diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index 7a7c05280d..1626ab9dd3 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -565,10 +565,10 @@ func (subst *subster) list(l []ir.Node) []ir.Node {
 }
 
 // tstruct substitutes type params in types of the fields of a structure type. For
-// each field, if Nname is set, tstruct also translates the Nname using
-// subst.vars, if Nname is in subst.vars. To always force the creation of a new
-// (top-level) struct, regardless of whether anything changed with the types or
-// names of the struct's fields, set force to true.
+// each field, tstruct copies the Nname, and translates it if Nname is in
+// subst.vars. To always force the creation of a new (top-level) struct,
+// regardless of whether anything changed with the types or names of the struct's
+// fields, set force to true.
 func (subst *subster) tstruct(t *types.Type, force bool) *types.Type {
 	if t.NumFields() == 0 {
 		if t.HasTParam() {
@@ -597,15 +597,21 @@ func (subst *subster) tstruct(t *types.Type, force bool) *types.Type {
 			// the type param, not the instantiated type).
 			newfields[i] = types.NewField(f.Pos, f.Sym, t2)
 			if f.Nname != nil {
-				// f.Nname may not be in subst.vars[] if this is
-				// a function name or a function instantiation type
-				// that we are translating
 				v := subst.vars[f.Nname.(*ir.Name)]
-				// Be careful not to put a nil var into Nname,
-				// since Nname is an interface, so it would be a
-				// non-nil interface.
 				if v != nil {
+					// This is the case where we are
+					// translating the type of the function we
+					// are substituting, so its dcls are in
+					// the subst.vars table, and we want to
+					// change to reference the new dcl.
 					newfields[i].Nname = v
+				} else {
+					// This is the case where we are
+					// translating the type of a function
+					// reference inside the function we are
+					// substituting, so we leave the Nname
+					// value as is.
+					newfields[i].Nname = f.Nname
 				}
 			}
 		}
diff --git a/test/typeparam/sliceimp.dir/a.go b/test/typeparam/sliceimp.dir/a.go
new file mode 100644
index 0000000000..2b58d1c29e
--- /dev/null
+++ b/test/typeparam/sliceimp.dir/a.go
@@ -0,0 +1,141 @@
+// 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 Ordered interface {
+        type int, int8, int16, int32, int64,
+                uint, uint8, uint16, uint32, uint64, uintptr,
+                float32, float64,
+                string
+}
+
+// Max returns the maximum of two values of some ordered type.
+func Max[T Ordered](a, b T) T {
+        if a > b {
+                return a
+        }
+        return b
+}
+
+// Min returns the minimum of two values of some ordered type.
+func Min[T Ordered](a, b T) T {
+        if a < b {
+                return a
+        }
+        return b
+}
+
+// Equal reports whether two slices are equal: the same length and all
+// elements equal. All floating point NaNs are considered equal.
+func Equal[Elem comparable](s1, s2 []Elem) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// EqualFn reports whether two slices are equal using a comparision
+// function on each element.
+func EqualFn[Elem any](s1, s2 []Elem, eq func(Elem, Elem) bool) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if !eq(v1, v2) {
+			return false
+		}
+	}
+	return true
+}
+
+// Map turns a []Elem1 to a []Elem2 using a mapping function.
+func Map[Elem1, Elem2 any](s []Elem1, f func(Elem1) Elem2) []Elem2 {
+	r := make([]Elem2, len(s))
+	for i, v := range s {
+		r[i] = f(v)
+	}
+	return r
+}
+
+// Reduce reduces a []Elem1 to a single value of type Elem2 using
+// a reduction function.
+func Reduce[Elem1, Elem2 any](s []Elem1, initializer Elem2, f func(Elem2, Elem1) Elem2) Elem2 {
+	r := initializer
+	for _, v := range s {
+		r = f(r, v)
+	}
+	return r
+}
+
+// Filter filters values from a slice using a filter function.
+func Filter[Elem any](s []Elem, f func(Elem) bool) []Elem {
+	var r []Elem
+	for _, v := range s {
+		if f(v) {
+			r = append(r, v)
+		}
+	}
+	return r
+}
+
+// Max returns the maximum element in a slice of some ordered type.
+// If the slice is empty it returns the zero value of the element type.
+func SliceMax[Elem Ordered](s []Elem) Elem {
+	if len(s) == 0 {
+		var zero Elem
+		return zero
+	}
+	return Reduce(s[1:], s[0], Max[Elem])
+}
+
+// Min returns the minimum element in a slice of some ordered type.
+// If the slice is empty it returns the zero value of the element type.
+func SliceMin[Elem Ordered](s []Elem) Elem {
+	if len(s) == 0 {
+		var zero Elem
+		return zero
+	}
+	return Reduce(s[1:], s[0], Min[Elem])
+}
+
+// Append adds values to the end of a slice, returning a new slice.
+// This is like the predeclared append function; it's an example
+// of how to write it using generics. We used to write code like
+// this before append was added to the language, but we had to write
+// a separate copy for each type.
+func Append[T any](s []T, t ...T) []T {
+	lens := len(s)
+	tot := lens + len(t)
+	if tot <= cap(s) {
+		s = s[:tot]
+	} else {
+		news := make([]T, tot, tot + tot/2)
+		Copy(news, s)
+		s = news
+	}
+	Copy(s[lens:tot], t)
+	return s
+}
+
+// Copy copies values from t to s, stopping when either slice is full,
+// returning the number of values copied. This is like the predeclared
+// copy function; it's an example of how to write it using generics.
+func Copy[T any](s, t []T) int {
+	i := 0
+	for ; i < len(s) && i < len(t); i++ {
+		s[i] = t[i]
+	}
+	return i
+}
diff --git a/test/typeparam/sliceimp.dir/main.go b/test/typeparam/sliceimp.dir/main.go
new file mode 100644
index 0000000000..0a8e756b26
--- /dev/null
+++ b/test/typeparam/sliceimp.dir/main.go
@@ -0,0 +1,179 @@
+// 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"
+	"fmt"
+	"math"
+	"strings"
+)
+
+type Integer interface {
+        type int, int8, int16, int32, int64,
+                uint, uint8, uint16, uint32, uint64, uintptr
+}
+
+func TestEqual() {
+        s1 := []int{1, 2, 3}
+        if !a.Equal(s1, s1) {
+                panic(fmt.Sprintf("a.Equal(%v, %v) = false, want true", s1, s1))
+        }
+        s2 := []int{1, 2, 3}
+        if !a.Equal(s1, s2) {
+                panic(fmt.Sprintf("a.Equal(%v, %v) = false, want true", s1, s2))
+        }
+        s2 = append(s2, 4)
+        if a.Equal(s1, s2) {
+                panic(fmt.Sprintf("a.Equal(%v, %v) = true, want false", s1, s2))
+        }
+
+        s3 := []float64{1, 2, math.NaN()}
+        if !a.Equal(s3, s3) {
+                panic(fmt.Sprintf("a.Equal(%v, %v) = false, want true", s3, s3))
+        }
+
+        if a.Equal(s1, nil) {
+                panic(fmt.Sprintf("a.Equal(%v, nil) = true, want false", s1))
+        }
+        if a.Equal(nil, s1) {
+                panic(fmt.Sprintf("a.Equal(nil, %v) = true, want false", s1))
+        }
+        if !a.Equal(s1[:0], nil) {
+                panic(fmt.Sprintf("a.Equal(%v, nil = false, want true", s1[:0]))
+        }
+}
+
+func offByOne[Elem Integer](a, b Elem) bool {
+	return a == b + 1 || a == b - 1
+}
+
+func TestEqualFn() {
+	s1 := []int{1, 2, 3}
+	s2 := []int{2, 3, 4}
+	if a.EqualFn(s1, s1, offByOne[int]) {
+		panic(fmt.Sprintf("a.EqualFn(%v, %v, offByOne) = true, want false", s1, s1))
+	}
+	if !a.EqualFn(s1, s2, offByOne[int]) {
+		panic(fmt.Sprintf("a.EqualFn(%v, %v, offByOne) = false, want true", s1, s2))
+	}
+
+	if !a.EqualFn(s1[:0], nil, offByOne[int]) {
+		panic(fmt.Sprintf("a.EqualFn(%v, nil, offByOne) = false, want true", s1[:0]))
+	}
+
+	s3 := []string{"a", "b", "c"}
+	s4 := []string{"A", "B", "C"}
+	if !a.EqualFn(s3, s4, strings.EqualFold) {
+		panic(fmt.Sprintf("a.EqualFn(%v, %v, strings.EqualFold) = false, want true", s3, s4))
+	}
+}
+
+func TestMap() {
+	s1 := []int{1, 2, 3}
+	s2 := a.Map(s1, func(i int) float64 { return float64(i) * 2.5 })
+	if want := []float64{2.5, 5, 7.5}; !a.Equal(s2, want) {
+		panic(fmt.Sprintf("a.Map(%v, ...) = %v, want %v", s1, s2, want))
+	}
+
+	s3 := []string{"Hello", "World"}
+	s4 := a.Map(s3, strings.ToLower)
+	if want := []string{"hello", "world"}; !a.Equal(s4, want) {
+		panic(fmt.Sprintf("a.Map(%v, strings.ToLower) = %v, want %v", s3, s4, want))
+	}
+
+	s5 := a.Map(nil, func(i int) int { return i })
+	if len(s5) != 0 {
+		panic(fmt.Sprintf("a.Map(nil, identity) = %v, want empty slice", s5))
+	}
+}
+
+func TestReduce() {
+	s1 := []int{1, 2, 3}
+	r := a.Reduce(s1, 0, func(f float64, i int) float64 { return float64(i) * 2.5 + f })
+	if want := 15.0; r != want {
+		panic(fmt.Sprintf("a.Reduce(%v, 0, ...) = %v, want %v", s1, r, want))
+	}
+
+	if got := a.Reduce(nil, 0, func(i, j int) int { return i + j}); got != 0 {
+		panic(fmt.Sprintf("a.Reduce(nil, 0, add) = %v, want 0", got))
+	}
+}
+
+func TestFilter() {
+	s1 := []int{1, 2, 3}
+	s2 := a.Filter(s1, func(i int) bool { return i%2 == 0 })
+	if want := []int{2}; !a.Equal(s2, want) {
+		panic(fmt.Sprintf("a.Filter(%v, even) = %v, want %v", s1, s2, want))
+	}
+
+	if s3 := a.Filter(s1[:0], func(i int) bool { return true }); len(s3) > 0 {
+		panic(fmt.Sprintf("a.Filter(%v, identity) = %v, want empty slice", s1[:0], s3))
+	}
+}
+
+func TestMax() {
+	s1 := []int{1, 2, 3, -5}
+	if got, want := a.SliceMax(s1), 3; got != want {
+		panic(fmt.Sprintf("a.Max(%v) = %d, want %d", s1, got, want))
+	}
+
+	s2 := []string{"aaa", "a", "aa", "aaaa"}
+	if got, want := a.SliceMax(s2), "aaaa"; got != want {
+		panic(fmt.Sprintf("a.Max(%v) = %q, want %q", s2, got, want))
+	}
+
+	if got, want := a.SliceMax(s2[:0]), ""; got != want {
+		panic(fmt.Sprintf("a.Max(%v) = %q, want %q", s2[:0], got, want))
+	}
+}
+
+func TestMin() {
+	s1 := []int{1, 2, 3, -5}
+	if got, want := a.SliceMin(s1), -5; got != want {
+		panic(fmt.Sprintf("a.Min(%v) = %d, want %d", s1, got, want))
+	}
+
+	s2 := []string{"aaa", "a", "aa", "aaaa"}
+	if got, want := a.SliceMin(s2), "a"; got != want {
+		panic(fmt.Sprintf("a.Min(%v) = %q, want %q", s2, got, want))
+	}
+
+	if got, want := a.SliceMin(s2[:0]), ""; got != want {
+		panic(fmt.Sprintf("a.Min(%v) = %q, want %q", s2[:0], got, want))
+	}
+}
+
+func TestAppend() {
+	s := []int{1, 2, 3}
+	s = a.Append(s, 4, 5, 6)
+	want := []int{1, 2, 3, 4, 5, 6}
+	if !a.Equal(s, want) {
+		panic(fmt.Sprintf("after a.Append got %v, want %v", s, want))
+	}
+}
+
+func TestCopy() {
+	s1 := []int{1, 2, 3}
+	s2 := []int{4, 5}
+	if got := a.Copy(s1, s2); got != 2 {
+		panic(fmt.Sprintf("a.Copy returned %d, want 2", got))
+	}
+	want := []int{4, 5, 3}
+	if !a.Equal(s1, want) {
+		panic(fmt.Sprintf("after a.Copy got %v, want %v", s1, want))
+	}
+}
+func main() {
+	TestEqual()
+	TestEqualFn()
+	TestMap()
+	TestReduce()
+	TestFilter()
+	TestMax()
+	TestMin()
+	TestAppend()
+	TestCopy()
+}
diff --git a/test/typeparam/sliceimp.go b/test/typeparam/sliceimp.go
new file mode 100644
index 0000000000..76930e5e4f
--- /dev/null
+++ b/test/typeparam/sliceimp.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