1 files changed, 163 insertions, 0 deletions
diff --git a/libgo/go/go/types/typeparam.go b/libgo/go/go/types/typeparam.go
new file mode 100644
index 00000000000..03ba9be55c5
--- /dev/null
+++ b/libgo/go/go/types/typeparam.go
@@ -0,0 +1,163 @@
+// Copyright 2011 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 types
+
+import (
+	"go/token"
+	"sync/atomic"
+)
+
+// Note: This is a uint32 rather than a uint64 because the
+// respective 64 bit atomic instructions are not available
+// on all platforms.
+var lastID uint32
+
+// nextID returns a value increasing monotonically by 1 with
+// each call, starting with 1. It may be called concurrently.
+func nextID() uint64 { return uint64(atomic.AddUint32(&lastID, 1)) }
+
+// A TypeParam represents a type parameter type.
+type TypeParam struct {
+	check *Checker  // for lazy type bound completion
+	id    uint64    // unique id, for debugging only
+	obj   *TypeName // corresponding type name
+	index int       // type parameter index in source order, starting at 0
+	bound Type      // any type, but underlying is eventually *Interface for correct programs (see TypeParam.iface)
+}
+
+// NewTypeParam returns a new TypeParam. Type parameters may be set on a Named
+// or Signature type by calling SetTypeParams. Setting a type parameter on more
+// than one type will result in a panic.
+//
+// The constraint argument can be nil, and set later via SetConstraint.
+func NewTypeParam(obj *TypeName, constraint Type) *TypeParam {
+	return (*Checker)(nil).newTypeParam(obj, constraint)
+}
+
+func (check *Checker) newTypeParam(obj *TypeName, constraint Type) *TypeParam {
+	// Always increment lastID, even if it is not used.
+	id := nextID()
+	if check != nil {
+		check.nextID++
+		id = check.nextID
+	}
+	typ := &TypeParam{check: check, id: id, obj: obj, index: -1, bound: constraint}
+	if obj.typ == nil {
+		obj.typ = typ
+	}
+	// iface may mutate typ.bound, so we must ensure that iface() is called
+	// at least once before the resulting TypeParam escapes.
+	if check != nil {
+		check.later(func() {
+			typ.iface()
+		})
+	} else if constraint != nil {
+		typ.iface()
+	}
+	return typ
+}
+
+// Index returns the index of the type param within its param list, or -1 if
+// the type parameter has not yet been bound to a type.
+func (t *TypeParam) Index() int {
+	return t.index
+}
+
+// Obj returns the type name for t.
+func (t *TypeParam) Obj() *TypeName { return t.obj }
+
+// Constraint returns the type constraint specified for t.
+func (t *TypeParam) Constraint() Type {
+	return t.bound
+}
+
+// SetConstraint sets the type constraint for t.
+//
+// SetConstraint should not be called concurrently, but once SetConstraint
+// returns the receiver t is safe for concurrent use.
+func (t *TypeParam) SetConstraint(bound Type) {
+	if bound == nil {
+		panic("nil constraint")
+	}
+	t.bound = bound
+	// iface may mutate t.bound (if bound is not an interface), so ensure that
+	// this is done before returning.
+	t.iface()
+}
+
+func (t *TypeParam) Underlying() Type {
+	return t.iface()
+}
+
+func (t *TypeParam) String() string { return TypeString(t, nil) }
+
+// ----------------------------------------------------------------------------
+// Implementation
+
+// iface returns the constraint interface of t.
+// TODO(gri) If we make tparamIsIface the default, this should be renamed to under
+//           (similar to Named.under).
+func (t *TypeParam) iface() *Interface {
+	bound := t.bound
+
+	// determine constraint interface
+	var ityp *Interface
+	switch u := under(bound).(type) {
+	case *Basic:
+		if u == Typ[Invalid] {
+			// error is reported elsewhere
+			return &emptyInterface
+		}
+	case *Interface:
+		if isTypeParam(bound) {
+			// error is reported in Checker.collectTypeParams
+			return &emptyInterface
+		}
+		ityp = u
+	}
+
+	// If we don't have an interface, wrap constraint into an implicit interface.
+	if ityp == nil {
+		ityp = NewInterfaceType(nil, []Type{bound})
+		ityp.implicit = true
+		t.bound = ityp // update t.bound for next time (optimization)
+	}
+
+	// compute type set if necessary
+	if ityp.tset == nil {
+		// use the (original) type bound position if we have one
+		pos := token.NoPos
+		if n, _ := bound.(*Named); n != nil {
+			pos = n.obj.pos
+		}
+		computeInterfaceTypeSet(t.check, pos, ityp)
+	}
+
+	return ityp
+}
+
+// singleType returns the single type of the type parameter constraint; or nil.
+func (t *TypeParam) singleType() Type {
+	return t.iface().typeSet().singleType()
+}
+
+// hasTerms reports whether the type parameter constraint has specific type terms.
+func (t *TypeParam) hasTerms() bool {
+	return t.iface().typeSet().hasTerms()
+}
+
+// is calls f with the specific type terms of t's constraint and reports whether
+// all calls to f returned true. If there are no specific terms, is
+// returns the result of f(nil).
+func (t *TypeParam) is(f func(*term) bool) bool {
+	return t.iface().typeSet().is(f)
+}
+
+// underIs calls f with the underlying types of the specific type terms
+// of t's constraint and reports whether all calls to f returned true.
+// If there are no specific terms, underIs returns the result of f(nil).
+func (t *TypeParam) underIs(f func(Type) bool) bool {
+	return t.iface().typeSet().underIs(f)
+}