test: re-enabled fixedbugs/notinheap.go test

By using cgo.Incomplete to represent not-in-heap type.

While at it, also removing the type conversions tests, since they could
not be present without //go:notinheap pragma.

Fixes #54846

Change-Id: I5ee2a4b6498d4100c9770ed7bd62f52623e42526
Reviewed-on: https://go-review.googlesource.com/c/go/+/597536
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>

2 files changed, 6 insertions, 27 deletions

diff --git a/src/cmd/internal/testdir/testdir_test.go b/src/cmd/internal/testdir/testdir_test.go
index 8d68591982..e64451b743 100644
--- a/src/cmd/internal/testdir/testdir_test.go
+++ b/src/cmd/internal/testdir/testdir_test.go
@@ -1859,7 +1859,6 @@ var types2Failures = setOf(
 	"fixedbugs/issue20233.go", // types2 reports two instead of one error (preference: 1.17 compiler)
 	"fixedbugs/issue20245.go", // types2 reports two instead of one error (preference: 1.17 compiler)
 	"fixedbugs/issue31053.go", // types2 reports "unknown field" instead of "cannot refer to unexported field"
-	"fixedbugs/notinheap.go",  // types2 doesn't report errors about conversions that are invalid due to //go:notinheap
 )
 
 var types2Failures32Bit = setOf(
diff --git a/test/fixedbugs/notinheap.go b/test/fixedbugs/notinheap.go
index 2188a38a14..bb13456211 100644
--- a/test/fixedbugs/notinheap.go
+++ b/test/fixedbugs/notinheap.go
@@ -4,12 +4,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Test type-checking errors for go:notinheap.
+// Test type-checking errors for not-in-heap types.
+
+//go:build cgo
 
 package p
 
-//go:notinheap
-type nih struct{}
+import "runtime/cgo"
+
+type nih struct{ _ cgo.Incomplete }
 
 type embed4 map[nih]int // ERROR "incomplete \(or unallocatable\) map key not allowed"
 
@@ -26,26 +29,3 @@ type okay3 func(x nih) nih
 type okay4 interface {
 	f(x nih) nih
 }
-
-// Type conversions don't let you sneak past notinheap.
-
-type t1 struct{ x int }
-
-//go:notinheap
-type t2 t1
-
-//go:notinheap
-type t3 byte
-
-//go:notinheap
-type t4 rune
-
-var sink interface{}
-
-func i() {
-	sink = new(t1)                     // no error
-	sink = (*t2)(new(t1))              // ERROR "cannot convert(.|\n)*t2 is incomplete \(or unallocatable\)"
-	sink = (*t2)(new(struct{ x int })) // ERROR "cannot convert(.|\n)*t2 is incomplete \(or unallocatable\)"
-	sink = []t3("foo")                 // ERROR "cannot convert(.|\n)*t3 is incomplete \(or unallocatable\)"
-	sink = []t4("bar")                 // ERROR "cannot convert(.|\n)*t4 is incomplete \(or unallocatable\)"
-}