# This file is a part of Julia. License is MIT: https://julialang.org/license

# name and module reflection

"""
    nameof(m::Module) -> Symbol

Get the name of a `Module` as a [`Symbol`](@ref).

# Examples
```jldoctest
julia> nameof(Base.Broadcast)
:Broadcast
```
"""
nameof(m::Module) = ccall(:jl_module_name, Ref{Symbol}, (Any,), m)

"""
    parentmodule(m::Module) -> Module

Get a module's enclosing `Module`. `Main` is its own parent.

# Examples
```jldoctest
julia> parentmodule(Main)
Main

julia> parentmodule(Base.Broadcast)
Base
```
"""
parentmodule(m::Module) = ccall(:jl_module_parent, Ref{Module}, (Any,), m)

"""
    moduleroot(m::Module) -> Module

Find the root module of a given module. This is the first module in the chain of
parent modules of `m` which is either a registered root module or which is its
own parent module.
"""
function moduleroot(m::Module)
    while true
        is_root_module(m) && return m
        p = parentmodule(m)
        p == m && return m
        m = p
    end
end

"""
    @__MODULE__ -> Module

Get the `Module` of the toplevel eval,
which is the `Module` code is currently being read from.
"""
macro __MODULE__()
    return __module__
end

"""
    fullname(m::Module)

Get the fully-qualified name of a module as a tuple of symbols. For example,

# Examples
```jldoctest
julia> fullname(Base.Iterators)
(:Base, :Iterators)

julia> fullname(Main)
(:Main,)
```
"""
function fullname(m::Module)
    mn = nameof(m)
    if m === Main || m === Base || m === Core
        return (mn,)
    end
    mp = parentmodule(m)
    if mp === m
        return (mn,)
    end
    return (fullname(mp)..., mn)
end

"""
    names(x::Module; all::Bool = false, imported::Bool = false)

Get an array of the names exported by a `Module`, excluding deprecated names.
If `all` is true, then the list also includes non-exported names defined in the module,
deprecated names, and compiler-generated names.
If `imported` is true, then names explicitly imported from other modules
are also included.

As a special case, all names defined in `Main` are considered \"exported\",
since it is not idiomatic to explicitly export names from `Main`.
"""
names(m::Module; all::Bool = false, imported::Bool = false) =
    sort!(ccall(:jl_module_names, Array{Symbol,1}, (Any, Cint, Cint), m, all, imported))

isexported(m::Module, s::Symbol) = ccall(:jl_module_exports_p, Cint, (Any, Any), m, s) != 0
isdeprecated(m::Module, s::Symbol) = ccall(:jl_is_binding_deprecated, Cint, (Any, Any), m, s) != 0
isbindingresolved(m::Module, var::Symbol) = ccall(:jl_binding_resolved_p, Cint, (Any, Any), m, var) != 0

function binding_module(m::Module, s::Symbol)
    p = ccall(:jl_get_module_of_binding, Ptr{Cvoid}, (Any, Any), m, s)
    p == C_NULL && return m
    return unsafe_pointer_to_objref(p)::Module
end

function resolve(g::GlobalRef; force::Bool=false)
    if force || isbindingresolved(g.mod, g.name)
        return GlobalRef(binding_module(g.mod, g.name), g.name)
    end
    return g
end

const NamedTuple_typename = NamedTuple.body.body.name

function _fieldnames(@nospecialize t)
    if t.name === NamedTuple_typename
        if t.parameters[1] isa Tuple
            return t.parameters[1]
        else
            throw(ArgumentError("type does not have definite field names"))
        end
    end
    isdefined(t, :names) ? t.names : t.name.names
end

"""
    fieldname(x::DataType, i::Integer)

Get the name of field `i` of a `DataType`.

# Examples
```jldoctest
julia> fieldname(Rational, 1)
:num

julia> fieldname(Rational, 2)
:den
```
"""
function fieldname(t::DataType, i::Integer)
    if t.abstract
        throw(ArgumentError("type does not have definite field names"))
    end
    names = _fieldnames(t)
    n_fields = length(names)
    field_label = n_fields == 1 ? "field" : "fields"
    i > n_fields && throw(ArgumentError("Cannot access field $i since type $t only has $n_fields $field_label."))
    i < 1 && throw(ArgumentError("Field numbers must be positive integers. $i is invalid."))
    return names[i]::Symbol
end

fieldname(t::UnionAll, i::Integer) = fieldname(unwrap_unionall(t), i)
fieldname(t::Type{<:Tuple}, i::Integer) =
    i < 1 || i > fieldcount(t) ? throw(BoundsError(t, i)) : Int(i)

"""
    fieldnames(x::DataType)

Get a tuple with the names of the fields of a `DataType`.

# Examples
```jldoctest
julia> fieldnames(Rational)
(:num, :den)
```
"""
fieldnames(t::DataType) = (fieldcount(t); # error check to make sure type is specific enough
                           (_fieldnames(t)...,))
fieldnames(t::UnionAll) = fieldnames(unwrap_unionall(t))
fieldnames(::Core.TypeofBottom) =
    throw(ArgumentError("The empty type does not have field names since it does not have instances."))
fieldnames(t::Type{<:Tuple}) = ntuple(identity, fieldcount(t))

"""
    hasfield(T::Type, name::Symbol)

Return a boolean indicating whether `T` has `name` as one of its own fields.

!!! compat "Julia 1.2"
     This function requires at least Julia 1.2.
"""
function hasfield(::Type{T}, name::Symbol) where T
    @_pure_meta
    return fieldindex(T, name, false) > 0
end

"""
    nameof(t::DataType) -> Symbol

Get the name of a (potentially `UnionAll`-wrapped) `DataType` (without its parent module)
as a symbol.

# Examples
```jldoctest
julia> module Foo
           struct S{T}
           end
       end
Foo

julia> nameof(Foo.S{T} where T)
:S
```
"""
nameof(t::DataType) = t.name.name
nameof(t::UnionAll) = nameof(unwrap_unionall(t))::Symbol

"""
    parentmodule(t::DataType) -> Module

Determine the module containing the definition of a (potentially `UnionAll`-wrapped) `DataType`.

# Examples
```jldoctest
julia> module Foo
           struct Int end
       end
Foo

julia> parentmodule(Int)
Core

julia> parentmodule(Foo.Int)
Foo
```
"""
parentmodule(t::DataType) = t.name.module
parentmodule(t::UnionAll) = parentmodule(unwrap_unionall(t))

"""
    isconst(m::Module, s::Symbol) -> Bool

Determine whether a global is declared `const` in a given `Module`.
"""
isconst(m::Module, s::Symbol) =
    ccall(:jl_is_const, Cint, (Any, Any), m, s) != 0

"""
    @isdefined s -> Bool

Tests whether variable `s` is defined in the current scope.

See also [`isdefined`](@ref).

# Examples
```jldoctest
julia> function f()
           println(@isdefined x)
           x = 3
           println(@isdefined x)
       end
f (generic function with 1 method)

julia> f()
false
true
```
"""
macro isdefined(s::Symbol)
    return Expr(:isdefined, esc(s))
end

"""
    @locals()

Construct a dictionary of the names (as symbols) and values of all local
variables defined as of the call site.

!!! compat "Julia 1.1"
    This macro requires at least Julia 1.1.

# Examples
```jldoctest
julia> let x = 1, y = 2
           Base.@locals
       end
Dict{Symbol,Any} with 2 entries:
  :y => 2
  :x => 1

julia> function f(x)
           local y
           show(Base.@locals); println()
           for i = 1:1
               show(Base.@locals); println()
           end
           y = 2
           show(Base.@locals); println()
           nothing
       end;

julia> f(42)
Dict{Symbol,Any}(:x=>42)
Dict{Symbol,Any}(:i=>1,:x=>42)
Dict{Symbol,Any}(:y=>2,:x=>42)
```
"""
macro locals()
    return Expr(:locals)
end

"""
    objectid(x)

Get a hash value for `x` based on object identity. `objectid(x)==objectid(y)` if `x === y`.
"""
objectid(@nospecialize(x)) = ccall(:jl_object_id, UInt, (Any,), x)

# concrete datatype predicates

struct DataTypeLayout
    nfields::UInt32
    alignment::UInt32
    # alignment : 28;
    # haspadding : 1;
    # pointerfree : 1;
    # fielddesc_type : 2;
end

"""
    Base.datatype_alignment(dt::DataType) -> Int

Memory allocation minimum alignment for instances of this type.
Can be called on any `isconcretetype`.
"""
function datatype_alignment(dt::DataType)
    @_pure_meta
    dt.layout == C_NULL && throw(UndefRefError())
    alignment = unsafe_load(convert(Ptr{DataTypeLayout}, dt.layout)).alignment
    return Int(alignment & 0x1FF)
end

"""
    Base.datatype_haspadding(dt::DataType) -> Bool

Return whether the fields of instances of this type are packed in memory,
with no intervening padding bytes.
Can be called on any `isconcretetype`.
"""
function datatype_haspadding(dt::DataType)
    @_pure_meta
    dt.layout == C_NULL && throw(UndefRefError())
    alignment = unsafe_load(convert(Ptr{DataTypeLayout}, dt.layout)).alignment
    return (alignment >> 9) & 1 == 1
end

"""
    Base.datatype_pointerfree(dt::DataType) -> Bool

Return whether instances of this type can contain references to gc-managed memory.
Can be called on any `isconcretetype`.
"""
function datatype_pointerfree(dt::DataType)
    @_pure_meta
    dt.layout == C_NULL && throw(UndefRefError())
    alignment = unsafe_load(convert(Ptr{DataTypeLayout}, dt.layout)).alignment
    return (alignment >> 10) & 0xFFFFF == 0
end

"""
    Base.datatype_fielddesc_type(dt::DataType) -> Int

Return the size in bytes of each field-description entry in the layout array,
located at `(dt.layout + sizeof(DataTypeLayout))`.
Can be called on any `isconcretetype`.

See also [`Base.fieldoffset`](@ref).
"""
function datatype_fielddesc_type(dt::DataType)
    @_pure_meta
    dt.layout == C_NULL && throw(UndefRefError())
    alignment = unsafe_load(convert(Ptr{DataTypeLayout}, dt.layout)).alignment
    return (alignment >> 30) & 3
end

"""
    isimmutable(v) -> Bool

Return `true` iff value `v` is immutable.  See [Mutable Composite Types](@ref)
for a discussion of immutability. Note that this function works on values, so if you give it
a type, it will tell you that a value of `DataType` is mutable.

# Examples
```jldoctest
julia> isimmutable(1)
true

julia> isimmutable([1,2])
false
```
"""
isimmutable(@nospecialize(x)) = (@_pure_meta; !typeof(x).mutable)

"""
    Base.isstructtype(T) -> Bool

Determine whether type `T` was declared as a struct type
(i.e. using the `struct` or `mutable struct` keyword).
"""
function isstructtype(@nospecialize(t::Type))
    @_pure_meta
    t = unwrap_unionall(t)
    # TODO: what to do for `Union`?
    isa(t, DataType) || return false
    return length(t.types) != 0 || (t.size == 0 && !t.abstract)
end

"""
    Base.isprimitivetype(T) -> Bool

Determine whether type `T` was declared as a primitive type
(i.e. using the `primitive` keyword).
"""
function isprimitivetype(@nospecialize(t::Type))
    @_pure_meta
    t = unwrap_unionall(t)
    # TODO: what to do for `Union`?
    isa(t, DataType) || return false
    return length(t.types) == 0 && t.size != 0 && !t.abstract
end

"""
    isbitstype(T)

Return `true` if type `T` is a "plain data" type,
meaning it is immutable and contains no references to other values,
only `primitive` types and other `isbitstype` types.
Typical examples are numeric types such as [`UInt8`](@ref),
[`Float64`](@ref), and [`Complex{Float64}`](@ref).
This category of types is significant since they are valid as type parameters,
may not track [`isdefined`](@ref) / [`isassigned`](@ref) status,
and have a defined layout that is compatible with C.

# Examples
```jldoctest
julia> isbitstype(Complex{Float64})
true

julia> isbitstype(Complex)
false
```
"""
isbitstype(@nospecialize(t::Type)) = (@_pure_meta; isa(t, DataType) && t.isbitstype)

"""
    isbits(x)

Return `true` if `x` is an instance of an `isbitstype` type.
"""
isbits(@nospecialize x) = (@_pure_meta; typeof(x).isbitstype)

"""
    isdispatchtuple(T)

Determine whether type `T` is a tuple "leaf type",
meaning it could appear as a type signature in dispatch
and has no subtypes (or supertypes) which could appear in a call.
"""
isdispatchtuple(@nospecialize(t)) = (@_pure_meta; isa(t, DataType) && t.isdispatchtuple)

iskindtype(@nospecialize t) = (t === DataType || t === UnionAll || t === Union || t === typeof(Bottom))
isconcretedispatch(@nospecialize t) = isconcretetype(t) && !iskindtype(t)
has_free_typevars(@nospecialize(t)) = ccall(:jl_has_free_typevars, Cint, (Any,), t) != 0

# equivalent to isa(v, Type) && isdispatchtuple(Tuple{v}) || v === Union{}
# and is thus perhaps most similar to the old (pre-1.0) `isleaftype` query
const _TYPE_NAME = Type.body.name
function isdispatchelem(@nospecialize v)
    return (v === Bottom) || (v === typeof(Bottom)) || isconcretedispatch(v) ||
        (isa(v, DataType) && v.name === _TYPE_NAME && !has_free_typevars(v)) # isType(v)
end

"""
    isconcretetype(T)

Determine whether type `T` is a concrete type, meaning it could have direct instances
(values `x` such that `typeof(x) === T`).

# Examples
```jldoctest
julia> isconcretetype(Complex)
false

julia> isconcretetype(Complex{Float32})
true

julia> isconcretetype(Vector{Complex})
true

julia> isconcretetype(Vector{Complex{Float32}})
true

julia> isconcretetype(Union{})
false

julia> isconcretetype(Union{Int,String})
false
```
"""
isconcretetype(@nospecialize(t)) = (@_pure_meta; isa(t, DataType) && t.isconcretetype)

"""
    Base.isabstracttype(T)

Determine whether type `T` was declared as an abstract type
(i.e. using the `abstract` keyword).

# Examples
```jldoctest
julia> Base.isabstracttype(AbstractArray)
true

julia> Base.isabstracttype(Vector)
false
```
"""
function isabstracttype(@nospecialize(t))
    @_pure_meta
    t = unwrap_unionall(t)
    # TODO: what to do for `Union`?
    return isa(t, DataType) && t.abstract
end

"""
    Base.parameter_upper_bound(t::UnionAll, idx)

Determine the upper bound of a type parameter in the underlying datatype.
This method should generally not be relied upon:
code instead should usually use static parameters in dispatch to extract these values.

# Examples
```jldoctest
julia> struct Foo{T<:AbstractFloat, N}
           x::Tuple{T, N}
       end

julia> Base.parameter_upper_bound(Foo, 1)
AbstractFloat

julia> Base.parameter_upper_bound(Foo, 2)
Any
```
"""
function parameter_upper_bound(t::UnionAll, idx)
    @_pure_meta
    return rewrap_unionall((unwrap_unionall(t)::DataType).parameters[idx], t)
end

"""
    typeintersect(T, S)

Compute a type that contains the intersection of `T` and `S`. Usually this will be the
smallest such type or one close to it.
"""
typeintersect(@nospecialize(a),@nospecialize(b)) = (@_pure_meta; ccall(:jl_type_intersection, Any, (Any,Any), a, b))

"""
    fieldoffset(type, i)

The byte offset of field `i` of a type relative to the data start. For example, we could
use it in the following manner to summarize information about a struct:

```jldoctest
julia> structinfo(T) = [(fieldoffset(T,i), fieldname(T,i), fieldtype(T,i)) for i = 1:fieldcount(T)];

julia> structinfo(Base.Filesystem.StatStruct)
12-element Array{Tuple{UInt64,Symbol,DataType},1}:
 (0x0000000000000000, :device, UInt64)
 (0x0000000000000008, :inode, UInt64)
 (0x0000000000000010, :mode, UInt64)
 (0x0000000000000018, :nlink, Int64)
 (0x0000000000000020, :uid, UInt64)
 (0x0000000000000028, :gid, UInt64)
 (0x0000000000000030, :rdev, UInt64)
 (0x0000000000000038, :size, Int64)
 (0x0000000000000040, :blksize, Int64)
 (0x0000000000000048, :blocks, Int64)
 (0x0000000000000050, :mtime, Float64)
 (0x0000000000000058, :ctime, Float64)
```
"""
fieldoffset(x::DataType, idx::Integer) = (@_pure_meta; ccall(:jl_get_field_offset, Csize_t, (Any, Cint), x, idx))

"""
    fieldtype(T, name::Symbol | index::Int)

Determine the declared type of a field (specified by name or index) in a composite DataType `T`.

# Examples
```jldoctest
julia> struct Foo
           x::Int64
           y::String
       end

julia> fieldtype(Foo, :x)
Int64

julia> fieldtype(Foo, 2)
String
```
"""
fieldtype

"""
    fieldindex(T, name::Symbol, err:Bool=true)

Get the index of a named field, throwing an error if the field does not exist (when err==true)
or returning 0 (when err==false).

# Examples
```jldoctest
julia> struct Foo
           x::Int64
           y::String
       end

julia> Base.fieldindex(Foo, :z)
ERROR: type Foo has no field z
Stacktrace:
[...]

julia> Base.fieldindex(Foo, :z, false)
0
```
"""
function fieldindex(T::DataType, name::Symbol, err::Bool=true)
    return Int(ccall(:jl_field_index, Cint, (Any, Any, Cint), T, name, err)+1)
end

argument_datatype(@nospecialize t) = ccall(:jl_argument_datatype, Any, (Any,), t)
function argument_mt(@nospecialize t)
    dt = argument_datatype(t)
    (dt === nothing || !isdefined(dt.name, :mt)) && return nothing
    dt.name.mt
end

"""
    fieldcount(t::Type)

Get the number of fields that an instance of the given type would have.
An error is thrown if the type is too abstract to determine this.
"""
function fieldcount(@nospecialize t)
    if t isa UnionAll || t isa Union
        t = argument_datatype(t)
        if t === nothing
            throw(ArgumentError("type does not have a definite number of fields"))
        end
        t = t::DataType
    elseif t == Union{}
        throw(ArgumentError("The empty type does not have a well-defined number of fields since it does not have instances."))
    end
    if !(t isa DataType)
        throw(TypeError(:fieldcount, DataType, t))
    end
    if t.name === NamedTuple_typename
        names, types = t.parameters
        if names isa Tuple
            return length(names)
        end
        if types isa DataType && types <: Tuple
            return fieldcount(types)
        end
        abstr = true
    else
        abstr = t.abstract || (t.name === Tuple.name && isvatuple(t))
    end
    if abstr
        throw(ArgumentError("type does not have a definite number of fields"))
    end
    return length(t.types)
end

"""
    fieldtypes(T::Type)

The declared types of all fields in a composite DataType `T` as a tuple.

!!! compat "Julia 1.1"
    This function requires at least Julia 1.1.

# Examples
```jldoctest
julia> struct Foo
           x::Int64
           y::String
       end

julia> fieldtypes(Foo)
(Int64, String)
```
"""
fieldtypes(T::Type) = ntuple(i -> fieldtype(T, i), fieldcount(T))

# return all instances, for types that can be enumerated

"""
    instances(T::Type)

Return a collection of all instances of the given type, if applicable. Mostly used for
enumerated types (see `@enum`).

# Example
```jldoctest
julia> @enum Color red blue green

julia> instances(Color)
(red, blue, green)
```
"""
function instances end

function to_tuple_type(@nospecialize(t))
    @_pure_meta
    if isa(t,Tuple) || isa(t,AbstractArray) || isa(t,SimpleVector)
        t = Tuple{t...}
    end
    if isa(t,Type) && t<:Tuple
        for p in unwrap_unionall(t).parameters
            if !(isa(p,Type) || isa(p,TypeVar))
                error("argument tuple type must contain only types")
            end
        end
    else
        error("expected tuple type")
    end
    t
end

function signature_type(@nospecialize(f), @nospecialize(args))
    f_type = isa(f, Type) ? Type{f} : typeof(f)
    if isa(args, Type)
        u = unwrap_unionall(args)
        return rewrap_unionall(Tuple{f_type, u.parameters...}, args)
    else
        return Tuple{f_type, args...}
    end
end

"""
    code_lowered(f, types; generated=true, debuginfo=:default)

Return an array of the lowered forms (IR) for the methods matching the given generic function
and type signature.

If `generated` is `false`, the returned `CodeInfo` instances will correspond to fallback
implementations. An error is thrown if no fallback implementation exists.
If `generated` is `true`, these `CodeInfo` instances will correspond to the method bodies
yielded by expanding the generators.

The keyword debuginfo controls the amount of code metadata present in the output.

Note that an error will be thrown if `types` are not leaf types when `generated` is
`true` and any of the corresponding methods are an `@generated` method.
"""
function code_lowered(@nospecialize(f), @nospecialize(t=Tuple); generated::Bool=true, debuginfo::Symbol=:default)
    if @isdefined(IRShow)
        debuginfo = IRShow.debuginfo(debuginfo)
    elseif debuginfo == :default
        debuginfo = :source
    end
    if debuginfo != :source && debuginfo != :none
        throw(ArgumentError("'debuginfo' must be either :source or :none"))
    end
    return map(method_instances(f, t)) do m
        if generated && isgenerated(m)
            if may_invoke_generator(m)
                return ccall(:jl_code_for_staged, Any, (Any,), m)::CodeInfo
            else
                error("Could not expand generator for `@generated` method ", m, ". ",
                      "This can happen if the provided argument types (", t, ") are ",
                      "not leaf types, but the `generated` argument is `true`.")
            end
        end
        code = uncompressed_ast(m.def::Method)
        debuginfo == :none && remove_linenums!(code)
        return code
    end
end

isgenerated(m::Method) = isdefined(m, :generator)
isgenerated(m::Core.MethodInstance) = isgenerated(m.def)

# low-level method lookup functions used by the compiler

unionlen(x::Union) = unionlen(x.a) + unionlen(x.b)
unionlen(@nospecialize(x)) = 1

_uniontypes(x::Union, ts) = (_uniontypes(x.a,ts); _uniontypes(x.b,ts); ts)
_uniontypes(@nospecialize(x), ts) = (push!(ts, x); ts)
uniontypes(@nospecialize(x)) = _uniontypes(x, Any[])

function _methods(@nospecialize(f), @nospecialize(t), lim::Int, world::UInt)
    tt = signature_type(f, t)
    return _methods_by_ftype(tt, lim, world)
end

function _methods_by_ftype(@nospecialize(t), lim::Int, world::UInt)
    return _methods_by_ftype(t, lim, world, UInt[typemin(UInt)], UInt[typemax(UInt)])
end
function _methods_by_ftype(@nospecialize(t), lim::Int, world::UInt, min::Array{UInt,1}, max::Array{UInt,1})
    return ccall(:jl_matching_methods, Any, (Any, Cint, Cint, UInt, Ptr{UInt}, Ptr{UInt}), t, lim, 0, world, min, max)
end

# high-level, more convenient method lookup functions

# type for reflecting and pretty-printing a subset of methods
mutable struct MethodList
    ms::Array{Method,1}
    mt::Core.MethodTable
end

length(m::MethodList) = length(m.ms)
isempty(m::MethodList) = isempty(m.ms)
iterate(m::MethodList, s...) = iterate(m.ms, s...)
eltype(::Type{MethodList}) = Method

function MethodList(mt::Core.MethodTable)
    ms = Method[]
    visit(mt) do m
        push!(ms, m)
    end
    return MethodList(ms, mt)
end

"""
    methods(f, [types])

Returns the method table for `f`.

If `types` is specified, returns an array of methods whose types match.
"""
function methods(@nospecialize(f), @nospecialize(t))
    if isa(f, Core.Builtin)
        throw(ArgumentError("argument is not a generic function"))
    end
    t = to_tuple_type(t)
    world = typemax(UInt)
    return MethodList(Method[m[3] for m in _methods(f, t, -1, world)], typeof(f).name.mt)
end

methods(f::Core.Builtin) = MethodList(Method[], typeof(f).name.mt)

function methods_including_ambiguous(@nospecialize(f), @nospecialize(t))
    tt = signature_type(f, t)
    world = typemax(UInt)
    min = UInt[typemin(UInt)]
    max = UInt[typemax(UInt)]
    ms = ccall(:jl_matching_methods, Any, (Any, Cint, Cint, UInt, Ptr{UInt}, Ptr{UInt}), tt, -1, 1, world, min, max)::Array{Any,1}
    return MethodList(Method[m[3] for m in ms], typeof(f).name.mt)
end
function methods(@nospecialize(f))
    # return all matches
    return methods(f, Tuple{Vararg{Any}})
end

function visit(f, mt::Core.MethodTable)
    mt.defs !== nothing && visit(f, mt.defs)
    nothing
end
function visit(f, mc::Core.TypeMapLevel)
    if mc.targ !== nothing
        e = mc.targ::Vector{Any}
        for i in 1:length(e)
            isassigned(e, i) && visit(f, e[i])
        end
    end
    if mc.arg1 !== nothing
        e = mc.arg1::Vector{Any}
        for i in 1:length(e)
            isassigned(e, i) && visit(f, e[i])
        end
    end
    mc.list !== nothing && visit(f, mc.list)
    mc.any !== nothing && visit(f, mc.any)
    nothing
end
function visit(f, d::Core.TypeMapEntry)
    while d !== nothing
        f(d.func)
        d = d.next
    end
    nothing
end

function length(mt::Core.MethodTable)
    n = 0
    visit(mt) do m
        n += 1
    end
    return n::Int
end
isempty(mt::Core.MethodTable) = (mt.defs === nothing)

uncompressed_ast(m::Method) = isdefined(m, :source) ? _uncompressed_ast(m, m.source) :
                              isdefined(m, :generator) ? error("Method is @generated; try `code_lowered` instead.") :
                              error("Code for this Method is not available.")
_uncompressed_ast(m::Method, s::CodeInfo) = copy(s)
_uncompressed_ast(m::Method, s::Array{UInt8,1}) = ccall(:jl_uncompress_ast, Any, (Any, Ptr{Cvoid}, Any), m, C_NULL, s)::CodeInfo
_uncompressed_ast(ci::Core.CodeInstance, s::Array{UInt8,1}) = ccall(:jl_uncompress_ast, Any, (Any, Any, Any), ci.def.def::Method, ci, s)::CodeInfo

function method_instances(@nospecialize(f), @nospecialize(t), world::UInt = typemax(UInt))
    tt = signature_type(f, t)
    results = Core.MethodInstance[]
    for method_data in _methods_by_ftype(tt, -1, world)
        mtypes, msp, m = method_data
        instance = ccall(:jl_specializations_get_linfo, Ref{MethodInstance}, (Any, Any, Any), m, mtypes, msp)
        push!(results, instance)
    end
    return results
end

# this type mirrors jl_cgparams_t (documented in julia.h)
struct CodegenParams
    cached::Cint

    track_allocations::Cint
    code_coverage::Cint
    static_alloc::Cint
    prefer_specsig::Cint

    module_setup::Any
    module_activation::Any
    raise_exception::Any
    emit_function::Any
    emitted_function::Any

    CodegenParams(;cached::Bool=true,
                   track_allocations::Bool=true, code_coverage::Bool=true,
                   static_alloc::Bool=true, prefer_specsig::Bool=false,
                   module_setup=nothing, module_activation=nothing, raise_exception=nothing,
                   emit_function=nothing, emitted_function=nothing) =
        new(Cint(cached),
            Cint(track_allocations), Cint(code_coverage),
            Cint(static_alloc), Cint(prefer_specsig),
            module_setup, module_activation, raise_exception,
            emit_function, emitted_function)
end

const SLOT_USED = 0x8
ast_slotflag(@nospecialize(code), i) = ccall(:jl_ast_slotflag, UInt8, (Any, Csize_t), code, i - 1)

"""
    may_invoke_generator(method, atypes, sparams)

Computes whether or not we may invoke the generator for the given `method` on
the given atypes and sparams. For correctness, all generated function are
required to return monotonic answers. However, since we don't expect users to
be able to successfully implement this criterion, we only call generated
functions on concrete types. The one exception to this is that we allow calling
generators with abstract types if the generator does not use said abstract type
(and thus cannot incorrectly use it to break monotonicity). This function
computes whether we are in either of these cases.

Unlike normal functions, the compilation heuristics still can't generate good dispatch
in some cases, but this may still allow inference not to fall over in some limited cases.
"""
function may_invoke_generator(method::MethodInstance)
    return may_invoke_generator(method.def::Method, method.specTypes, method.sparam_vals)
end
function may_invoke_generator(method::Method, @nospecialize(atypes), sparams::SimpleVector)
    # If we have complete information, we may always call the generator
    isdispatchtuple(atypes) && return true

    # We don't have complete information, but it is possible that the generator
    # syntactically doesn't make use of the information we don't have. Check
    # for that.

    # For now, only handle the (common, generated by the frontend case) that the
    # generator only has one method
    isa(method.generator, Core.GeneratedFunctionStub) || return false
    gen_mthds = methods(method.generator.gen)
    length(gen_mthds) == 1 || return false

    generator_method = first(gen_mthds)
    nsparams = length(sparams)
    isdefined(generator_method, :source) || return false
    code = generator_method.source
    nslots = ccall(:jl_ast_nslots, Int, (Any,), code)
    at = unwrap_unionall(atypes)
    (nslots >= 1 + length(sparams) + length(at.parameters)) || return false

    for i = 1:nsparams
        if isa(sparams[i], TypeVar)
            if (ast_slotflag(code, 1 + i) & SLOT_USED) != 0
                return false
            end
        end
    end
    for i = 1:length(at.parameters)
        if !isdispatchelem(at.parameters[i])
            if (ast_slotflag(code, 1 + i + nsparams) & SLOT_USED) != 0
                return false
            end
        end
    end
    return true
end

# give a decent error message if we try to instantiate a staged function on non-leaf types
function func_for_method_checked(m::Method, @nospecialize(types), sparams::SimpleVector)
    if isdefined(m, :generator) && !may_invoke_generator(m, types, sparams)
        error("cannot call @generated function `", m, "` ",
              "with abstract argument types: ", types)
    end
    return m
end

function func_for_method_checked(m::Method, @nospecialize(types))
    depwarn("The two argument form of `func_for_method_checked` is deprecated. Pass sparams in addition.",
            :func_for_method_checked)
    if isdefined(m, :generator) && !isdispatchtuple(types)
        error("cannot call @generated function `", m, "` ",
              "with abstract argument types: ", types)
    end
    return m
end


"""
    code_typed(f, types; optimize=true, debuginfo=:default)

Returns an array of type-inferred lowered form (IR) for the methods matching the given
generic function and type signature. The keyword argument `optimize` controls whether
additional optimizations, such as inlining, are also applied.
The keyword `debuginfo` controls the amount of code metadata present in the output,
possible options are `:source` or `:none`.
"""
function code_typed(@nospecialize(f), @nospecialize(types=Tuple);
                    optimize=true,
                    debuginfo::Symbol=:default,
                    world = get_world_counter(),
                    params = Core.Compiler.Params(world))
    ccall(:jl_is_in_pure_context, Bool, ()) && error("code reflection cannot be used from generated functions")
    if isa(f, Core.Builtin)
        throw(ArgumentError("argument is not a generic function"))
    end
    if @isdefined(IRShow)
        debuginfo = IRShow.debuginfo(debuginfo)
    elseif debuginfo == :default
        debuginfo = :source
    end
    if debuginfo != :source && debuginfo != :none
        throw(ArgumentError("'debuginfo' must be either :source or :none"))
    end
    types = to_tuple_type(types)
    asts = []
    for x in _methods(f, types, -1, world)
        meth = func_for_method_checked(x[3], types, x[2])
        (code, ty) = Core.Compiler.typeinf_code(meth, x[1], x[2], optimize, params)
        code === nothing && error("inference not successful") # inference disabled?
        debuginfo == :none && remove_linenums!(code)
        push!(asts, code => ty)
    end
    return asts
end

function return_types(@nospecialize(f), @nospecialize(types=Tuple))
    ccall(:jl_is_in_pure_context, Bool, ()) && error("code reflection cannot be used from generated functions")
    if isa(f, Core.Builtin)
        throw(ArgumentError("argument is not a generic function"))
    end
    types = to_tuple_type(types)
    rt = []
    world = get_world_counter()
    params = Core.Compiler.Params(world)
    for x in _methods(f, types, -1, world)
        meth = func_for_method_checked(x[3], types, x[2])
        ty = Core.Compiler.typeinf_type(meth, x[1], x[2], params)
        ty === nothing && error("inference not successful") # inference disabled?
        push!(rt, ty)
    end
    return rt
end

"""
    which(f, types)

Returns the method of `f` (a `Method` object) that would be called for arguments of the given `types`.

If `types` is an abstract type, then the method that would be called by `invoke` is returned.
"""
function which(@nospecialize(f), @nospecialize(t))
    if isa(f, Core.Builtin)
        throw(ArgumentError("argument is not a generic function"))
    end
    t = to_tuple_type(t)
    tt = signature_type(f, t)
    m = ccall(:jl_gf_invoke_lookup, Any, (Any, UInt), tt, typemax(UInt))
    if m === nothing
        error("no unique matching method found for the specified argument types")
    end
    return m.func::Method
end

"""
    which(module, symbol)

Return the module in which the binding for the variable referenced by `symbol` in `module` was created.
"""
function which(m::Module, s::Symbol)
    if !isdefined(m, s)
        error("\"$s\" is not defined in module $m")
    end
    return binding_module(m, s)
end

# function reflection
"""
    nameof(f::Function) -> Symbol

Get the name of a generic `Function` as a symbol, or `:anonymous`.
"""
nameof(f::Function) = (typeof(f).name.mt::Core.MethodTable).name

functionloc(m::Core.MethodInstance) = functionloc(m.def)

"""
    functionloc(m::Method)

Returns a tuple `(filename,line)` giving the location of a `Method` definition.
"""
function functionloc(m::Method)
    ln = m.line
    if ln <= 0
        error("could not determine location of method definition")
    end
    return (find_source_file(string(m.file)), ln)
end

"""
    functionloc(f::Function, types)

Returns a tuple `(filename,line)` giving the location of a generic `Function` definition.
"""
functionloc(@nospecialize(f), @nospecialize(types)) = functionloc(which(f,types))

function functionloc(@nospecialize(f))
    mt = methods(f)
    if isempty(mt)
        if isa(f, Function)
            error("function has no definitions")
        else
            error("object is not callable")
        end
    end
    if length(mt) > 1
        error("function has multiple methods; please specify a type signature")
    end
    return functionloc(first(mt))
end

"""
    parentmodule(f::Function) -> Module

Determine the module containing the (first) definition of a generic
function.
"""
parentmodule(f::Function) = parentmodule(typeof(f))

"""
    parentmodule(f::Function, types) -> Module

Determine the module containing a given definition of a generic function.
"""
function parentmodule(@nospecialize(f), @nospecialize(types))
    m = methods(f, types)
    if isempty(m)
        error("no matching methods")
    end
    return first(m).module
end

"""
    hasmethod(f, t::Type{<:Tuple}[, kwnames]; world=typemax(UInt)) -> Bool

Determine whether the given generic function has a method matching the given
`Tuple` of argument types with the upper bound of world age given by `world`.

If a tuple of keyword argument names `kwnames` is provided, this also checks
whether the method of `f` matching `t` has the given keyword argument names.
If the matching method accepts a variable number of keyword arguments, e.g.
with `kwargs...`, any names given in `kwnames` are considered valid. Otherwise
the provided names must be a subset of the method's keyword arguments.

See also [`applicable`](@ref).

!!! compat "Julia 1.2"
    Providing keyword argument names requires Julia 1.2 or later.

# Examples
```jldoctest
julia> hasmethod(length, Tuple{Array})
true

julia> hasmethod(sum, Tuple{Function, Array}, (:dims,))
true

julia> hasmethod(sum, Tuple{Function, Array}, (:apples, :bananas))
false

julia> g(; xs...) = 4;

julia> hasmethod(g, Tuple{}, (:a, :b, :c, :d))  # g accepts arbitrary kwargs
true
```
"""
function hasmethod(@nospecialize(f), @nospecialize(t); world=typemax(UInt))
    t = to_tuple_type(t)
    t = signature_type(f, t)
    return ccall(:jl_gf_invoke_lookup, Any, (Any, UInt), t, world) !== nothing
end

function hasmethod(@nospecialize(f), @nospecialize(t), kwnames::Tuple{Vararg{Symbol}}; world=typemax(UInt))
    # TODO: this appears to be doing the wrong queries
    hasmethod(f, t, world=world) || return false
    isempty(kwnames) && return true
    m = which(f, t)
    kws = kwarg_decl(m, Core.kwftype(typeof(f)))
    for kw in kws
        endswith(String(kw), "...") && return true
    end
    return issubset(kwnames, kws)
end

"""
    isambiguous(m1, m2; ambiguous_bottom=false) -> Bool

Determine whether two methods `m1` and `m2` (typically of the same
function) are ambiguous.  This test is performed in the context of
other methods of the same function; in isolation, `m1` and `m2` might
be ambiguous, but if a third method resolving the ambiguity has been
defined, this returns `false`.

For parametric types, the `ambiguous_bottom` keyword argument controls whether
`Union{}` counts as an ambiguous intersection of type parameters – when `true`,
it is considered ambiguous, when `false` it is not.

# Examples
```jldoctest
julia> foo(x::Complex{<:Integer}) = 1
foo (generic function with 1 method)

julia> foo(x::Complex{<:Rational}) = 2
foo (generic function with 2 methods)

julia> m1, m2 = collect(methods(foo));

julia> typeintersect(m1.sig, m2.sig)
Tuple{#foo,Complex{Union{}}}

julia> Base.isambiguous(m1, m2, ambiguous_bottom=true)
true

julia> Base.isambiguous(m1, m2, ambiguous_bottom=false)
false
```
"""
function isambiguous(m1::Method, m2::Method; ambiguous_bottom::Bool=false)
    ti = typeintersect(m1.sig, m2.sig)
    ti === Bottom && return false
    if !ambiguous_bottom
        has_bottom_parameter(ti) && return false
    end
    ml = _methods_by_ftype(ti, -1, typemax(UInt))
    isempty(ml) && return true
    for m in ml
        if ti <: m[3].sig
            return false
        end
    end
    return true
end

"""
    delete_method(m::Method)

Make method `m` uncallable and force recompilation of any methods that use(d) it.
"""
function delete_method(m::Method)
    ccall(:jl_method_table_disable, Cvoid, (Any, Any), get_methodtable(m), m)
end

function get_methodtable(m::Method)
    ft = ccall(:jl_first_argument_datatype, Any, (Any,), m.sig)
    (ft::DataType).name.mt
end

"""
    has_bottom_parameter(t) -> Bool

Determine whether `t` is a Type for which one or more of its parameters is `Union{}`.
"""
function has_bottom_parameter(t::Type)
    ret = false
    for p in t.parameters
        ret |= (p == Bottom) || has_bottom_parameter(p)
    end
    ret
end
has_bottom_parameter(t::UnionAll) = has_bottom_parameter(unwrap_unionall(t))
has_bottom_parameter(t::Union) = has_bottom_parameter(t.a) & has_bottom_parameter(t.b)
has_bottom_parameter(t::TypeVar) = t.ub == Bottom || has_bottom_parameter(t.ub)
has_bottom_parameter(::Any) = false

min_world(m::Core.CodeInstance) = reinterpret(UInt, m.min_world)
max_world(m::Core.CodeInstance) = reinterpret(UInt, m.max_world)
min_world(m::Core.CodeInfo) = reinterpret(UInt, m.min_world)
max_world(m::Core.CodeInfo) = reinterpret(UInt, m.max_world)
get_world_counter() = ccall(:jl_get_world_counter, UInt, ())


"""
    propertynames(x, private=false)

Get a tuple or a vector of the properties (`x.property`) of an object `x`.
This is typically the same as [`fieldnames(typeof(x))`](@ref), but types
that overload [`getproperty`](@ref) should generally overload `propertynames`
as well to get the properties of an instance of the type.

`propertynames(x)` may return only "public" property names that are part
of the documented interface of `x`.   If you want it to also return "private"
fieldnames intended for internal use, pass `true` for the optional second argument.
REPL tab completion on `x.` shows only the `private=false` properties.
"""
propertynames(x) = fieldnames(typeof(x))
propertynames(m::Module) = names(m)
propertynames(x, private) = propertynames(x) # ignore private flag by default

"""
    hasproperty(x, s::Symbol)

Return a boolean indicating whether the object `x` has `s` as one of its own properties.

!!! compat "Julia 1.2"
     This function requires at least Julia 1.2.
"""
hasproperty(x, s::Symbol) = s in propertynames(x)
