[dev.typeparams] go/types: move (remaining) type decls into their own files (cleanup)

This is a port of CL 332093 to go/types. A missing comment is added to
named.go, and some TODOs were added to converge on the TypeParam API.

Change-Id: I781a1d0d3fc6c11bb323123e954c106094d998ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/335040
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/array.go

@@ -0,0 +1,25 @@
+// 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
+
+// An Array represents an array type.
+type Array struct {
+	len  int64
+	elem Type
+}
+
+// NewArray returns a new array type for the given element type and length.
+// A negative length indicates an unknown length.
+func NewArray(elem Type, len int64) *Array { return &Array{len: len, elem: elem} }
+
+// Len returns the length of array a.
+// A negative result indicates an unknown length.
+func (a *Array) Len() int64 { return a.len }
+
+// Elem returns element type of array a.
+func (a *Array) Elem() Type { return a.elem }
+
+func (t *Array) Underlying() Type { return t }
+func (t *Array) String() string   { return TypeString(t, nil) }

src/go/types/basic.go

@@ -0,0 +1,82 @@
+// 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
+
+// BasicKind describes the kind of basic type.
+type BasicKind int
+
+const (
+	Invalid BasicKind = iota // type is invalid
+
+	// predeclared types
+	Bool
+	Int
+	Int8
+	Int16
+	Int32
+	Int64
+	Uint
+	Uint8
+	Uint16
+	Uint32
+	Uint64
+	Uintptr
+	Float32
+	Float64
+	Complex64
+	Complex128
+	String
+	UnsafePointer
+
+	// types for untyped values
+	UntypedBool
+	UntypedInt
+	UntypedRune
+	UntypedFloat
+	UntypedComplex
+	UntypedString
+	UntypedNil
+
+	// aliases
+	Byte = Uint8
+	Rune = Int32
+)
+
+// BasicInfo is a set of flags describing properties of a basic type.
+type BasicInfo int
+
+// Properties of basic types.
+const (
+	IsBoolean BasicInfo = 1 << iota
+	IsInteger
+	IsUnsigned
+	IsFloat
+	IsComplex
+	IsString
+	IsUntyped
+
+	IsOrdered   = IsInteger | IsFloat | IsString
+	IsNumeric   = IsInteger | IsFloat | IsComplex
+	IsConstType = IsBoolean | IsNumeric | IsString
+)
+
+// A Basic represents a basic type.
+type Basic struct {
+	kind BasicKind
+	info BasicInfo
+	name string
+}
+
+// Kind returns the kind of basic type b.
+func (b *Basic) Kind() BasicKind { return b.kind }
+
+// Info returns information about properties of basic type b.
+func (b *Basic) Info() BasicInfo { return b.info }
+
+// Name returns the name of basic type b.
+func (b *Basic) Name() string { return b.name }
+
+func (t *Basic) Underlying() Type { return t }
+func (t *Basic) String() string   { return TypeString(t, nil) }

src/go/types/chan.go

@@ -0,0 +1,35 @@
+// 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
+
+// A Chan represents a channel type.
+type Chan struct {
+	dir  ChanDir
+	elem Type
+}
+
+// A ChanDir value indicates a channel direction.
+type ChanDir int
+
+// The direction of a channel is indicated by one of these constants.
+const (
+	SendRecv ChanDir = iota
+	SendOnly
+	RecvOnly
+)
+
+// NewChan returns a new channel type for the given direction and element type.
+func NewChan(dir ChanDir, elem Type) *Chan {
+	return &Chan{dir: dir, elem: elem}
+}
+
+// Dir returns the direction of channel c.
+func (c *Chan) Dir() ChanDir { return c.dir }
+
+// Elem returns the element type of channel c.
+func (c *Chan) Elem() Type { return c.elem }
+
+func (t *Chan) Underlying() Type { return t }
+func (t *Chan) String() string   { return TypeString(t, nil) }

src/go/types/instance.go

@@ -0,0 +1,58 @@
+// 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"
+
+// An instance represents an instantiated generic type syntactically
+// (without expanding the instantiation). Type instances appear only
+// during type-checking and are replaced by their fully instantiated
+// (expanded) types before the end of type-checking.
+type instance struct {
+	check   *Checker    // for lazy instantiation
+	pos     token.Pos   // position of type instantiation; for error reporting only
+	base    *Named      // parameterized type to be instantiated
+	targs   []Type      // type arguments
+	poslist []token.Pos // position of each targ; for error reporting only
+	value   Type        // base(targs...) after instantiation or Typ[Invalid]; nil if not yet set
+}
+
+// expand returns the instantiated (= expanded) type of t.
+// The result is either an instantiated *Named type, or
+// Typ[Invalid] if there was an error.
+func (t *instance) expand() Type {
+	v := t.value
+	if v == nil {
+		v = t.check.instantiate(t.pos, t.base, t.targs, t.poslist)
+		if v == nil {
+			v = Typ[Invalid]
+		}
+		t.value = v
+	}
+	// After instantiation we must have an invalid or a *Named type.
+	if debug && v != Typ[Invalid] {
+		_ = v.(*Named)
+	}
+	return v
+}
+
+// expand expands a type instance into its instantiated
+// type and leaves all other types alone. expand does
+// not recurse.
+func expand(typ Type) Type {
+	if t, _ := typ.(*instance); t != nil {
+		return t.expand()
+	}
+	return typ
+}
+
+// expandf is set to expand.
+// Call expandf when calling expand causes compile-time cycle error.
+var expandf func(Type) Type
+
+func init() { expandf = expand }
+
+func (t *instance) Underlying() Type { return t }
+func (t *instance) String() string   { return TypeString(t, nil) }

src/go/types/map.go

@@ -0,0 +1,24 @@
+// 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
+
+// A Map represents a map type.
+type Map struct {
+	key, elem Type
+}
+
+// NewMap returns a new map for the given key and element types.
+func NewMap(key, elem Type) *Map {
+	return &Map{key: key, elem: elem}
+}
+
+// Key returns the key type of map m.
+func (m *Map) Key() Type { return m.key }
+
+// Elem returns the element type of map m.
+func (m *Map) Elem() Type { return m.elem }
+
+func (t *Map) Underlying() Type { return t }
+func (t *Map) String() string   { return TypeString(t, nil) }

src/go/types/named.go

@@ -0,0 +1,144 @@
+// 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 "sync"
+
+// TODO(rfindley) Clean up Named struct below; specifically the fromRHS field (can we use underlying?).
+
+// A Named represents a named (defined) type.
+type Named struct {
+	check      *Checker    // for Named.under implementation; nilled once under has been called
+	info       typeInfo    // for cycle detection
+	obj        *TypeName   // corresponding declared object
+	orig       *Named      // original, uninstantiated type
+	fromRHS    Type        // type (on RHS of declaration) this *Named type is derived of (for cycle reporting)
+	underlying Type        // possibly a *Named during setup; never a *Named once set up completely
+	tparams    []*TypeName // type parameters, or nil
+	targs      []Type      // type arguments (after instantiation), or nil
+	methods    []*Func     // methods declared for this type (not the method set of this type); signatures are type-checked lazily
+
+	resolve func(*Named) ([]*TypeName, Type, []*Func)
+	once    sync.Once
+}
+
+// NewNamed returns a new named type for the given type name, underlying type, and associated methods.
+// If the given type name obj doesn't have a type yet, its type is set to the returned named type.
+// The underlying type must not be a *Named.
+func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
+	if _, ok := underlying.(*Named); ok {
+		panic("types.NewNamed: underlying type must not be *Named")
+	}
+	return (*Checker)(nil).newNamed(obj, nil, underlying, nil, methods)
+}
+
+func (t *Named) expand() *Named {
+	if t.resolve == nil {
+		return t
+	}
+
+	t.once.Do(func() {
+		// TODO(mdempsky): Since we're passing t to resolve anyway
+		// (necessary because types2 expects the receiver type for methods
+		// on defined interface types to be the Named rather than the
+		// underlying Interface), maybe it should just handle calling
+		// SetTParams, SetUnderlying, and AddMethod instead?  Those
+		// methods would need to support reentrant calls though.  It would
+		// also make the API more future-proof towards further extensions
+		// (like SetTParams).
+
+		tparams, underlying, methods := t.resolve(t)
+
+		switch underlying.(type) {
+		case nil, *Named:
+			panic("invalid underlying type")
+		}
+
+		t.tparams = tparams
+		t.underlying = underlying
+		t.methods = methods
+	})
+	return t
+}
+
+// newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
+func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tparams []*TypeName, methods []*Func) *Named {
+	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, tparams: tparams, methods: methods}
+	if typ.orig == nil {
+		typ.orig = typ
+	}
+	if obj.typ == nil {
+		obj.typ = typ
+	}
+	// Ensure that typ is always expanded, at which point the check field can be
+	// nilled out.
+	//
+	// Note that currently we cannot nil out check inside typ.under(), because
+	// it's possible that typ is expanded multiple times.
+	//
+	// TODO(rFindley): clean this up so that under is the only function mutating
+	//                 named types.
+	if check != nil {
+		check.later(func() {
+			switch typ.under().(type) {
+			case *Named, *instance:
+				panic("internal error: unexpanded underlying type")
+			}
+			typ.check = nil
+		})
+	}
+	return typ
+}
+
+// Obj returns the type name for the named type t.
+func (t *Named) Obj() *TypeName { return t.obj }
+
+// _Orig returns the original generic type an instantiated type is derived from.
+// If t is not an instantiated type, the result is t.
+func (t *Named) _Orig() *Named { return t.orig }
+
+// TODO(gri) Come up with a better representation and API to distinguish
+//           between parameterized instantiated and non-instantiated types.
+
+// _TParams returns the type parameters of the named type t, or nil.
+// The result is non-nil for an (originally) parameterized type even if it is instantiated.
+func (t *Named) TParams() []*TypeName { return t.expand().tparams }
+
+// _SetTParams sets the type parameters of the named type t.
+func (t *Named) SetTParams(tparams []*TypeName) { t.expand().tparams = tparams }
+
+// _TArgs returns the type arguments after instantiation of the named type t, or nil if not instantiated.
+func (t *Named) TArgs() []Type { return t.targs }
+
+// SetTArgs sets the type arguments of the named type t.
+func (t *Named) SetTArgs(args []Type) { t.targs = args }
+
+// NumMethods returns the number of explicit methods whose receiver is named type t.
+func (t *Named) NumMethods() int { return len(t.expand().methods) }
+
+// Method returns the i'th method of named type t for 0 <= i < t.NumMethods().
+func (t *Named) Method(i int) *Func { return t.expand().methods[i] }
+
+// SetUnderlying sets the underlying type and marks t as complete.
+func (t *Named) SetUnderlying(underlying Type) {
+	if underlying == nil {
+		panic("types.Named.SetUnderlying: underlying type must not be nil")
+	}
+	if _, ok := underlying.(*Named); ok {
+		panic("types.Named.SetUnderlying: underlying type must not be *Named")
+	}
+	t.expand().underlying = underlying
+}
+
+// AddMethod adds method m unless it is already in the method list.
+func (t *Named) AddMethod(m *Func) {
+	t.expand()
+	if i, _ := lookupMethod(t.methods, m.pkg, m.name); i < 0 {
+		t.methods = append(t.methods, m)
+	}
+}
+
+func (t *Named) Underlying() Type { return t.expand().underlying }
+func (t *Named) String() string   { return TypeString(t, nil) }

src/go/types/pointer.go

@@ -0,0 +1,19 @@
+// 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
+
+// A Pointer represents a pointer type.
+type Pointer struct {
+	base Type // element type
+}
+
+// NewPointer returns a new pointer type for the given element (base) type.
+func NewPointer(elem Type) *Pointer { return &Pointer{base: elem} }
+
+// Elem returns the element type for the given pointer p.
+func (p *Pointer) Elem() Type { return p.base }
+
+func (t *Pointer) Underlying() Type { return t }
+func (t *Pointer) String() string   { return TypeString(t, nil) }

src/go/types/slice.go

@@ -0,0 +1,19 @@
+// 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
+
+// A Slice represents a slice type.
+type Slice struct {
+	elem Type
+}
+
+// NewSlice returns a new slice type for the given element type.
+func NewSlice(elem Type) *Slice { return &Slice{elem: elem} }
+
+// Elem returns the element type of slice s.
+func (s *Slice) Elem() Type { return s.elem }
+
+func (t *Slice) Underlying() Type { return t }
+func (t *Slice) String() string   { return TypeString(t, nil) }

src/go/types/tuple.go

@@ -0,0 +1,36 @@
+// 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
+
+// A Tuple represents an ordered list of variables; a nil *Tuple is a valid (empty) tuple.
+// Tuples are used as components of signatures and to represent the type of multiple
+// assignments; they are not first class types of Go.
+type Tuple struct {
+	vars []*Var
+}
+
+// NewTuple returns a new tuple for the given variables.
+func NewTuple(x ...*Var) *Tuple {
+	if len(x) > 0 {
+		return &Tuple{vars: x}
+	}
+	// TODO(gri) Don't represent empty tuples with a (*Tuple)(nil) pointer;
+	//           it's too subtle and causes problems.
+	return nil
+}
+
+// Len returns the number variables of tuple t.
+func (t *Tuple) Len() int {
+	if t != nil {
+		return len(t.vars)
+	}
+	return 0
+}
+
+// At returns the i'th variable of tuple t.
+func (t *Tuple) At(i int) *Var { return t.vars[i] }
+
+func (t *Tuple) Underlying() Type { return t }
+func (t *Tuple) String() string   { return TypeString(t, nil) }

src/go/types/type.go

@@ -4,12 +4,6 @@
 
 package types
 
-import (
-	"go/token"
-	"sync"
-	"sync/atomic"
-)
-
 // A Type represents a type of Go.
 // All types implement the Type interface.
 type Type interface {
@@ -22,379 +16,31 @@ type Type interface {
 	String() string
 }
 
-// BasicKind describes the kind of basic type.
+// top represents the top of the type lattice.
-type BasicKind int
+// It is the underlying type of a type parameter that
+// can be satisfied by any type (ignoring methods),
+// because its type constraint contains no restrictions
+// besides methods.
+type top struct{}
 
-const (
+// theTop is the singleton top type.
-	Invalid BasicKind = iota // type is invalid
+var theTop = &top{}
 
-	// predeclared types
+func (t *top) Underlying() Type { return t }
-	Bool
+func (t *top) String() string   { return TypeString(t, nil) }
-	Int
-	Int8
-	Int16
-	Int32
-	Int64
-	Uint
-	Uint8
-	Uint16
-	Uint32
-	Uint64
-	Uintptr
-	Float32
-	Float64
-	Complex64
-	Complex128
-	String
-	UnsafePointer
 
-	// types for untyped values
+// under returns the true expanded underlying type.
-	UntypedBool
+// If it doesn't exist, the result is Typ[Invalid].
-	UntypedInt
+// under must only be called when a type is known
-	UntypedRune
+// to be fully set up.
-	UntypedFloat
+func under(t Type) Type {
-	UntypedComplex
+	// TODO(gri) is this correct for *Union?
-	UntypedString
+	if n := asNamed(t); n != nil {
-	UntypedNil
+		return n.under()
-
-	// aliases
-	Byte = Uint8
-	Rune = Int32
-)
-
-// BasicInfo is a set of flags describing properties of a basic type.
-type BasicInfo int
-
-// Properties of basic types.
-const (
-	IsBoolean BasicInfo = 1 << iota
-	IsInteger
-	IsUnsigned
-	IsFloat
-	IsComplex
-	IsString
-	IsUntyped
-
-	IsOrdered   = IsInteger | IsFloat | IsString
-	IsNumeric   = IsInteger | IsFloat | IsComplex
-	IsConstType = IsBoolean | IsNumeric | IsString
-)
-
-// A Basic represents a basic type.
-type Basic struct {
-	kind BasicKind
-	info BasicInfo
-	name string
 	}
-
-// Kind returns the kind of basic type b.
-func (b *Basic) Kind() BasicKind { return b.kind }
-
-// Info returns information about properties of basic type b.
-func (b *Basic) Info() BasicInfo { return b.info }
-
-// Name returns the name of basic type b.
-func (b *Basic) Name() string { return b.name }
-
-// An Array represents an array type.
-type Array struct {
-	len  int64
-	elem Type
-}
-
-// NewArray returns a new array type for the given element type and length.
-// A negative length indicates an unknown length.
-func NewArray(elem Type, len int64) *Array { return &Array{len: len, elem: elem} }
-
-// Len returns the length of array a.
-// A negative result indicates an unknown length.
-func (a *Array) Len() int64 { return a.len }
-
-// Elem returns element type of array a.
-func (a *Array) Elem() Type { return a.elem }
-
-// A Slice represents a slice type.
-type Slice struct {
-	elem Type
-}
-
-// NewSlice returns a new slice type for the given element type.
-func NewSlice(elem Type) *Slice { return &Slice{elem: elem} }
-
-// Elem returns the element type of slice s.
-func (s *Slice) Elem() Type { return s.elem }
-
-// A Pointer represents a pointer type.
-type Pointer struct {
-	base Type // element type
-}
-
-// NewPointer returns a new pointer type for the given element (base) type.
-func NewPointer(elem Type) *Pointer { return &Pointer{base: elem} }
-
-// Elem returns the element type for the given pointer p.
-func (p *Pointer) Elem() Type { return p.base }
-
-// A Tuple represents an ordered list of variables; a nil *Tuple is a valid (empty) tuple.
-// Tuples are used as components of signatures and to represent the type of multiple
-// assignments; they are not first class types of Go.
-type Tuple struct {
-	vars []*Var
-}
-
-// NewTuple returns a new tuple for the given variables.
-func NewTuple(x ...*Var) *Tuple {
-	if len(x) > 0 {
-		return &Tuple{vars: x}
-	}
-	// TODO(gri) Don't represent empty tuples with a (*Tuple)(nil) pointer;
-	//           it's too subtle and causes problems.
-	return nil
-}
-
-// Len returns the number variables of tuple t.
-func (t *Tuple) Len() int {
-	if t != nil {
-		return len(t.vars)
-	}
-	return 0
-}
-
-// At returns the i'th variable of tuple t.
-func (t *Tuple) At(i int) *Var { return t.vars[i] }
-
-// A Map represents a map type.
-type Map struct {
-	key, elem Type
-}
-
-// NewMap returns a new map for the given key and element types.
-func NewMap(key, elem Type) *Map {
-	return &Map{key: key, elem: elem}
-}
-
-// Key returns the key type of map m.
-func (m *Map) Key() Type { return m.key }
-
-// Elem returns the element type of map m.
-func (m *Map) Elem() Type { return m.elem }
-
-// A Chan represents a channel type.
-type Chan struct {
-	dir  ChanDir
-	elem Type
-}
-
-// A ChanDir value indicates a channel direction.
-type ChanDir int
-
-// The direction of a channel is indicated by one of these constants.
-const (
-	SendRecv ChanDir = iota
-	SendOnly
-	RecvOnly
-)
-
-// NewChan returns a new channel type for the given direction and element type.
-func NewChan(dir ChanDir, elem Type) *Chan {
-	return &Chan{dir: dir, elem: elem}
-}
-
-// Dir returns the direction of channel c.
-func (c *Chan) Dir() ChanDir { return c.dir }
-
-// Elem returns the element type of channel c.
-func (c *Chan) Elem() Type { return c.elem }
-
-// TODO(rfindley) Clean up Named struct below; specifically the fromRHS field (can we use underlying?).
-
-// A Named represents a named (defined) type.
-type Named struct {
-	check      *Checker    // for Named.under implementation; nilled once under has been called
-	info       typeInfo    // for cycle detection
-	obj        *TypeName   // corresponding declared object
-	orig       *Named      // original, uninstantiated type
-	fromRHS    Type        // type (on RHS of declaration) this *Named type is derived of (for cycle reporting)
-	underlying Type        // possibly a *Named during setup; never a *Named once set up completely
-	tparams    []*TypeName // type parameters, or nil
-	targs      []Type      // type arguments (after instantiation), or nil
-	methods    []*Func     // methods declared for this type (not the method set of this type); signatures are type-checked lazily
-
-	resolve func(*Named) ([]*TypeName, Type, []*Func)
-	once    sync.Once
-}
-
-// NewNamed returns a new named type for the given type name, underlying type, and associated methods.
-// If the given type name obj doesn't have a type yet, its type is set to the returned named type.
-// The underlying type must not be a *Named.
-func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
-	if _, ok := underlying.(*Named); ok {
-		panic("types.NewNamed: underlying type must not be *Named")
-	}
-	return (*Checker)(nil).newNamed(obj, nil, underlying, nil, methods)
-}
-
-func (t *Named) expand() *Named {
-	if t.resolve == nil {
 	return t
 }
 
-	t.once.Do(func() {
-		// TODO(mdempsky): Since we're passing t to resolve anyway
-		// (necessary because types2 expects the receiver type for methods
-		// on defined interface types to be the Named rather than the
-		// underlying Interface), maybe it should just handle calling
-		// SetTParams, SetUnderlying, and AddMethod instead?  Those
-		// methods would need to support reentrant calls though.  It would
-		// also make the API more future-proof towards further extensions
-		// (like SetTParams).
-
-		tparams, underlying, methods := t.resolve(t)
-
-		switch underlying.(type) {
-		case nil, *Named:
-			panic("invalid underlying type")
-		}
-
-		t.tparams = tparams
-		t.underlying = underlying
-		t.methods = methods
-	})
-	return t
-}
-
-func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tparams []*TypeName, methods []*Func) *Named {
-	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, tparams: tparams, methods: methods}
-	if typ.orig == nil {
-		typ.orig = typ
-	}
-	if obj.typ == nil {
-		obj.typ = typ
-	}
-	// Ensure that typ is always expanded, at which point the check field can be
-	// nilled out.
-	//
-	// Note that currently we cannot nil out check inside typ.under(), because
-	// it's possible that typ is expanded multiple times.
-	//
-	// TODO(rFindley): clean this up so that under is the only function mutating
-	//                 named types.
-	if check != nil {
-		check.later(func() {
-			switch typ.under().(type) {
-			case *Named, *instance:
-				panic("internal error: unexpanded underlying type")
-			}
-			typ.check = nil
-		})
-	}
-	return typ
-}
-
-// Obj returns the type name for the named type t.
-func (t *Named) Obj() *TypeName { return t.obj }
-
-// _Orig returns the original generic type an instantiated type is derived from.
-// If t is not an instantiated type, the result is t.
-func (t *Named) _Orig() *Named { return t.orig }
-
-// TODO(gri) Come up with a better representation and API to distinguish
-//           between parameterized instantiated and non-instantiated types.
-
-// _TParams returns the type parameters of the named type t, or nil.
-// The result is non-nil for an (originally) parameterized type even if it is instantiated.
-func (t *Named) TParams() []*TypeName { return t.expand().tparams }
-
-// _SetTParams sets the type parameters of the named type t.
-func (t *Named) SetTParams(tparams []*TypeName) { t.expand().tparams = tparams }
-
-// _TArgs returns the type arguments after instantiation of the named type t, or nil if not instantiated.
-func (t *Named) TArgs() []Type { return t.targs }
-
-// SetTArgs sets the type arguments of the named type t.
-func (t *Named) SetTArgs(args []Type) { t.targs = args }
-
-// NumMethods returns the number of explicit methods whose receiver is named type t.
-func (t *Named) NumMethods() int { return len(t.expand().methods) }
-
-// Method returns the i'th method of named type t for 0 <= i < t.NumMethods().
-func (t *Named) Method(i int) *Func { return t.expand().methods[i] }
-
-// SetUnderlying sets the underlying type and marks t as complete.
-func (t *Named) SetUnderlying(underlying Type) {
-	if underlying == nil {
-		panic("types.Named.SetUnderlying: underlying type must not be nil")
-	}
-	if _, ok := underlying.(*Named); ok {
-		panic("types.Named.SetUnderlying: underlying type must not be *Named")
-	}
-	t.expand().underlying = underlying
-}
-
-// AddMethod adds method m unless it is already in the method list.
-func (t *Named) AddMethod(m *Func) {
-	t.expand()
-	if i, _ := lookupMethod(t.methods, m.pkg, m.name); i < 0 {
-		t.methods = append(t.methods, m)
-	}
-}
-
-// 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      // *Named or *Interface; underlying type is always *Interface
-}
-
-// NewTypeParam returns a new TypeParam.
-func NewTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
-	return (*Checker)(nil).newTypeParam(obj, index, bound)
-}
-
-func (check *Checker) newTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
-	assert(bound != nil)
-
-	// 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: index, bound: bound}
-	if obj.typ == nil {
-		obj.typ = typ
-	}
-	return typ
-}
-
-func (t *TypeParam) Bound() *Interface {
-	// we may not have an interface (error reported elsewhere)
-	iface, _ := under(t.bound).(*Interface)
-	if iface == nil {
-		return &emptyInterface
-	}
-	// use the type bound position if we have one
-	pos := token.NoPos
-	if n, _ := t.bound.(*Named); n != nil {
-		pos = n.obj.pos
-	}
-	// TODO(rFindley) switch this to an unexported method on Checker.
-	computeTypeSet(t.check, pos, iface)
-	return iface
-}
-
 // optype returns a type's operational type. Except for type parameters,
 // the operational type is the same as the underlying type (as returned
 // by under). For Type parameters, the operational type is determined
@@ -424,102 +70,6 @@ func optype(typ Type) Type {
 	return under(typ)
 }
 
-// An instance represents an instantiated generic type syntactically
-// (without expanding the instantiation). Type instances appear only
-// during type-checking and are replaced by their fully instantiated
-// (expanded) types before the end of type-checking.
-type instance struct {
-	check   *Checker    // for lazy instantiation
-	pos     token.Pos   // position of type instantiation; for error reporting only
-	base    *Named      // parameterized type to be instantiated
-	targs   []Type      // type arguments
-	poslist []token.Pos // position of each targ; for error reporting only
-	value   Type        // base(targs...) after instantiation or Typ[Invalid]; nil if not yet set
-}
-
-// expand returns the instantiated (= expanded) type of t.
-// The result is either an instantiated *Named type, or
-// Typ[Invalid] if there was an error.
-func (t *instance) expand() Type {
-	v := t.value
-	if v == nil {
-		v = t.check.instantiate(t.pos, t.base, t.targs, t.poslist)
-		if v == nil {
-			v = Typ[Invalid]
-		}
-		t.value = v
-	}
-	// After instantiation we must have an invalid or a *Named type.
-	if debug && v != Typ[Invalid] {
-		_ = v.(*Named)
-	}
-	return v
-}
-
-// expand expands a type instance into its instantiated
-// type and leaves all other types alone. expand does
-// not recurse.
-func expand(typ Type) Type {
-	if t, _ := typ.(*instance); t != nil {
-		return t.expand()
-	}
-	return typ
-}
-
-// expandf is set to expand.
-// Call expandf when calling expand causes compile-time cycle error.
-var expandf func(Type) Type
-
-func init() { expandf = expand }
-
-// top represents the top of the type lattice.
-// It is the underlying type of a type parameter that
-// can be satisfied by any type (ignoring methods),
-// because its type constraint contains no restrictions
-// besides methods.
-type top struct{}
-
-// theTop is the singleton top type.
-var theTop = &top{}
-
-// Type-specific implementations of Underlying.
-func (t *Basic) Underlying() Type     { return t }
-func (t *Array) Underlying() Type     { return t }
-func (t *Slice) Underlying() Type     { return t }
-func (t *Pointer) Underlying() Type   { return t }
-func (t *Tuple) Underlying() Type     { return t }
-func (t *Map) Underlying() Type       { return t }
-func (t *Chan) Underlying() Type      { return t }
-func (t *Named) Underlying() Type     { return t.expand().underlying }
-func (t *TypeParam) Underlying() Type { return t }
-func (t *instance) Underlying() Type  { return t }
-func (t *top) Underlying() Type       { return t }
-
-// Type-specific implementations of String.
-func (t *Basic) String() string     { return TypeString(t, nil) }
-func (t *Array) String() string     { return TypeString(t, nil) }
-func (t *Slice) String() string     { return TypeString(t, nil) }
-func (t *Pointer) String() string   { return TypeString(t, nil) }
-func (t *Tuple) String() string     { return TypeString(t, nil) }
-func (t *Map) String() string       { return TypeString(t, nil) }
-func (t *Chan) String() string      { return TypeString(t, nil) }
-func (t *Named) String() string     { return TypeString(t, nil) }
-func (t *TypeParam) String() string { return TypeString(t, nil) }
-func (t *instance) String() string  { return TypeString(t, nil) }
-func (t *top) String() string       { return TypeString(t, nil) }
-
-// under returns the true expanded underlying type.
-// If it doesn't exist, the result is Typ[Invalid].
-// under must only be called when a type is known
-// to be fully set up.
-func under(t Type) Type {
-	// TODO(gri) is this correct for *Union?
-	if n := asNamed(t); n != nil {
-		return n.under()
-	}
-	return t
-}
-
 // Converters
 //
 // A converter must only be called when a type is

src/go/types/typeparam.go

@@ -0,0 +1,72 @@
+// 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      // *Named or *Interface; underlying type is always *Interface
+}
+
+// NewTypeParam returns a new TypeParam.
+func NewTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
+	return (*Checker)(nil).newTypeParam(obj, index, bound)
+}
+
+// TODO(rfindley): this is factored slightly differently in types2.
+func (check *Checker) newTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
+	assert(bound != nil)
+
+	// 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: index, bound: bound}
+	if obj.typ == nil {
+		obj.typ = typ
+	}
+	return typ
+}
+
+// TODO(rfindley): types2 to has Index and SetID. Should we add them here?
+
+func (t *TypeParam) Bound() *Interface {
+	// we may not have an interface (error reported elsewhere)
+	iface, _ := under(t.bound).(*Interface)
+	if iface == nil {
+		return &emptyInterface
+	}
+	// use the type bound position if we have one
+	pos := token.NoPos
+	if n, _ := t.bound.(*Named); n != nil {
+		pos = n.obj.pos
+	}
+	// TODO(rFindley) switch this to an unexported method on Checker.
+	computeTypeSet(t.check, pos, iface)
+	return iface
+}
+
+func (t *TypeParam) Underlying() Type { return t }
+func (t *TypeParam) String() string   { return TypeString(t, nil) }