diff --git a/test/run.go b/test/run.go
index ff8bf4b229..df3befbf21 100644
--- a/test/run.go
+++ b/test/run.go
@@ -86,7 +86,7 @@ var (
 
 	// dirs are the directories to look for *.go files in.
 	// TODO(bradfitz): just use all directories?
-	dirs = []string{".", "ken", "chan", "interface", "syntax", "dwarf", "fixedbugs", "codegen", "runtime", "abi", "typeparam"}
+	dirs = []string{".", "ken", "chan", "interface", "syntax", "dwarf", "fixedbugs", "codegen", "runtime", "abi", "typeparam", "typeparam/mdempsky"}
 
 	// ratec controls the max number of tests running at a time.
 	ratec chan bool
@@ -2203,6 +2203,19 @@ var g3Failures = setOf(
 	"fixedbugs/issue9691.go", // "cannot assign to int(.autotmp_4)" (probably irgen's fault)
 
 	"typeparam/nested.go", // -G=3 doesn't support function-local types with generics
+
+	"typeparam/mdempsky/1.go",
+	"typeparam/mdempsky/2.go",
+	"typeparam/mdempsky/3.go",
+	"typeparam/mdempsky/4.go",
+	"typeparam/mdempsky/5.go",
+	"typeparam/mdempsky/7.go",
+	"typeparam/mdempsky/8.go",
+	"typeparam/mdempsky/9.go",
+	"typeparam/mdempsky/11.go",
+	"typeparam/mdempsky/12.go",
+	"typeparam/mdempsky/13.go",
+	"typeparam/mdempsky/14.go",
 )
 
 var unifiedFailures = setOf(
diff --git a/test/typeparam/mdempsky/1.dir/a.go b/test/typeparam/mdempsky/1.dir/a.go
new file mode 100644
index 0000000000..a668eb52dc
--- /dev/null
+++ b/test/typeparam/mdempsky/1.dir/a.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type T[_ any] int
+
+func F() { _ = new(T[int]) }
diff --git a/test/typeparam/mdempsky/1.dir/b.go b/test/typeparam/mdempsky/1.dir/b.go
new file mode 100644
index 0000000000..af6fef3f6d
--- /dev/null
+++ b/test/typeparam/mdempsky/1.dir/b.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+func main() { a.F() }
diff --git a/test/typeparam/mdempsky/1.go b/test/typeparam/mdempsky/1.go
new file mode 100644
index 0000000000..87b4ff46c1
--- /dev/null
+++ b/test/typeparam/mdempsky/1.go
@@ -0,0 +1,7 @@
+// compiledir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/10.dir/a.go b/test/typeparam/mdempsky/10.dir/a.go
new file mode 100644
index 0000000000..95e111d347
--- /dev/null
+++ b/test/typeparam/mdempsky/10.dir/a.go
@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type I[T any] interface{ M() T }
diff --git a/test/typeparam/mdempsky/10.dir/b.go b/test/typeparam/mdempsky/10.dir/b.go
new file mode 100644
index 0000000000..0ef28fd02d
--- /dev/null
+++ b/test/typeparam/mdempsky/10.dir/b.go
@@ -0,0 +1,17 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+var m = a.I[int].M
+
+var never bool
+
+func main() {
+	if never {
+		m(nil)
+	}
+}
diff --git a/test/typeparam/mdempsky/10.go b/test/typeparam/mdempsky/10.go
new file mode 100644
index 0000000000..76930e5e4f
--- /dev/null
+++ b/test/typeparam/mdempsky/10.go
@@ -0,0 +1,7 @@
+// rundir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/11.go b/test/typeparam/mdempsky/11.go
new file mode 100644
index 0000000000..e86c038a10
--- /dev/null
+++ b/test/typeparam/mdempsky/11.go
@@ -0,0 +1,16 @@
+// errorcheck
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Reported by Cuong Manh Le.
+
+package p
+
+type a struct{}
+
+//go:notinheap
+type b a
+
+var _ = (*b)(new(a)) // ERROR "cannot convert"
diff --git a/test/typeparam/mdempsky/12.dir/a.go b/test/typeparam/mdempsky/12.dir/a.go
new file mode 100644
index 0000000000..ee8be939a8
--- /dev/null
+++ b/test/typeparam/mdempsky/12.dir/a.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type S[T any] struct {
+	F T
+}
+
+var X = S[int]{}
diff --git a/test/typeparam/mdempsky/12.dir/main.go b/test/typeparam/mdempsky/12.dir/main.go
new file mode 100644
index 0000000000..2891322e29
--- /dev/null
+++ b/test/typeparam/mdempsky/12.dir/main.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"./a"
+)
+
+func main() {
+	_ = a.X
+}
diff --git a/test/typeparam/mdempsky/12.go b/test/typeparam/mdempsky/12.go
new file mode 100644
index 0000000000..a2dc4daacc
--- /dev/null
+++ b/test/typeparam/mdempsky/12.go
@@ -0,0 +1,9 @@
+// rundir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Reported by Cuong Manh Le.
+
+package ignored
diff --git a/test/typeparam/mdempsky/13.go b/test/typeparam/mdempsky/13.go
new file mode 100644
index 0000000000..dc1d29bce1
--- /dev/null
+++ b/test/typeparam/mdempsky/13.go
@@ -0,0 +1,38 @@
+// run -gcflags=-G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Mer interface{ M() }
+
+func F[T Mer](expectPanic bool) {
+	defer func() {
+		err := recover()
+		if (err != nil) != expectPanic {
+			print("FAIL: (", err, " != nil) != ", expectPanic, "\n")
+		}
+	}()
+
+	var t T
+	T.M(t)
+}
+
+type MyMer int
+
+func (MyMer) M() {}
+
+func main() {
+	F[Mer](true)
+	F[struct{ Mer }](true)
+	F[*struct{ Mer }](true)
+
+	F[MyMer](false)
+	F[*MyMer](true)
+	F[struct{ MyMer }](false)
+	F[struct{ *MyMer }](true)
+	F[*struct{ MyMer }](true)
+	F[*struct{ *MyMer }](true)
+}
diff --git a/test/typeparam/mdempsky/14.go b/test/typeparam/mdempsky/14.go
new file mode 100644
index 0000000000..61f9436910
--- /dev/null
+++ b/test/typeparam/mdempsky/14.go
@@ -0,0 +1,37 @@
+// run -gcflags=-G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func Zero[T any]() (_ T) { return }
+
+type T[X any] int
+
+func (T[X]) M() {
+	var have interface{} = Zero[X]()
+	var want interface{} = Zero[MyInt]()
+
+	if have != want {
+		println("FAIL")
+	}
+}
+
+type I interface{ M() }
+
+type MyInt int
+type U = T[MyInt]
+
+var x = U(0)
+var i I = x
+
+func main() {
+	x.M()
+	U.M(x)
+	(*U).M(&x)
+
+	i.M()
+	I.M(x)
+}
diff --git a/test/typeparam/mdempsky/2.go b/test/typeparam/mdempsky/2.go
new file mode 100644
index 0000000000..f09730f949
--- /dev/null
+++ b/test/typeparam/mdempsky/2.go
@@ -0,0 +1,20 @@
+// compile -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type T[A, B, C any] int
+
+func (T[A, B, C]) m(x int) {
+	if x <= 0 {
+		return
+	}
+	T[B, C, A](0).m(x - 1)
+}
+
+func main() {
+	T[int8, int16, int32](0).m(3)
+}
diff --git a/test/typeparam/mdempsky/3.dir/a.go b/test/typeparam/mdempsky/3.dir/a.go
new file mode 100644
index 0000000000..cf456e8d48
--- /dev/null
+++ b/test/typeparam/mdempsky/3.dir/a.go
@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+func F[T interface{ chan int }](c T) {}
diff --git a/test/typeparam/mdempsky/3.dir/b.go b/test/typeparam/mdempsky/3.dir/b.go
new file mode 100644
index 0000000000..0cfd142f4c
--- /dev/null
+++ b/test/typeparam/mdempsky/3.dir/b.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+func g() { a.F(make(chan int)) }
diff --git a/test/typeparam/mdempsky/3.go b/test/typeparam/mdempsky/3.go
new file mode 100644
index 0000000000..87b4ff46c1
--- /dev/null
+++ b/test/typeparam/mdempsky/3.go
@@ -0,0 +1,7 @@
+// compiledir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/4.dir/a.go b/test/typeparam/mdempsky/4.dir/a.go
new file mode 100644
index 0000000000..cb672949ea
--- /dev/null
+++ b/test/typeparam/mdempsky/4.dir/a.go
@@ -0,0 +1,12 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+func F[T any](T) {
+Loop:
+	for {
+		break Loop
+	}
+}
diff --git a/test/typeparam/mdempsky/4.dir/b.go b/test/typeparam/mdempsky/4.dir/b.go
new file mode 100644
index 0000000000..e1fb0e7c5e
--- /dev/null
+++ b/test/typeparam/mdempsky/4.dir/b.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+func f() { a.F(0) }
diff --git a/test/typeparam/mdempsky/4.go b/test/typeparam/mdempsky/4.go
new file mode 100644
index 0000000000..87b4ff46c1
--- /dev/null
+++ b/test/typeparam/mdempsky/4.go
@@ -0,0 +1,7 @@
+// compiledir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/5.go b/test/typeparam/mdempsky/5.go
new file mode 100644
index 0000000000..0d1ad39946
--- /dev/null
+++ b/test/typeparam/mdempsky/5.go
@@ -0,0 +1,15 @@
+// compile -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type X[T any] int
+
+func (X[T]) F(T) {}
+
+func x() {
+	X[interface{}](0).F(0)
+}
diff --git a/test/typeparam/mdempsky/6.go b/test/typeparam/mdempsky/6.go
new file mode 100644
index 0000000000..a26ff62f6d
--- /dev/null
+++ b/test/typeparam/mdempsky/6.go
@@ -0,0 +1,11 @@
+// compile -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type I[T any] interface{ M() T }
+
+var _ = I[int].M
diff --git a/test/typeparam/mdempsky/7.dir/a.go b/test/typeparam/mdempsky/7.dir/a.go
new file mode 100644
index 0000000000..59c5995611
--- /dev/null
+++ b/test/typeparam/mdempsky/7.dir/a.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type I[T any] interface{ M() T }
+
+var X I[int]
diff --git a/test/typeparam/mdempsky/7.dir/b.go b/test/typeparam/mdempsky/7.dir/b.go
new file mode 100644
index 0000000000..9f70530811
--- /dev/null
+++ b/test/typeparam/mdempsky/7.dir/b.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+var _ = a.X
diff --git a/test/typeparam/mdempsky/7.go b/test/typeparam/mdempsky/7.go
new file mode 100644
index 0000000000..87b4ff46c1
--- /dev/null
+++ b/test/typeparam/mdempsky/7.go
@@ -0,0 +1,7 @@
+// compiledir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/8.dir/a.go b/test/typeparam/mdempsky/8.dir/a.go
new file mode 100644
index 0000000000..607fe5e0af
--- /dev/null
+++ b/test/typeparam/mdempsky/8.dir/a.go
@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+func F[T interface{ comparable }]() {}
diff --git a/test/typeparam/mdempsky/8.dir/b.go b/test/typeparam/mdempsky/8.dir/b.go
new file mode 100644
index 0000000000..ef2637b894
--- /dev/null
+++ b/test/typeparam/mdempsky/8.dir/b.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+func init() {
+	a.F[func()]() // ERROR "does not satisfy comparable"
+}
diff --git a/test/typeparam/mdempsky/8.go b/test/typeparam/mdempsky/8.go
new file mode 100644
index 0000000000..32cf4b830d
--- /dev/null
+++ b/test/typeparam/mdempsky/8.go
@@ -0,0 +1,7 @@
+// errorcheckdir -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored
diff --git a/test/typeparam/mdempsky/9.go b/test/typeparam/mdempsky/9.go
new file mode 100644
index 0000000000..b72516c4ea
--- /dev/null
+++ b/test/typeparam/mdempsky/9.go
@@ -0,0 +1,11 @@
+// compile -G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+func f[V any]() []V { return []V{0: *new(V)} }
+
+func g() { f[int]() }