[gostls13.git] / src / cmd / compile / internal / types / type.go

// Copyright 2017 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 (
        "cmd/compile/internal/base"
        "cmd/internal/src"
        "fmt"
        "internal/types/errors"
        "sync"
)

// Object represents an ir.Node, but without needing to import cmd/compile/internal/ir,
// which would cause an import cycle. The uses in other packages must type assert
// values of type Object to ir.Node or a more specific type.
type Object interface {
        Pos() src.XPos
        Sym() *Sym
        Type() *Type
}

//go:generate stringer -type Kind -trimprefix T type.go

// Kind describes a kind of type.
type Kind uint8

const (
        Txxx Kind = iota

        TINT8
        TUINT8
        TINT16
        TUINT16
        TINT32
        TUINT32
        TINT64
        TUINT64
        TINT
        TUINT
        TUINTPTR

        TCOMPLEX64
        TCOMPLEX128

        TFLOAT32
        TFLOAT64

        TBOOL

        TPTR
        TFUNC
        TSLICE
        TARRAY
        TSTRUCT
        TCHAN
        TMAP
        TINTER
        TFORW
        TANY
        TSTRING
        TUNSAFEPTR

        // pseudo-types for literals
        TIDEAL // untyped numeric constants
        TNIL
        TBLANK

        // pseudo-types used temporarily only during frame layout (CalcSize())
        TFUNCARGS
        TCHANARGS

        // SSA backend types
        TSSA     // internal types used by SSA backend (flags, memory, etc.)
        TTUPLE   // a pair of types, used by SSA backend
        TRESULTS // multiple types; the result of calling a function or method, with a memory at the end.

        NTYPE
)

// ChanDir is whether a channel can send, receive, or both.
type ChanDir uint8

func (c ChanDir) CanRecv() bool { return c&Crecv != 0 }
func (c ChanDir) CanSend() bool { return c&Csend != 0 }

const (
        // types of channel
        // must match ../../../../reflect/type.go:/ChanDir
        Crecv ChanDir = 1 << 0
        Csend ChanDir = 1 << 1
        Cboth ChanDir = Crecv | Csend
)

// Types stores pointers to predeclared named types.
//
// It also stores pointers to several special types:
//   - Types[TANY] is the placeholder "any" type recognized by SubstArgTypes.
//   - Types[TBLANK] represents the blank variable's type.
//   - Types[TINTER] is the canonical "interface{}" type.
//   - Types[TNIL] represents the predeclared "nil" value's type.
//   - Types[TUNSAFEPTR] is package unsafe's Pointer type.
var Types [NTYPE]*Type

var (
        // Predeclared alias types. These are actually created as distinct
        // defined types for better error messages, but are then specially
        // treated as identical to their respective underlying types.
        AnyType  *Type
        ByteType *Type
        RuneType *Type

        // Predeclared error interface type.
        ErrorType *Type
        // Predeclared comparable interface type.
        ComparableType *Type

        // Types to represent untyped string and boolean constants.
        UntypedString = newType(TSTRING)
        UntypedBool   = newType(TBOOL)

        // Types to represent untyped numeric constants.
        UntypedInt     = newType(TIDEAL)
        UntypedRune    = newType(TIDEAL)
        UntypedFloat   = newType(TIDEAL)
        UntypedComplex = newType(TIDEAL)
)

// A Type represents a Go type.
//
// There may be multiple unnamed types with identical structure. However, there must
// be a unique Type object for each unique named (defined) type. After noding, a
// package-level type can be looked up by building its unique symbol sym (sym =
// package.Lookup(name)) and checking sym.Def. If sym.Def is non-nil, the type
// already exists at package scope and is available at sym.Def.(*ir.Name).Type().
// Local types (which may have the same name as a package-level type) are
// distinguished by the value of vargen.
type Type struct {
        // extra contains extra etype-specific fields.
        // As an optimization, those etype-specific structs which contain exactly
        // one pointer-shaped field are stored as values rather than pointers when possible.
        //
        // TMAP: *Map
        // TFORW: *Forward
        // TFUNC: *Func
        // TSTRUCT: *Struct
        // TINTER: *Interface
        // TFUNCARGS: FuncArgs
        // TCHANARGS: ChanArgs
        // TCHAN: *Chan
        // TPTR: Ptr
        // TARRAY: *Array
        // TSLICE: Slice
        // TSSA: string
        extra interface{}

        // width is the width of this Type in bytes.
        width int64 // valid if Align > 0

        // list of base methods (excluding embedding)
        methods fields
        // list of all methods (including embedding)
        allMethods fields

        // canonical OTYPE node for a named type (should be an ir.Name node with same sym)
        obj Object
        // the underlying type (type literal or predeclared type) for a defined type
        underlying *Type

        // Cache of composite types, with this type being the element type.
        cache struct {
                ptr   *Type // *T, or nil
                slice *Type // []T, or nil
        }

        vargen int32 // unique name for OTYPE/ONAME

        kind  Kind  // kind of type
        align uint8 // the required alignment of this type, in bytes (0 means Width and Align have not yet been computed)

        flags bitset8

        // For defined (named) generic types, a pointer to the list of type params
        // (in order) of this type that need to be instantiated. For instantiated
        // generic types, this is the targs used to instantiate them. These targs
        // may be typeparams (for re-instantiated types such as Value[T2]) or
        // concrete types (for fully instantiated types such as Value[int]).
        // rparams is only set for named types that are generic or are fully
        // instantiated from a generic type, and is otherwise set to nil.
        // TODO(danscales): choose a better name.
        rparams *[]*Type
}

func (*Type) CanBeAnSSAAux() {}

const (
        typeNotInHeap  = 1 << iota // type cannot be heap allocated
        typeNoalg                  // suppress hash and eq algorithm generation
        typeDeferwidth             // width computation has been deferred and type is on deferredTypeStack
        typeRecur
        typeIsShape  // represents a set of closely related types, for generics
        typeHasShape // there is a shape somewhere in the type
)

func (t *Type) NotInHeap() bool  { return t.flags&typeNotInHeap != 0 }
func (t *Type) Noalg() bool      { return t.flags&typeNoalg != 0 }
func (t *Type) Deferwidth() bool { return t.flags&typeDeferwidth != 0 }
func (t *Type) Recur() bool      { return t.flags&typeRecur != 0 }
func (t *Type) IsShape() bool    { return t.flags&typeIsShape != 0 }
func (t *Type) HasShape() bool   { return t.flags&typeHasShape != 0 }

func (t *Type) SetNotInHeap(b bool)  { t.flags.set(typeNotInHeap, b) }
func (t *Type) SetNoalg(b bool)      { t.flags.set(typeNoalg, b) }
func (t *Type) SetDeferwidth(b bool) { t.flags.set(typeDeferwidth, b) }
func (t *Type) SetRecur(b bool)      { t.flags.set(typeRecur, b) }

// Should always do SetHasShape(true) when doing SetIsShape(true).
func (t *Type) SetIsShape(b bool)  { t.flags.set(typeIsShape, b) }
func (t *Type) SetHasShape(b bool) { t.flags.set(typeHasShape, b) }

// Kind returns the kind of type t.
func (t *Type) Kind() Kind { return t.kind }

// Sym returns the name of type t.
func (t *Type) Sym() *Sym {
        if t.obj != nil {
                return t.obj.Sym()
        }
        return nil
}

// Underlying returns the underlying type of type t.
func (t *Type) Underlying() *Type { return t.underlying }

// Pos returns a position associated with t, if any.
// This should only be used for diagnostics.
func (t *Type) Pos() src.XPos {
        if t.obj != nil {
                return t.obj.Pos()
        }
        return src.NoXPos
}

func (t *Type) RParams() []*Type {
        if t.rparams == nil {
                return nil
        }
        return *t.rparams
}

func (t *Type) SetRParams(rparams []*Type) {
        if len(rparams) == 0 {
                base.Fatalf("Setting nil or zero-length rparams")
        }
        t.rparams = &rparams
        // HasShape should be set if any type argument is or has a shape type.
        for _, rparam := range rparams {
                if rparam.HasShape() {
                        t.SetHasShape(true)
                        break
                }
        }
}

// IsFullyInstantiated reports whether t is a fully instantiated generic type; i.e. an
// instantiated generic type where all type arguments are non-generic or fully
// instantiated generic types.
func (t *Type) IsFullyInstantiated() bool {
        return len(t.RParams()) > 0
}

// Map contains Type fields specific to maps.
type Map struct {
        Key  *Type // Key type
        Elem *Type // Val (elem) type

        Bucket *Type // internal struct type representing a hash bucket
}

// MapType returns t's extra map-specific fields.
func (t *Type) MapType() *Map {
        t.wantEtype(TMAP)
        return t.extra.(*Map)
}

// Forward contains Type fields specific to forward types.
type Forward struct {
        Copyto      []*Type  // where to copy the eventual value to
        Embedlineno src.XPos // first use of this type as an embedded type
}

// forwardType returns t's extra forward-type-specific fields.
func (t *Type) forwardType() *Forward {
        t.wantEtype(TFORW)
        return t.extra.(*Forward)
}

// Func contains Type fields specific to func types.
type Func struct {
        Receiver *Type // function receiver
        Results  *Type // function results
        Params   *Type // function params

        // Argwid is the total width of the function receiver, params, and results.
        // It gets calculated via a temporary TFUNCARGS type.
        // Note that TFUNC's Width is Widthptr.
        Argwid int64
}

// funcType returns t's extra func-specific fields.
func (t *Type) funcType() *Func {
        t.wantEtype(TFUNC)
        return t.extra.(*Func)
}

// StructType contains Type fields specific to struct types.
type Struct struct {
        fields fields

        // Maps have three associated internal structs (see struct MapType).
        // Map links such structs back to their map type.
        Map *Type

        Funarg Funarg // type of function arguments for arg struct
}

// Funarg records the kind of function argument
type Funarg uint8

const (
        FunargNone    Funarg = iota
        FunargRcvr           // receiver
        FunargParams         // input parameters
        FunargResults        // output results
        FunargTparams        // type params
)

// StructType returns t's extra struct-specific fields.
func (t *Type) StructType() *Struct {
        t.wantEtype(TSTRUCT)
        return t.extra.(*Struct)
}

// Interface contains Type fields specific to interface types.
type Interface struct {
}

// Ptr contains Type fields specific to pointer types.
type Ptr struct {
        Elem *Type // element type
}

// ChanArgs contains Type fields specific to TCHANARGS types.
type ChanArgs struct {
        T *Type // reference to a chan type whose elements need a width check
}

// // FuncArgs contains Type fields specific to TFUNCARGS types.
type FuncArgs struct {
        T *Type // reference to a func type whose elements need a width check
}

// Chan contains Type fields specific to channel types.
type Chan struct {
        Elem *Type   // element type
        Dir  ChanDir // channel direction
}

// chanType returns t's extra channel-specific fields.
func (t *Type) chanType() *Chan {
        t.wantEtype(TCHAN)
        return t.extra.(*Chan)
}

type Tuple struct {
        first  *Type
        second *Type
        // Any tuple with a memory type must put that memory type second.
}

// Results are the output from calls that will be late-expanded.
type Results struct {
        Types []*Type // Last element is memory output from call.
}

// Array contains Type fields specific to array types.
type Array struct {
        Elem  *Type // element type
        Bound int64 // number of elements; <0 if unknown yet
}

// Slice contains Type fields specific to slice types.
type Slice struct {
        Elem *Type // element type
}

// A Field is a (Sym, Type) pairing along with some other information, and,
// depending on the context, is used to represent:
//   - a field in a struct
//   - a method in an interface or associated with a named type
//   - a function parameter
type Field struct {
        flags bitset8

        Embedded uint8 // embedded field

        Pos src.XPos

        // Name of field/method/parameter. Can be nil for interface fields embedded
        // in interfaces and unnamed parameters.
        Sym  *Sym
        Type *Type  // field type
        Note string // literal string annotation

        // For fields that represent function parameters, Nname points to the
        // associated ONAME Node. For fields that represent methods, Nname points to
        // the function name node.
        Nname Object

        // Offset in bytes of this field or method within its enclosing struct
        // or interface Type.  Exception: if field is function receiver, arg or
        // result, then this is BOGUS_FUNARG_OFFSET; types does not know the Abi.
        Offset int64
}

const (
        fieldIsDDD = 1 << iota // field is ... argument
        fieldNointerface
)

func (f *Field) IsDDD() bool       { return f.flags&fieldIsDDD != 0 }
func (f *Field) Nointerface() bool { return f.flags&fieldNointerface != 0 }

func (f *Field) SetIsDDD(b bool)       { f.flags.set(fieldIsDDD, b) }
func (f *Field) SetNointerface(b bool) { f.flags.set(fieldNointerface, b) }

// End returns the offset of the first byte immediately after this field.
func (f *Field) End() int64 {
        return f.Offset + f.Type.width
}

// IsMethod reports whether f represents a method rather than a struct field.
func (f *Field) IsMethod() bool {
        return f.Type.kind == TFUNC && f.Type.Recv() != nil
}

// fields is a pointer to a slice of *Field.
// This saves space in Types that do not have fields or methods
// compared to a simple slice of *Field.
type fields struct {
        s *[]*Field
}

// Slice returns the entries in f as a slice.
// Changes to the slice entries will be reflected in f.
func (f *fields) Slice() []*Field {
        if f.s == nil {
                return nil
        }
        return *f.s
}

// Set sets f to a slice.
// This takes ownership of the slice.
func (f *fields) Set(s []*Field) {
        if len(s) == 0 {
                f.s = nil
        } else {
                // Copy s and take address of t rather than s to avoid
                // allocation in the case where len(s) == 0.
                t := s
                f.s = &t
        }
}

// newType returns a new Type of the specified kind.
func newType(et Kind) *Type {
        t := &Type{
                kind:  et,
                width: BADWIDTH,
        }
        t.underlying = t
        // TODO(josharian): lazily initialize some of these?
        switch t.kind {
        case TMAP:
                t.extra = new(Map)
        case TFORW:
                t.extra = new(Forward)
        case TFUNC:
                t.extra = new(Func)
        case TSTRUCT:
                t.extra = new(Struct)
        case TINTER:
                t.extra = new(Interface)
        case TPTR:
                t.extra = Ptr{}
        case TCHANARGS:
                t.extra = ChanArgs{}
        case TFUNCARGS:
                t.extra = FuncArgs{}
        case TCHAN:
                t.extra = new(Chan)
        case TTUPLE:
                t.extra = new(Tuple)
        case TRESULTS:
                t.extra = new(Results)
        }
        return t
}

// NewArray returns a new fixed-length array Type.
func NewArray(elem *Type, bound int64) *Type {
        if bound < 0 {
                base.Fatalf("NewArray: invalid bound %v", bound)
        }
        t := newType(TARRAY)
        t.extra = &Array{Elem: elem, Bound: bound}
        if elem.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

// NewSlice returns the slice Type with element type elem.
func NewSlice(elem *Type) *Type {
        if t := elem.cache.slice; t != nil {
                if t.Elem() != elem {
                        base.Fatalf("elem mismatch")
                }
                if elem.HasShape() != t.HasShape() {
                        base.Fatalf("Incorrect HasShape flag for cached slice type")
                }
                return t
        }

        t := newType(TSLICE)
        t.extra = Slice{Elem: elem}
        elem.cache.slice = t
        if elem.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

// NewChan returns a new chan Type with direction dir.
func NewChan(elem *Type, dir ChanDir) *Type {
        t := newType(TCHAN)
        ct := t.chanType()
        ct.Elem = elem
        ct.Dir = dir
        if elem.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

func NewTuple(t1, t2 *Type) *Type {
        t := newType(TTUPLE)
        t.extra.(*Tuple).first = t1
        t.extra.(*Tuple).second = t2
        if t1.HasShape() || t2.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

func newResults(types []*Type) *Type {
        t := newType(TRESULTS)
        t.extra.(*Results).Types = types
        return t
}

func NewResults(types []*Type) *Type {
        if len(types) == 1 && types[0] == TypeMem {
                return TypeResultMem
        }
        return newResults(types)
}

func newSSA(name string) *Type {
        t := newType(TSSA)
        t.extra = name
        return t
}

// NewMap returns a new map Type with key type k and element (aka value) type v.
func NewMap(k, v *Type) *Type {
        t := newType(TMAP)
        mt := t.MapType()
        mt.Key = k
        mt.Elem = v
        if k.HasShape() || v.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

// NewPtrCacheEnabled controls whether *T Types are cached in T.
// Caching is disabled just before starting the backend.
// This allows the backend to run concurrently.
var NewPtrCacheEnabled = true

// NewPtr returns the pointer type pointing to t.
func NewPtr(elem *Type) *Type {
        if elem == nil {
                base.Fatalf("NewPtr: pointer to elem Type is nil")
        }

        if t := elem.cache.ptr; t != nil {
                if t.Elem() != elem {
                        base.Fatalf("NewPtr: elem mismatch")
                }
                if elem.HasShape() != t.HasShape() {
                        base.Fatalf("Incorrect HasShape flag for cached pointer type")
                }
                return t
        }

        t := newType(TPTR)
        t.extra = Ptr{Elem: elem}
        t.width = int64(PtrSize)
        t.align = uint8(PtrSize)
        if NewPtrCacheEnabled {
                elem.cache.ptr = t
        }
        if elem.HasShape() {
                t.SetHasShape(true)
        }
        return t
}

// NewChanArgs returns a new TCHANARGS type for channel type c.
func NewChanArgs(c *Type) *Type {
        t := newType(TCHANARGS)
        t.extra = ChanArgs{T: c}
        return t
}

// NewFuncArgs returns a new TFUNCARGS type for func type f.
func NewFuncArgs(f *Type) *Type {
        t := newType(TFUNCARGS)
        t.extra = FuncArgs{T: f}
        return t
}

func NewField(pos src.XPos, sym *Sym, typ *Type) *Field {
        f := &Field{
                Pos:    pos,
                Sym:    sym,
                Type:   typ,
                Offset: BADWIDTH,
        }
        if typ == nil {
                base.Fatalf("typ is nil")
        }
        return f
}

// SubstAny walks t, replacing instances of "any" with successive
// elements removed from types.  It returns the substituted type.
func SubstAny(t *Type, types *[]*Type) *Type {
        if t == nil {
                return nil
        }

        switch t.kind {
        default:
                // Leave the type unchanged.

        case TANY:
                if len(*types) == 0 {
                        base.Fatalf("SubstArgTypes: not enough argument types")
                }
                t = (*types)[0]
                *types = (*types)[1:]

        case TPTR:
                elem := SubstAny(t.Elem(), types)
                if elem != t.Elem() {
                        t = t.copy()
                        t.extra = Ptr{Elem: elem}
                }

        case TARRAY:
                elem := SubstAny(t.Elem(), types)
                if elem != t.Elem() {
                        t = t.copy()
                        t.extra.(*Array).Elem = elem
                }

        case TSLICE:
                elem := SubstAny(t.Elem(), types)
                if elem != t.Elem() {
                        t = t.copy()
                        t.extra = Slice{Elem: elem}
                }

        case TCHAN:
                elem := SubstAny(t.Elem(), types)
                if elem != t.Elem() {
                        t = t.copy()
                        t.extra.(*Chan).Elem = elem
                }

        case TMAP:
                key := SubstAny(t.Key(), types)
                elem := SubstAny(t.Elem(), types)
                if key != t.Key() || elem != t.Elem() {
                        t = t.copy()
                        t.extra.(*Map).Key = key
                        t.extra.(*Map).Elem = elem
                }

        case TFUNC:
                recvs := SubstAny(t.recvsTuple(), types)
                params := SubstAny(t.paramsTuple(), types)
                results := SubstAny(t.ResultsTuple(), types)
                if recvs != t.recvsTuple() || params != t.paramsTuple() || results != t.ResultsTuple() {
                        t = t.copy()
                        t.funcType().Receiver = recvs
                        t.funcType().Results = results
                        t.funcType().Params = params
                }

        case TSTRUCT:
                // Make a copy of all fields, including ones whose type does not change.
                // This prevents aliasing across functions, which can lead to later
                // fields getting their Offset incorrectly overwritten.
                fields := t.Fields()
                nfs := make([]*Field, len(fields))
                for i, f := range fields {
                        nft := SubstAny(f.Type, types)
                        nfs[i] = f.Copy()
                        nfs[i].Type = nft
                }
                t = t.copy()
                t.setFields(nfs)
        }

        return t
}

// copy returns a shallow copy of the Type.
func (t *Type) copy() *Type {
        if t == nil {
                return nil
        }
        nt := *t
        // copy any *T Extra fields, to avoid aliasing
        switch t.kind {
        case TMAP:
                x := *t.extra.(*Map)
                nt.extra = &x
        case TFORW:
                x := *t.extra.(*Forward)
                nt.extra = &x
        case TFUNC:
                x := *t.extra.(*Func)
                nt.extra = &x
        case TSTRUCT:
                x := *t.extra.(*Struct)
                nt.extra = &x
        case TINTER:
                x := *t.extra.(*Interface)
                nt.extra = &x
        case TCHAN:
                x := *t.extra.(*Chan)
                nt.extra = &x
        case TARRAY:
                x := *t.extra.(*Array)
                nt.extra = &x
        case TTUPLE, TSSA, TRESULTS:
                base.Fatalf("ssa types cannot be copied")
        }
        // TODO(mdempsky): Find out why this is necessary and explain.
        if t.underlying == t {
                nt.underlying = &nt
        }
        return &nt
}

func (f *Field) Copy() *Field {
        nf := *f
        return &nf
}

func (t *Type) wantEtype(et Kind) {
        if t.kind != et {
                base.Fatalf("want %v, but have %v", et, t)
        }
}

func (t *Type) recvsTuple() *Type  { return t.funcType().Receiver }
func (t *Type) paramsTuple() *Type { return t.funcType().Params }

// ResultTuple returns the result type of signature type t as a tuple.
// This can be used as the type of multi-valued call expressions.
func (t *Type) ResultsTuple() *Type { return t.funcType().Results }

// Recvs returns a slice of receiver parameters of signature type t.
// The returned slice always has length 0 or 1.
func (t *Type) Recvs() []*Field { return t.funcType().Receiver.Fields() }

// Params returns a slice of regular parameters of signature type t.
func (t *Type) Params() []*Field { return t.funcType().Params.Fields() }

// Results returns a slice of result parameters of signature type t.
func (t *Type) Results() []*Field { return t.funcType().Results.Fields() }

func (t *Type) NumRecvs() int   { return t.funcType().Receiver.NumFields() }
func (t *Type) NumParams() int  { return t.funcType().Params.NumFields() }
func (t *Type) NumResults() int { return t.funcType().Results.NumFields() }

// IsVariadic reports whether function type t is variadic.
func (t *Type) IsVariadic() bool {
        n := t.NumParams()
        return n > 0 && t.Param(n-1).IsDDD()
}

// Recv returns the receiver of function type t, if any.
func (t *Type) Recv() *Field {
        s := t.recvsTuple()
        if s.NumFields() == 0 {
                return nil
        }
        return s.Field(0)
}

// Param returns the i'th parameter of signature type t.
func (t *Type) Param(i int) *Field { return t.Params()[i] }

// Result returns the i'th result of signature type t.
func (t *Type) Result(i int) *Field { return t.Results()[i] }

// RecvsParamsResults stores the accessor functions for a function Type's
// receiver, parameters, and result parameters, in that order.
// It can be used to iterate over all of a function's parameter lists.
var RecvsParamsResults = [3]func(*Type) []*Field{
        (*Type).Recvs, (*Type).Params, (*Type).Results,
}

// RecvsParams is like RecvsParamsResults, but omits result parameters.
var RecvsParams = [2]func(*Type) []*Field{
        (*Type).Recvs, (*Type).Params,
}

// ParamsResults is like RecvsParamsResults, but omits receiver parameters.
var ParamsResults = [2]func(*Type) []*Field{
        (*Type).Params, (*Type).Results,
}

// Key returns the key type of map type t.
func (t *Type) Key() *Type {
        t.wantEtype(TMAP)
        return t.extra.(*Map).Key
}

// Elem returns the type of elements of t.
// Usable with pointers, channels, arrays, slices, and maps.
func (t *Type) Elem() *Type {
        switch t.kind {
        case TPTR:
                return t.extra.(Ptr).Elem
        case TARRAY:
                return t.extra.(*Array).Elem
        case TSLICE:
                return t.extra.(Slice).Elem
        case TCHAN:
                return t.extra.(*Chan).Elem
        case TMAP:
                return t.extra.(*Map).Elem
        }
        base.Fatalf("Type.Elem %s", t.kind)
        return nil
}

// ChanArgs returns the channel type for TCHANARGS type t.
func (t *Type) ChanArgs() *Type {
        t.wantEtype(TCHANARGS)
        return t.extra.(ChanArgs).T
}

// FuncArgs returns the func type for TFUNCARGS type t.
func (t *Type) FuncArgs() *Type {
        t.wantEtype(TFUNCARGS)
        return t.extra.(FuncArgs).T
}

// IsFuncArgStruct reports whether t is a struct representing function parameters or results.
func (t *Type) IsFuncArgStruct() bool {
        return t.kind == TSTRUCT && t.extra.(*Struct).Funarg != FunargNone
}

// Methods returns a pointer to the base methods (excluding embedding) for type t.
// These can either be concrete methods (for non-interface types) or interface
// methods (for interface types).
func (t *Type) Methods() []*Field {
        return t.methods.Slice()
}

// AllMethods returns a pointer to all the methods (including embedding) for type t.
// For an interface type, this is the set of methods that are typically iterated
// over. For non-interface types, AllMethods() only returns a valid result after
// CalcMethods() has been called at least once.
func (t *Type) AllMethods() []*Field {
        if t.kind == TINTER {
                // Calculate the full method set of an interface type on the fly
                // now, if not done yet.
                CalcSize(t)
        }
        return t.allMethods.Slice()
}

// SetMethods sets the direct method set for type t (i.e., *not*
// including promoted methods from embedded types).
func (t *Type) SetMethods(fs []*Field) {
        t.methods.Set(fs)
}

// SetAllMethods sets the set of all methods for type t (i.e.,
// including promoted methods from embedded types).
func (t *Type) SetAllMethods(fs []*Field) {
        t.allMethods.Set(fs)
}

// fields returns the fields of struct type t.
func (t *Type) fields() *fields {
        t.wantEtype(TSTRUCT)
        return &t.extra.(*Struct).fields
}

// Field returns the i'th field of struct type t.
func (t *Type) Field(i int) *Field { return t.Fields()[i] }

// Fields returns a slice of containing all fields of
// a struct type t.
func (t *Type) Fields() []*Field { return t.fields().Slice() }

// setFields sets struct type t's fields to fields.
func (t *Type) setFields(fields []*Field) {
        // If we've calculated the width of t before,
        // then some other type such as a function signature
        // might now have the wrong type.
        // Rather than try to track and invalidate those,
        // enforce that SetFields cannot be called once
        // t's width has been calculated.
        if t.widthCalculated() {
                base.Fatalf("SetFields of %v: width previously calculated", t)
        }
        t.wantEtype(TSTRUCT)
        t.fields().Set(fields)
}

// SetInterface sets the base methods of an interface type t.
func (t *Type) SetInterface(methods []*Field) {
        t.wantEtype(TINTER)
        t.methods.Set(methods)
}

// ArgWidth returns the total aligned argument size for a function.
// It includes the receiver, parameters, and results.
func (t *Type) ArgWidth() int64 {
        t.wantEtype(TFUNC)
        return t.extra.(*Func).Argwid
}

func (t *Type) Size() int64 {
        if t.kind == TSSA {
                if t == TypeInt128 {
                        return 16
                }
                return 0
        }
        CalcSize(t)
        return t.width
}

func (t *Type) Alignment() int64 {
        CalcSize(t)
        return int64(t.align)
}

func (t *Type) SimpleString() string {
        return t.kind.String()
}

// Cmp is a comparison between values a and b.
//
//      -1 if a < b
//       0 if a == b
//       1 if a > b
type Cmp int8

const (
        CMPlt = Cmp(-1)
        CMPeq = Cmp(0)
        CMPgt = Cmp(1)
)

// Compare compares types for purposes of the SSA back
// end, returning a Cmp (one of CMPlt, CMPeq, CMPgt).
// The answers are correct for an optimizer
// or code generator, but not necessarily typechecking.
// The order chosen is arbitrary, only consistency and division
// into equivalence classes (Types that compare CMPeq) matters.
func (t *Type) Compare(x *Type) Cmp {
        if x == t {
                return CMPeq
        }
        return t.cmp(x)
}

func cmpForNe(x bool) Cmp {
        if x {
                return CMPlt
        }
        return CMPgt
}

func (r *Sym) cmpsym(s *Sym) Cmp {
        if r == s {
                return CMPeq
        }
        if r == nil {
                return CMPlt
        }
        if s == nil {
                return CMPgt
        }
        // Fast sort, not pretty sort
        if len(r.Name) != len(s.Name) {
                return cmpForNe(len(r.Name) < len(s.Name))
        }
        if r.Pkg != s.Pkg {
                if len(r.Pkg.Prefix) != len(s.Pkg.Prefix) {
                        return cmpForNe(len(r.Pkg.Prefix) < len(s.Pkg.Prefix))
                }
                if r.Pkg.Prefix != s.Pkg.Prefix {
                        return cmpForNe(r.Pkg.Prefix < s.Pkg.Prefix)
                }
        }
        if r.Name != s.Name {
                return cmpForNe(r.Name < s.Name)
        }
        return CMPeq
}

// cmp compares two *Types t and x, returning CMPlt,
// CMPeq, CMPgt as t<x, t==x, t>x, for an arbitrary
// and optimizer-centric notion of comparison.
// TODO(josharian): make this safe for recursive interface types
// and use in signatlist sorting. See issue 19869.
func (t *Type) cmp(x *Type) Cmp {
        // This follows the structure of function identical in identity.go
        // with two exceptions.
        // 1. Symbols are compared more carefully because a <,=,> result is desired.
        // 2. Maps are treated specially to avoid endless recursion -- maps
        //    contain an internal data type not expressible in Go source code.
        if t == x {
                return CMPeq
        }
        if t == nil {
                return CMPlt
        }
        if x == nil {
                return CMPgt
        }

        if t.kind != x.kind {
                return cmpForNe(t.kind < x.kind)
        }

        if t.obj != nil || x.obj != nil {
                // Special case: we keep byte and uint8 separate
                // for error messages. Treat them as equal.
                switch t.kind {
                case TUINT8:
                        if (t == Types[TUINT8] || t == ByteType) && (x == Types[TUINT8] || x == ByteType) {
                                return CMPeq
                        }

                case TINT32:
                        if (t == Types[RuneType.kind] || t == RuneType) && (x == Types[RuneType.kind] || x == RuneType) {
                                return CMPeq
                        }

                case TINTER:
                        // Make sure named any type matches any empty interface.
                        if t == AnyType && x.IsEmptyInterface() || x == AnyType && t.IsEmptyInterface() {
                                return CMPeq
                        }
                }
        }

        if c := t.Sym().cmpsym(x.Sym()); c != CMPeq {
                return c
        }

        if x.obj != nil {
                // Syms non-nil, if vargens match then equal.
                if t.vargen != x.vargen {
                        return cmpForNe(t.vargen < x.vargen)
                }
                return CMPeq
        }
        // both syms nil, look at structure below.

        switch t.kind {
        case TBOOL, TFLOAT32, TFLOAT64, TCOMPLEX64, TCOMPLEX128, TUNSAFEPTR, TUINTPTR,
                TINT8, TINT16, TINT32, TINT64, TINT, TUINT8, TUINT16, TUINT32, TUINT64, TUINT:
                return CMPeq

        case TSSA:
                tname := t.extra.(string)
                xname := x.extra.(string)
                // desire fast sorting, not pretty sorting.
                if len(tname) == len(xname) {
                        if tname == xname {
                                return CMPeq
                        }
                        if tname < xname {
                                return CMPlt
                        }
                        return CMPgt
                }
                if len(tname) > len(xname) {
                        return CMPgt
                }
                return CMPlt

        case TTUPLE:
                xtup := x.extra.(*Tuple)
                ttup := t.extra.(*Tuple)
                if c := ttup.first.Compare(xtup.first); c != CMPeq {
                        return c
                }
                return ttup.second.Compare(xtup.second)

        case TRESULTS:
                xResults := x.extra.(*Results)
                tResults := t.extra.(*Results)
                xl, tl := len(xResults.Types), len(tResults.Types)
                if tl != xl {
                        if tl < xl {
                                return CMPlt
                        }
                        return CMPgt
                }
                for i := 0; i < tl; i++ {
                        if c := tResults.Types[i].Compare(xResults.Types[i]); c != CMPeq {
                                return c
                        }
                }
                return CMPeq

        case TMAP:
                if c := t.Key().cmp(x.Key()); c != CMPeq {
                        return c
                }
                return t.Elem().cmp(x.Elem())

        case TPTR, TSLICE:
                // No special cases for these, they are handled
                // by the general code after the switch.

        case TSTRUCT:
                if t.StructType().Map == nil {
                        if x.StructType().Map != nil {
                                return CMPlt // nil < non-nil
                        }
                        // to the fallthrough
                } else if x.StructType().Map == nil {
                        return CMPgt // nil > non-nil
                } else if t.StructType().Map.MapType().Bucket == t {
                        // Both have non-nil Map
                        // Special case for Maps which include a recursive type where the recursion is not broken with a named type
                        if x.StructType().Map.MapType().Bucket != x {
                                return CMPlt // bucket maps are least
                        }
                        return t.StructType().Map.cmp(x.StructType().Map)
                } else if x.StructType().Map.MapType().Bucket == x {
                        return CMPgt // bucket maps are least
                } // If t != t.Map.Bucket, fall through to general case

                tfs := t.Fields()
                xfs := x.Fields()
                for i := 0; i < len(tfs) && i < len(xfs); i++ {
                        t1, x1 := tfs[i], xfs[i]
                        if t1.Embedded != x1.Embedded {
                                return cmpForNe(t1.Embedded < x1.Embedded)
                        }
                        if t1.Note != x1.Note {
                                return cmpForNe(t1.Note < x1.Note)
                        }
                        if c := t1.Sym.cmpsym(x1.Sym); c != CMPeq {
                                return c
                        }
                        if c := t1.Type.cmp(x1.Type); c != CMPeq {
                                return c
                        }
                }
                if len(tfs) != len(xfs) {
                        return cmpForNe(len(tfs) < len(xfs))
                }
                return CMPeq

        case TINTER:
                tfs := t.AllMethods()
                xfs := x.AllMethods()
                for i := 0; i < len(tfs) && i < len(xfs); i++ {
                        t1, x1 := tfs[i], xfs[i]
                        if c := t1.Sym.cmpsym(x1.Sym); c != CMPeq {
                                return c
                        }
                        if c := t1.Type.cmp(x1.Type); c != CMPeq {
                                return c
                        }
                }
                if len(tfs) != len(xfs) {
                        return cmpForNe(len(tfs) < len(xfs))
                }
                return CMPeq

        case TFUNC:
                for _, f := range &RecvsParamsResults {
                        // Loop over fields in structs, ignoring argument names.
                        tfs := f(t)
                        xfs := f(x)
                        for i := 0; i < len(tfs) && i < len(xfs); i++ {
                                ta := tfs[i]
                                tb := xfs[i]
                                if ta.IsDDD() != tb.IsDDD() {
                                        return cmpForNe(!ta.IsDDD())
                                }
                                if c := ta.Type.cmp(tb.Type); c != CMPeq {
                                        return c
                                }
                        }
                        if len(tfs) != len(xfs) {
                                return cmpForNe(len(tfs) < len(xfs))
                        }
                }
                return CMPeq

        case TARRAY:
                if t.NumElem() != x.NumElem() {
                        return cmpForNe(t.NumElem() < x.NumElem())
                }

        case TCHAN:
                if t.ChanDir() != x.ChanDir() {
                        return cmpForNe(t.ChanDir() < x.ChanDir())
                }

        default:
                e := fmt.Sprintf("Do not know how to compare %v with %v", t, x)
                panic(e)
        }

        // Common element type comparison for TARRAY, TCHAN, TPTR, and TSLICE.
        return t.Elem().cmp(x.Elem())
}

// IsKind reports whether t is a Type of the specified kind.
func (t *Type) IsKind(et Kind) bool {
        return t != nil && t.kind == et
}

func (t *Type) IsBoolean() bool {
        return t.kind == TBOOL
}

var unsignedEType = [...]Kind{
        TINT8:    TUINT8,
        TUINT8:   TUINT8,
        TINT16:   TUINT16,
        TUINT16:  TUINT16,
        TINT32:   TUINT32,
        TUINT32:  TUINT32,
        TINT64:   TUINT64,
        TUINT64:  TUINT64,
        TINT:     TUINT,
        TUINT:    TUINT,
        TUINTPTR: TUINTPTR,
}

// ToUnsigned returns the unsigned equivalent of integer type t.
func (t *Type) ToUnsigned() *Type {
        if !t.IsInteger() {
                base.Fatalf("unsignedType(%v)", t)
        }
        return Types[unsignedEType[t.kind]]
}

func (t *Type) IsInteger() bool {
        switch t.kind {
        case TINT8, TUINT8, TINT16, TUINT16, TINT32, TUINT32, TINT64, TUINT64, TINT, TUINT, TUINTPTR:
                return true
        }
        return t == UntypedInt || t == UntypedRune
}

func (t *Type) IsSigned() bool {
        switch t.kind {
        case TINT8, TINT16, TINT32, TINT64, TINT:
                return true
        }
        return false
}

func (t *Type) IsUnsigned() bool {
        switch t.kind {
        case TUINT8, TUINT16, TUINT32, TUINT64, TUINT, TUINTPTR:
                return true
        }
        return false
}

func (t *Type) IsFloat() bool {
        return t.kind == TFLOAT32 || t.kind == TFLOAT64 || t == UntypedFloat
}

func (t *Type) IsComplex() bool {
        return t.kind == TCOMPLEX64 || t.kind == TCOMPLEX128 || t == UntypedComplex
}

// IsPtr reports whether t is a regular Go pointer type.
// This does not include unsafe.Pointer.
func (t *Type) IsPtr() bool {
        return t.kind == TPTR
}

// IsPtrElem reports whether t is the element of a pointer (to t).
func (t *Type) IsPtrElem() bool {
        return t.cache.ptr != nil
}

// IsUnsafePtr reports whether t is an unsafe pointer.
func (t *Type) IsUnsafePtr() bool {
        return t.kind == TUNSAFEPTR
}

// IsUintptr reports whether t is a uintptr.
func (t *Type) IsUintptr() bool {
        return t.kind == TUINTPTR
}

// IsPtrShaped reports whether t is represented by a single machine pointer.
// In addition to regular Go pointer types, this includes map, channel, and
// function types and unsafe.Pointer. It does not include array or struct types
// that consist of a single pointer shaped type.
// TODO(mdempsky): Should it? See golang.org/issue/15028.
func (t *Type) IsPtrShaped() bool {
        return t.kind == TPTR || t.kind == TUNSAFEPTR ||
                t.kind == TMAP || t.kind == TCHAN || t.kind == TFUNC
}

// HasNil reports whether the set of values determined by t includes nil.
func (t *Type) HasNil() bool {
        switch t.kind {
        case TCHAN, TFUNC, TINTER, TMAP, TNIL, TPTR, TSLICE, TUNSAFEPTR:
                return true
        }
        return false
}

func (t *Type) IsString() bool {
        return t.kind == TSTRING
}

func (t *Type) IsMap() bool {
        return t.kind == TMAP
}

func (t *Type) IsChan() bool {
        return t.kind == TCHAN
}

func (t *Type) IsSlice() bool {
        return t.kind == TSLICE
}

func (t *Type) IsArray() bool {
        return t.kind == TARRAY
}

func (t *Type) IsStruct() bool {
        return t.kind == TSTRUCT
}

func (t *Type) IsInterface() bool {
        return t.kind == TINTER
}

// IsEmptyInterface reports whether t is an empty interface type.
func (t *Type) IsEmptyInterface() bool {
        return t.IsInterface() && len(t.AllMethods()) == 0
}

// IsScalar reports whether 't' is a scalar Go type, e.g.
// bool/int/float/complex. Note that struct and array types consisting
// of a single scalar element are not considered scalar, likewise
// pointer types are also not considered scalar.
func (t *Type) IsScalar() bool {
        switch t.kind {
        case TBOOL, TINT8, TUINT8, TINT16, TUINT16, TINT32,
                TUINT32, TINT64, TUINT64, TINT, TUINT,
                TUINTPTR, TCOMPLEX64, TCOMPLEX128, TFLOAT32, TFLOAT64:
                return true
        }
        return false
}

func (t *Type) PtrTo() *Type {
        return NewPtr(t)
}

func (t *Type) NumFields() int {
        if t.kind == TRESULTS {
                return len(t.extra.(*Results).Types)
        }
        return len(t.Fields())
}
func (t *Type) FieldType(i int) *Type {
        if t.kind == TTUPLE {
                switch i {
                case 0:
                        return t.extra.(*Tuple).first
                case 1:
                        return t.extra.(*Tuple).second
                default:
                        panic("bad tuple index")
                }
        }
        if t.kind == TRESULTS {
                return t.extra.(*Results).Types[i]
        }
        return t.Field(i).Type
}
func (t *Type) FieldOff(i int) int64 {
        return t.Field(i).Offset
}
func (t *Type) FieldName(i int) string {
        return t.Field(i).Sym.Name
}

func (t *Type) NumElem() int64 {
        t.wantEtype(TARRAY)
        return t.extra.(*Array).Bound
}

type componentsIncludeBlankFields bool

const (
        IgnoreBlankFields componentsIncludeBlankFields = false
        CountBlankFields  componentsIncludeBlankFields = true
)

// NumComponents returns the number of primitive elements that compose t.
// Struct and array types are flattened for the purpose of counting.
// All other types (including string, slice, and interface types) count as one element.
// If countBlank is IgnoreBlankFields, then blank struct fields
// (and their comprised elements) are excluded from the count.
// struct { x, y [3]int } has six components; [10]struct{ x, y string } has twenty.
func (t *Type) NumComponents(countBlank componentsIncludeBlankFields) int64 {
        switch t.kind {
        case TSTRUCT:
                if t.IsFuncArgStruct() {
                        base.Fatalf("NumComponents func arg struct")
                }
                var n int64
                for _, f := range t.Fields() {
                        if countBlank == IgnoreBlankFields && f.Sym.IsBlank() {
                                continue
                        }
                        n += f.Type.NumComponents(countBlank)
                }
                return n
        case TARRAY:
                return t.NumElem() * t.Elem().NumComponents(countBlank)
        }
        return 1
}

// SoleComponent returns the only primitive component in t,
// if there is exactly one. Otherwise, it returns nil.
// Components are counted as in NumComponents, including blank fields.
// Keep in sync with cmd/compile/internal/walk/convert.go:soleComponent.
func (t *Type) SoleComponent() *Type {
        switch t.kind {
        case TSTRUCT:
                if t.IsFuncArgStruct() {
                        base.Fatalf("SoleComponent func arg struct")
                }
                if t.NumFields() != 1 {
                        return nil
                }
                return t.Field(0).Type.SoleComponent()
        case TARRAY:
                if t.NumElem() != 1 {
                        return nil
                }
                return t.Elem().SoleComponent()
        }
        return t
}

// ChanDir returns the direction of a channel type t.
// The direction will be one of Crecv, Csend, or Cboth.
func (t *Type) ChanDir() ChanDir {
        t.wantEtype(TCHAN)
        return t.extra.(*Chan).Dir
}

func (t *Type) IsMemory() bool {
        if t == TypeMem || t.kind == TTUPLE && t.extra.(*Tuple).second == TypeMem {
                return true
        }
        if t.kind == TRESULTS {
                if types := t.extra.(*Results).Types; len(types) > 0 && types[len(types)-1] == TypeMem {
                        return true
                }
        }
        return false
}
func (t *Type) IsFlags() bool   { return t == TypeFlags }
func (t *Type) IsVoid() bool    { return t == TypeVoid }
func (t *Type) IsTuple() bool   { return t.kind == TTUPLE }
func (t *Type) IsResults() bool { return t.kind == TRESULTS }

// IsUntyped reports whether t is an untyped type.
func (t *Type) IsUntyped() bool {
        if t == nil {
                return false
        }
        if t == UntypedString || t == UntypedBool {
                return true
        }
        switch t.kind {
        case TNIL, TIDEAL:
                return true
        }
        return false
}

// HasPointers reports whether t contains a heap pointer.
// Note that this function ignores pointers to not-in-heap types.
func (t *Type) HasPointers() bool {
        return PtrDataSize(t) > 0
}

var recvType *Type

// FakeRecvType returns the singleton type used for interface method receivers.
func FakeRecvType() *Type {
        if recvType == nil {
                recvType = NewPtr(newType(TSTRUCT))
        }
        return recvType
}

func FakeRecv() *Field {
        return NewField(base.AutogeneratedPos, nil, FakeRecvType())
}

var (
        // TSSA types. HasPointers assumes these are pointer-free.
        TypeInvalid   = newSSA("invalid")
        TypeMem       = newSSA("mem")
        TypeFlags     = newSSA("flags")
        TypeVoid      = newSSA("void")
        TypeInt128    = newSSA("int128")
        TypeResultMem = newResults([]*Type{TypeMem})
)

func init() {
        TypeInt128.width = 16
        TypeInt128.align = 8
}

// NewNamed returns a new named type for the given type name. obj should be an
// ir.Name. The new type is incomplete (marked as TFORW kind), and the underlying
// type should be set later via SetUnderlying(). References to the type are
// maintained until the type is filled in, so those references can be updated when
// the type is complete.
func NewNamed(obj Object) *Type {
        t := newType(TFORW)
        t.obj = obj
        if obj.Sym().Pkg == ShapePkg {
                t.SetIsShape(true)
                t.SetHasShape(true)
        }
        return t
}

// Obj returns the canonical type name node for a named type t, nil for an unnamed type.
func (t *Type) Obj() Object {
        return t.obj
}

// typeGen tracks the number of function-scoped defined types that
// have been declared. It's used to generate unique linker symbols for
// their runtime type descriptors.
var typeGen int32

// SetVargen assigns a unique generation number to type t, which must
// be a defined type declared within function scope. The generation
// number is used to distinguish it from other similarly spelled
// defined types from the same package.
//
// TODO(mdempsky): Come up with a better solution.
func (t *Type) SetVargen() {
        base.Assertf(t.Sym() != nil, "SetVargen on anonymous type %v", t)
        base.Assertf(t.vargen == 0, "type %v already has Vargen %v", t, t.vargen)

        typeGen++
        t.vargen = typeGen
}

// SetUnderlying sets the underlying type of an incomplete type (i.e. type whose kind
// is currently TFORW). SetUnderlying automatically updates any types that were waiting
// for this type to be completed.
func (t *Type) SetUnderlying(underlying *Type) {
        if underlying.kind == TFORW {
                // This type isn't computed yet; when it is, update n.
                underlying.forwardType().Copyto = append(underlying.forwardType().Copyto, t)
                return
        }

        ft := t.forwardType()

        // TODO(mdempsky): Fix Type rekinding.
        t.kind = underlying.kind
        t.extra = underlying.extra
        t.width = underlying.width
        t.align = underlying.align
        t.underlying = underlying.underlying

        if underlying.NotInHeap() {
                t.SetNotInHeap(true)
        }
        if underlying.HasShape() {
                t.SetHasShape(true)
        }

        // spec: "The declared type does not inherit any methods bound
        // to the existing type, but the method set of an interface
        // type [...] remains unchanged."
        if t.IsInterface() {
                t.methods = underlying.methods
                t.allMethods = underlying.allMethods
        }

        // Update types waiting on this type.
        for _, w := range ft.Copyto {
                w.SetUnderlying(t)
        }

        // Double-check use of type as embedded type.
        if ft.Embedlineno.IsKnown() {
                if t.IsPtr() || t.IsUnsafePtr() {
                        base.ErrorfAt(ft.Embedlineno, errors.InvalidPtrEmbed, "embedded type cannot be a pointer")
                }
        }
}

func fieldsHasShape(fields []*Field) bool {
        for _, f := range fields {
                if f.Type != nil && f.Type.HasShape() {
                        return true
                }
        }
        return false
}

// newBasic returns a new basic type of the given kind.
func newBasic(kind Kind, obj Object) *Type {
        t := newType(kind)
        t.obj = obj
        return t
}

// NewInterface returns a new interface for the given methods and
// embedded types. Embedded types are specified as fields with no Sym.
func NewInterface(methods []*Field) *Type {
        t := newType(TINTER)
        t.SetInterface(methods)
        for _, f := range methods {
                // f.Type could be nil for a broken interface declaration
                if f.Type != nil && f.Type.HasShape() {
                        t.SetHasShape(true)
                        break
                }
        }
        return t
}

const BOGUS_FUNARG_OFFSET = -1000000000

func unzeroFieldOffsets(f []*Field) {
        for i := range f {
                f[i].Offset = BOGUS_FUNARG_OFFSET // This will cause an explosion if it is not corrected
        }
}

// NewSignature returns a new function type for the given receiver,
// parameters, and results, any of which may be nil.
func NewSignature(recv *Field, params, results []*Field) *Type {
        var recvs []*Field
        if recv != nil {
                recvs = []*Field{recv}
        }

        t := newType(TFUNC)
        ft := t.funcType()

        funargs := func(fields []*Field, funarg Funarg) *Type {
                s := NewStruct(fields)
                s.StructType().Funarg = funarg
                return s
        }

        if recv != nil {
                recv.Offset = BOGUS_FUNARG_OFFSET
        }
        unzeroFieldOffsets(params)
        unzeroFieldOffsets(results)
        ft.Receiver = funargs(recvs, FunargRcvr)
        ft.Params = funargs(params, FunargParams)
        ft.Results = funargs(results, FunargResults)
        if fieldsHasShape(recvs) || fieldsHasShape(params) || fieldsHasShape(results) {
                t.SetHasShape(true)
        }

        return t
}

// NewStruct returns a new struct with the given fields.
func NewStruct(fields []*Field) *Type {
        t := newType(TSTRUCT)
        t.setFields(fields)
        if fieldsHasShape(fields) {
                t.SetHasShape(true)
        }
        return t
}

var (
        IsInt     [NTYPE]bool
        IsFloat   [NTYPE]bool
        IsComplex [NTYPE]bool
        IsSimple  [NTYPE]bool
)

var IsOrdered [NTYPE]bool

// IsReflexive reports whether t has a reflexive equality operator.
// That is, if x==x for all x of type t.
func IsReflexive(t *Type) bool {
        switch t.Kind() {
        case TBOOL,
                TINT,
                TUINT,
                TINT8,
                TUINT8,
                TINT16,
                TUINT16,
                TINT32,
                TUINT32,
                TINT64,
                TUINT64,
                TUINTPTR,
                TPTR,
                TUNSAFEPTR,
                TSTRING,
                TCHAN:
                return true

        case TFLOAT32,
                TFLOAT64,
                TCOMPLEX64,
                TCOMPLEX128,
                TINTER:
                return false

        case TARRAY:
                return IsReflexive(t.Elem())

        case TSTRUCT:
                for _, t1 := range t.Fields() {
                        if !IsReflexive(t1.Type) {
                                return false
                        }
                }
                return true

        default:
                base.Fatalf("bad type for map key: %v", t)
                return false
        }
}

// Can this type be stored directly in an interface word?
// Yes, if the representation is a single pointer.
func IsDirectIface(t *Type) bool {
        switch t.Kind() {
        case TPTR:
                // Pointers to notinheap types must be stored indirectly. See issue 42076.
                return !t.Elem().NotInHeap()
        case TCHAN,
                TMAP,
                TFUNC,
                TUNSAFEPTR:
                return true

        case TARRAY:
                // Array of 1 direct iface type can be direct.
                return t.NumElem() == 1 && IsDirectIface(t.Elem())

        case TSTRUCT:
                // Struct with 1 field of direct iface type can be direct.
                return t.NumFields() == 1 && IsDirectIface(t.Field(0).Type)
        }

        return false
}

// IsInterfaceMethod reports whether (field) m is
// an interface method. Such methods have the
// special receiver type types.FakeRecvType().
func IsInterfaceMethod(f *Type) bool {
        return f.Recv().Type == FakeRecvType()
}

// IsMethodApplicable reports whether method m can be called on a
// value of type t. This is necessary because we compute a single
// method set for both T and *T, but some *T methods are not
// applicable to T receivers.
func IsMethodApplicable(t *Type, m *Field) bool {
        return t.IsPtr() || !m.Type.Recv().Type.IsPtr() || IsInterfaceMethod(m.Type) || m.Embedded == 2
}

// IsRuntimePkg reports whether p is package runtime.
func IsRuntimePkg(p *Pkg) bool {
        if base.Flag.CompilingRuntime && p == LocalPkg {
                return true
        }
        return p.Path == "runtime"
}

// IsReflectPkg reports whether p is package reflect.
func IsReflectPkg(p *Pkg) bool {
        return p.Path == "reflect"
}

// IsNoInstrumentPkg reports whether p is a package that
// should not be instrumented.
func IsNoInstrumentPkg(p *Pkg) bool {
        for _, np := range base.NoInstrumentPkgs {
                if p.Path == np {
                        return true
                }
        }
        return false
}

// IsNoRacePkg reports whether p is a package that
// should not be race instrumented.
func IsNoRacePkg(p *Pkg) bool {
        for _, np := range base.NoRacePkgs {
                if p.Path == np {
                        return true
                }
        }
        return false
}

// ReceiverBaseType returns the underlying type, if any,
// that owns methods with receiver parameter t.
// The result is either a named type or an anonymous struct.
func ReceiverBaseType(t *Type) *Type {
        if t == nil {
                return nil
        }

        // Strip away pointer if it's there.
        if t.IsPtr() {
                if t.Sym() != nil {
                        return nil
                }
                t = t.Elem()
                if t == nil {
                        return nil
                }
        }

        // Must be a named type or anonymous struct.
        if t.Sym() == nil && !t.IsStruct() {
                return nil
        }

        // Check types.
        if IsSimple[t.Kind()] {
                return t
        }
        switch t.Kind() {
        case TARRAY, TCHAN, TFUNC, TMAP, TSLICE, TSTRING, TSTRUCT:
                return t
        }
        return nil
}

func FloatForComplex(t *Type) *Type {
        switch t.Kind() {
        case TCOMPLEX64:
                return Types[TFLOAT32]
        case TCOMPLEX128:
                return Types[TFLOAT64]
        }
        base.Fatalf("unexpected type: %v", t)
        return nil
}

func ComplexForFloat(t *Type) *Type {
        switch t.Kind() {
        case TFLOAT32:
                return Types[TCOMPLEX64]
        case TFLOAT64:
                return Types[TCOMPLEX128]
        }
        base.Fatalf("unexpected type: %v", t)
        return nil
}

func TypeSym(t *Type) *Sym {
        return TypeSymLookup(TypeSymName(t))
}

func TypeSymLookup(name string) *Sym {
        typepkgmu.Lock()
        s := typepkg.Lookup(name)
        typepkgmu.Unlock()
        return s
}

func TypeSymName(t *Type) string {
        name := t.LinkString()
        // Use a separate symbol name for Noalg types for #17752.
        if TypeHasNoAlg(t) {
                name = "noalg." + name
        }
        return name
}

// Fake package for runtime type info (headers)
// Don't access directly, use typeLookup below.
var (
        typepkgmu sync.Mutex // protects typepkg lookups
        typepkg   = NewPkg("type", "type")
)

var SimType [NTYPE]Kind

// Fake package for shape types (see typecheck.Shapify()).
var ShapePkg = NewPkg("go.shape", "go.shape")