1 files changed, 69 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/types2/typelists.go b/src/cmd/compile/internal/types2/typelists.go
new file mode 100644
index 0000000000..3258a5e9f8
--- /dev/null
+++ b/src/cmd/compile/internal/types2/typelists.go
@@ -0,0 +1,69 @@
+// 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 types2
+
+// TParamList holds a list of type parameters.
+type TParamList struct{ tparams []*TypeParam }
+
+// Len returns the number of type parameters in the list.
+// It is safe to call on a nil receiver.
+func (l *TParamList) Len() int { return len(l.list()) }
+
+// At returns the i'th type parameter in the list.
+func (l *TParamList) At(i int) *TypeParam { return l.tparams[i] }
+
+// list is for internal use where we expect a []*TypeParam.
+// TODO(rfindley): list should probably be eliminated: we can pass around a
+// TParamList instead.
+func (l *TParamList) list() []*TypeParam {
+	if l == nil {
+		return nil
+	}
+	return l.tparams
+}
+
+// TypeList holds a list of types.
+type TypeList struct{ types []Type }
+
+// NewTypeList returns a new TypeList with the types in list.
+func NewTypeList(list []Type) *TypeList {
+	if len(list) == 0 {
+		return nil
+	}
+	return &TypeList{list}
+}
+
+// Len returns the number of types in the list.
+// It is safe to call on a nil receiver.
+func (l *TypeList) Len() int { return len(l.list()) }
+
+// At returns the i'th type in the list.
+func (l *TypeList) At(i int) Type { return l.types[i] }
+
+// list is for internal use where we expect a []Type.
+// TODO(rfindley): list should probably be eliminated: we can pass around a
+// TypeList instead.
+func (l *TypeList) list() []Type {
+	if l == nil {
+		return nil
+	}
+	return l.types
+}
+
+// ----------------------------------------------------------------------------
+// Implementation
+
+func bindTParams(list []*TypeParam) *TParamList {
+	if len(list) == 0 {
+		return nil
+	}
+	for i, typ := range list {
+		if typ.index >= 0 {
+			panic("type parameter bound more than once")
+		}
+		typ.index = i
+	}
+	return &TParamList{tparams: list}
+}