cmd/compile/internal/types2/testdata/check/issues.go2 b/src/cmd/compile/internal/types2/testdata/check/issues.go2
index 1ede383ebe..effc2db7ae 100644
--- a/src/cmd/compile/internal/types2/testdata/check/issues.go2
+++ b/src/cmd/compile/internal/types2/testdata/check/issues.go2
@@ -40,7 +40,7 @@ func _[T interface{ m() }](x *T) {
 	x.m /* ERROR x\.m undefined */ ()
 }
 
-func f2[_ interface{ m1(); m2() }]()
+func f2[_ interface{ m1(); m2() }]() {}
 
 type T struct{}
 func (T) m1()
@@ -232,7 +232,7 @@ func _[T interface{ ~func() }](f T) {
 
 type sliceOf[E any] interface{ ~[]E }
 
-func append[T interface{}, S sliceOf[T], T2 interface{}](s S, t ...T2) S
+func append[T interface{}, S sliceOf[T], T2 interface{}](s S, t ...T2) S { panic(0) }
 
 var f           func()
 var cancelSlice []context.CancelFunc
@@ -240,7 +240,7 @@ var _ = append[context.CancelFunc, []context.CancelFunc, context.CancelFunc](can
 
 // A generic function must be instantiated with a type, not a value.
 
-func g[T any](T) T
+func g[T any](T) T { panic(0) }
 
 var _ = g[int]
 var _ = g[nil /* ERROR is not a type */ ]