path: root/nomsu_compiler.moon

-- This file contains the source code of the Nomsu compiler.
-- Nomsu is a programming language that cross-compiles to Lua. It was designed to be good
-- at natural-language-like code that is highly self-modifying and flexible.
-- The only dependency is LPEG, which can be installed using "luarocks install lpeg"
-- File usage:
--    Either, in a lua/moonscript file:
--        Nomsu = require "nomsu"
--        nomsu = Nomsu()
--        nomsu:run(your_nomsu_code)
--    Or from the command line:
--        lua nomsu.lua your_file.nom
lpeg = require 'lpeg'
{:R,:P,:S} = lpeg
re = require 're'
utils = require 'utils'
Files = require 'files'
{:stringify, :equivalent} = utils
{:List, :Dict, :Text} = require 'containers'
export colors, colored
colors = require 'consolecolors'
colored = setmetatable({}, {__index:(_,color)-> ((msg)-> colors[color]..tostring(msg or '')..colors.reset)})
{:insert, :remove, :concat} = table
unpack or= table.unpack
{:match, :sub, :gsub, :format, :byte, :find} = string
{:NomsuCode, :LuaCode, :Source} = require "code_obj"
SyntaxTree = require "syntax_tree"
make_parser = require("parser")
pretty_error = require("pretty_errors")
-- Mapping from source string (e.g. "@core/metaprogramming.nom[1:100]") to a mapping
-- from lua line number to nomsu line number
export SOURCE_MAP
SOURCE_MAP = {}

table.map = (t, fn)-> setmetatable([fn(v) for _,v in ipairs(t)], getmetatable(t))
table.fork = (t, values)-> setmetatable(values or {}, {__index:t})
table.copy = (t)-> setmetatable({k,v for k,v in pairs(t)}, getmetatable(t))

-- Parsing helper functions
utf8_char_patt = (
    R("\194\223")*R("\128\191") +
    R("\224\239")*R("\128\191")*R("\128\191") +
    R("\240\244")*R("\128\191")*R("\128\191")*R("\128\191"))
operator_patt = S("'`~!@$^&*+=|<>?/-")^1 * -1
identifier_patt = (R("az","AZ","09") + P("_") + utf8_char_patt)^1 * -1

is_operator = (s)->
    return not not operator_patt\match(s)

is_identifier = (s)->
    return not not identifier_patt\match(s)

inline_escaper = re.compile("{~ (%utf8_char / ('\"' -> '\\\"') / ('\n' -> '\\n') / ('\t' -> '\\t') / ('\b' -> '\\b') / ('\a' -> '\\a') / ('\v' -> '\\v') / ('\f' -> '\\f') / ('\r' -> '\\r') / ('\\' -> '\\\\') / ([^ -~] -> escape) / .)* ~}", {utf8_char: utf8_char_patt, escape:(=> ("\\%03d")\format(@byte!))})
inline_escape = (s)->
    return inline_escaper\match(s)

escaper = re.compile("{~ (%utf8_char / ('\\' -> '\\\\') / [\n\r\t -~] / (. -> escape))* ~}",
    {utf8_char: utf8_char_patt, escape:(=> ("\\%03d")\format(@byte!))})
escape = (s)->
    return escaper\match(s)

-- TODO:
-- Re-implement nomsu-to-lua comment translation?

make_tree = (tree, userdata)->
    tree.source = Source(userdata.filename, tree.start, tree.stop)
    tree.start, tree.stop = nil, nil
    tree.comments = [t for t in *tree when SyntaxTree\is_instance(t) and t.type == "Comment"]
    if #tree.comments == 0 then tree.comments = nil
    for i=#tree,1,-1
        if SyntaxTree\is_instance(tree[i]) and tree[i].type == "Comment"
            table.remove(tree, i)
    tree = SyntaxTree(tree)
    return tree

Parsers = {}
max_parser_version = 4
for version=1,max_parser_version
    peg_file = io.open("nomsu.#{version}.peg")
    if not peg_file and package.nomsupath
        for path in package.nomsupath\gmatch("[^;]+")
            peg_file = io.open(path.."/nomsu.#{version}.peg")
            break if peg_file
    assert(peg_file, "could not find nomsu .peg file")
    peg_contents = peg_file\read('*a')
    peg_file\close!
    Parsers[version] = make_parser(peg_contents, make_tree)

MAX_LINE = 80 -- For beautification purposes, try not to make lines much longer than this value
NomsuCompiler = setmetatable {}, {__tostring: => "Nomsu"}
_anon_chunk = 0
with NomsuCompiler
    .can_optimize = -> false

    -- Discretionary/convenience stuff
    .environment = {
        NOMSU_COMPILER_VERSION: 10, NOMSU_SYNTAX_VERSION: max_parser_version
        -- Lua stuff:
        :next, :unpack, :setmetatable, :coroutine, :rawequal, :getmetatable, :pcall,
        :error, :package, :os, :require, :tonumber, :tostring, :string, :xpcall, :module,
        :print, :loadfile, :rawset, :_VERSION, :collectgarbage, :rawget, :rawlen,
        :table, :assert, :dofile, :loadstring, lua_type_of_1:type, :select, :math, :io, :load,
        :pairs, :ipairs,
        -- Nomsu types:
        _List:List, _Dict:Dict,
        -- Utilities and misc.
        stringify:stringify, utils:utils, lpeg:lpeg, re:re, Files:Files,
        :SyntaxTree, TESTS: Dict({}), globals: Dict({}),
        :LuaCode, :NomsuCode, :Source
        nomsu:NomsuCompiler
        __imported: Dict{}
        __parent: nil
    }
    setmetatable(.environment, {
        __index: (key)=>
            if imported = rawget(@, "__imported")
                ret = imported[key]
                return ret unless ret == nil
            if parent = rawget(@, "__parent")
                return parent[key]
    })

    if _VERSION == "Lua 5.4"
        .environment.ipairs = (x)->
            if mt = getmetatable(x)
                if mt.__ipairs then return mt.__ipairs(x)
            return ipairs(x)
    if jit or _VERSION == "Lua 5.2"
        .environment.bit = require("bitops")

    .fork = =>
        f = setmetatable({}, {__index:@})
        f.environment = setmetatable({
            __parent: @environment
            __imported: Dict{}
            nomsu: f
            COMPILE_ACTIONS: setmetatable({
                __parent: @environment.COMPILE_ACTIONS
                __imported: Dict{}
            }, getmetatable(@environment))
        }, getmetatable(@environment))
        return f

    .parse = (nomsu_code, source=nil, version=nil)=>
        source or= nomsu_code.source
        nomsu_code = tostring(nomsu_code)
        unless source
            source = Source("anonymous chunk ##{_anon_chunk}", 1, #nomsu_code)
            _anon_chunk += 1
        version or= nomsu_code\match("^#![^\n]*nomsu[ ]+-V[ ]*([0-9.]+)")
        syntax_version = version and tonumber(version\match("^[0-9]+")) or max_parser_version
        parse = Parsers[syntax_version] or Parsers[max_parser_version]
        tree = parse(nomsu_code, source.filename)
        find_errors = (t)->
            if t.type == "Error"
                coroutine.yield t
            else
                for k,v in pairs(t)
                    continue unless SyntaxTree\is_instance(v)
                    find_errors(v)

        errs = [err for err in coroutine.wrap(-> find_errors(tree))]
        num_errs = #errs
        if num_errs > 0
            err_strings = [pretty_error{
                    title:"Parse error"
                    error:t.error, hint:t.hint, source:t\get_source_code!
                    start:t.source.start, stop:t.source.stop, filename:t.source.filename
                } for i, t in ipairs(errs) when i <= 3]
            if num_errs > 3
                table.insert(err_strings, "\027[31;1m +#{num_errs-#errs} additional errors...\027[0m\n")
            error(table.concat(err_strings, '\n\n'), 0)
        return tree

    .compile_error = (tree, err_msg, hint=nil)=>
        err_str = pretty_error{
            title: "Compile error"
            error:err_msg, hint:hint, source:tree\get_source_code!
            start:tree.source.start, stop:tree.source.stop, filename:tree.source.filename
        }
        error(err_str, 0)

    add_lua_bits = (val_or_stmt, code, compile_actions)=>
        cls = val_or_stmt == "value" and LuaCode.Value or LuaCode
        operate_on_text = (text)->
            lua = cls(text.source)
            for bit in *text
                if type(bit) == "string"
                    lua\append bit
                elseif bit.type == "Text"
                    lua\append(operate_on_text(bit))
                else
                    bit_lua = @compile(bit, compile_actions)
                    unless bit_lua.is_value
                        @compile_error bit,
                            "Can't use this as a string interpolation value, since it's not an expression."
                    lua\append bit_lua
            return lua
        return operate_on_text code

    add_lua_string_bits = (val_or_stmt, code)=>
        cls_str = val_or_stmt == "value" and "LuaCode.Value(" or "LuaCode("
        if code.type != "Text"
            return LuaCode.Value(code.source, cls_str, tostring(code.source)\as_lua!, ", ", @compile(code), ")")
        add_bit_lua = (lua, bit_lua)->
            bit_leading_len = #(bit_lua\match("^[^\n]*"))
            lua\append(lua\trailing_line_len! + bit_leading_len > MAX_LINE and ",\n    " or ", ")
            lua\append(bit_lua)
        operate_on_text = (text)->
            lua = LuaCode.Value(text.source, cls_str, tostring(text.source)\as_lua!)
            for bit in *text
                if type(bit) == "string"
                    add_bit_lua(lua, bit\as_lua!)
                elseif bit.type == "Text"
                    add_bit_lua(lua, operate_on_text(bit))
                else
                    bit_lua = @compile(bit)
                    unless bit_lua.is_value
                        @compile_error bit,
                            "Can't use this as a string interpolation value, since it's not an expression."
                    add_bit_lua(lua, bit_lua)
            lua\append ")"
            return lua
        return operate_on_text code

    -- This is a bit of a hack, but this code handles arbitrarily complex
    -- math expressions like 2*x + 3^2 without having to define a single
    -- action for every possibility.
    math_expression = re.compile [[ ([+-] " ")* [0-9]+ (" " [*/^+-] (" " [+-])* " " [0-9]+)+ !. ]]
    compile_math_expression = (tree, ...)=>
        lua = LuaCode.Value(tree.source)
        for i,tok in ipairs tree
            if type(tok) == 'string'
                lua\append tok
            else
                tok_lua = @compile(tok, compile_actions)
                unless tok_lua.is_value
                    @compile_error tok,
                        "Can't use this as a value in a math expression, since it's not a value."
                tok_lua\parenthesize! if tok.type == "Action"
                lua\append tok_lua
            lua\append " " if i < #tree
        return lua
    .environment.COMPILE_ACTIONS = setmetatable({
        __imported: Dict{}
        ["Lua 1"]: (tree, code)=>
            return add_lua_string_bits(@, 'statements', code)
    
        ["Lua value 1"]: (tree, code)=>
            return add_lua_string_bits(@, 'value', code)

        ["lua > 1"]: (tree, code)=>
            if code.type != "Text"
                return LuaCode tree.source, "nomsu:run_lua(", @compile(code), ", nomsu);"
            return add_lua_bits(@, "statements", code)

        ["= lua 1"]: (tree, code)=>
            if code.type != "Text"
                return LuaCode.Value tree.source, "nomsu:run_lua(", @compile(code), ":as_statements('return '), nomsu)"
            return add_lua_bits(@, "value", code)

        ["use 1"]: (tree, path)=>
            if path.type == 'Text' and #path == 1 and type(path[1]) == 'string'
                @import_file(path[1])
            return LuaCode(tree.source, "nomsu:import_file(#{@compile(path)})")

        ["tests"]: (tree)=> LuaCode.Value(tree.source, "TESTS")
        ["test 1"]: (tree, body)=>
            test_str = table.concat [tostring(@tree_to_nomsu(line)) for line in *body], "\n"
            LuaCode tree.source, "TESTS[#{tostring(tree.source)\as_lua!}] = ", test_str\as_lua!

        ["is jit"]: (tree, code)=>
            return LuaCode.Value(tree.source, jit and "true" or "false")

        ["Lua version"]: (tree, code)=>
            return LuaCode.Value(tree.source, _VERSION\as_lua!)

        __parent: setmetatable({}, {
            __index: (key)=>
                if type(key) == 'string' and math_expression\match(key)
                    return compile_math_expression
        })
    }, getmetatable(.environment))

    .import = (mod)=>
        for k,v in pairs(mod)
            continue if k == "__imported" or k == "__parent"
            @environment.__imported[k] = v
        for k,v in pairs(mod.COMPILE_ACTIONS)
            continue if k == "__imported" or k == "__parent"
            @environment.COMPILE_ACTIONS.__imported[k] or= v

    .import_file = (path)=>
        for _,f in Files.walk(path)
            if match(f, "%.lua$") or match(f, "%.nom$") or match(f, "^/dev/fd/[012]$")
                @import(@run_file(f))

    .run = (to_run, compile_actions)=>
        source = to_run.source or Source(to_run, 1, #to_run)
        if type(source) == 'string' then source = Source\from_string(source)
        if not Files.read(source.filename) then Files.spoof(source.filename, to_run)
        tree = if SyntaxTree\is_instance(to_run) then to_run else @parse(to_run, source)
        if tree == nil -- Happens if pattern matches, but there are no captures, e.g. an empty string
            return nil
        if tree.type != "FileChunks"
            tree = {tree}
        -- Each chunk's compilation is affected by the code in the previous chunks
        -- (typically), so each chunk needs to compile and run before the next one
        -- compiles.
        ret = nil
        all_lua = {}
        for chunk in *tree
            lua = @compile(chunk, compile_actions)\as_statements("return ")
            lua\declare_locals!
            lua\prepend "-- File: #{source.filename\gsub("\n.*", "...")}\n"
            insert all_lua, tostring(lua)
            ret = @run_lua(lua)
        return ret

    _running_files = {} -- For detecting circular imports
    _loaded_files = {}
    .run_file = (filename, compile_actions)=>
        -- Filename should be an absolute path, i.e. package.nomsupath will not be searched for it
        if _loaded_files[filename]
            return _loaded_files[filename]
        -- Check for circular import
        -- TODO: optimize?
        for i,running in ipairs _running_files
            if running == filename
                loop = [_running_files[j] for j=i,#_running_files]
                insert loop, filename
                error("Circular import, this loops forever: #{concat loop, " -> "}...")

        insert _running_files, filename
        mod = @fork!
        ret = mod.environment
        mod.from_file = filename
        if match(filename, "%.lua$")
            file = assert(Files.read(filename), "Could not find file: #{filename}")
            ret = mod\run_lua(LuaCode(Source(filename, 1, #file), file)) or ret
        elseif match(filename, "%.nom$") or match(filename, "^/dev/fd/[012]$")
            ran_lua = if @.can_optimize(filename) -- Look for precompiled version
                lua_filename = gsub(filename, "%.nom$", ".lua")
                if file = Files.read(lua_filename)
                    ret = mod\run_lua(LuaCode(Source(lua_filename, 1, #file), file)) or ret
                    true
            unless ran_lua
                file = Files.read(filename)
                if not file
                    error("Tried to run file that does not exist: #{filename}")
                ret = mod\run(NomsuCode(Source(filename,1,#file), file), compile_actions) or ret
        else
            error("Invalid filetype for #{filename}", 0)
        _loaded_files[filename] = ret
        remove _running_files
        return ret

    .run_lua = (lua)=>
        lua_string = tostring(lua)
        run_lua_fn, err = load(lua_string, tostring(source or lua.source), "t", @environment)
        if not run_lua_fn
            line_numbered_lua = concat(
                [format("%3d|%s",i,line) for i, line in ipairs Files.get_lines(lua_string)],
                "\n")
            error("Failed to compile generated code:\n#{colored.bright colored.blue colored.onblack line_numbered_lua}\n\n#{err}", 0)
        source = lua.source or Source(lua_string, 1, #lua_string)
        source_key = tostring(source)
        unless SOURCE_MAP[source_key]
            map = {}
            file = Files.read(source.filename)
            if not file
                error "Failed to find file: #{source.filename}"
            nomsu_str = file\sub(source.start, source.stop)
            assert type(nomsu_str) == 'string'
            lua_line = 1
            nomsu_line = Files.get_line_number(file, source.start)
            map_sources = (s)->
                if type(s) == 'string'
                    for nl in s\gmatch("\n")
                        map[lua_line] or= nomsu_line
                        lua_line += 1
                else
                    if s.source and s.source.filename == source.filename
                        nomsu_line = Files.get_line_number(file, s.source.start)
                    for b in *s.bits do map_sources(b)
            map_sources(lua)
            map[lua_line] or= nomsu_line
            map[0] = 0
            -- Mapping from lua line number to nomsu line numbers
            SOURCE_MAP[source_key] = map

        return run_lua_fn!

    .compile = (tree, compile_actions, force_value=false)=>
        compile_actions or= @environment.COMPILE_ACTIONS
        if tree.version
            if get_version = @[("Nomsu version")\as_lua_id!]
                if upgrade = @[("1 upgraded from 2 to 3")\as_lua_id!]
                    tree = upgrade(tree, tree.version, get_version!)
        switch tree.type
            when "Action"
                stub = tree.stub
                compile_action = compile_actions[stub]
                if compile_action and not tree.target
                    args = [arg for arg in *tree when type(arg) != "string"]
                    -- Force Lua to avoid tail call optimization for debugging purposes
                    -- TODO: use tail call?
                    ret = compile_action(@, tree, unpack(args))
                    if ret == nil
                        info = debug.getinfo(compile_action, "S")
                        filename = Source\from_string(info.source).filename
                        @compile_error tree,
                            "The compile-time action here (#{stub}) failed to return any value.",
                            "Look at the implementation of (#{stub}) in #{filename}:#{info.linedefined} and make sure it's returning something."
                    if SyntaxTree\is_instance(ret)
                        if ret == tree
                            info = debug.getinfo(compile_action, "S")
                            filename = Source\from_string(info.source).filename
                            @compile_error tree,
                                "The compile-time action here (#{stub}) is producing an endless loop.",
                                "Look at the implementation of (#{stub}) in #{filename}:#{info.linedefined} and make sure it's not just returning the original tree."
                        return @compile(ret, compile_actions)
                    return ret

                lua = LuaCode.Value(tree.source)
                if tree.target -- Method call
                    target_lua = @compile tree.target, compile_actions
                    if tostring(target_lua)\match("^%(.*%)$") or tostring(target_lua)\match("^[_a-zA-Z][_a-zA-Z0-9]*$")
                        lua\append target_lua, ":"
                    else
                        lua\append "(", target_lua, "):"
                lua\append((stub)\as_lua_id!,"(")
                args = {}
                for i, tok in ipairs tree
                    if type(tok) == "string" then continue
                    arg_lua = @compile(tok, compile_actions, true)
                    unless arg_lua.is_value
                        if tok.type == "Block"
                            @compile_error tok,
                                "Can't compile action (#{stub}) with a Block as an argument.",
                                "Maybe there should be a compile-time action with that name that isn't being found?"

                        elseif tok.type == "Action"
                            @compile_error tok,
                                "Can't use this as an argument to (#{stub}), since it's not an expression, it produces: #{tostring(arg_lua)}",
                                "Check the implementation of (#{tok.stub}) to see if it is actually meant to produce an expression."
                        else
                            @compile_error tok,
                                "Can't use this as an argument to (#{stub}), since it's not an expression, it produces: #{tostring(arg_lua)}"
                    insert args, arg_lua
                lua\concat_append args, ", "
                lua\append ")"
                return lua

            when "EscapedNomsu"
                lua = LuaCode.Value tree.source, "SyntaxTree{"
                needs_comma, i = false, 1
                as_lua = (x)->
                    if type(x) == 'number'
                        tostring(x)
                    elseif SyntaxTree\is_instance(x)
                        @compile(x, compile_actions)
                    else x\as_lua!

                for k,v in pairs((SyntaxTree\is_instance(tree[1]) and tree[1].type == "EscapedNomsu" and tree) or tree[1])
                    if needs_comma then lua\append ", "
                    else needs_comma = true
                    if k == i
                        i += 1
                    elseif type(k) == 'string' and match(k,"[_a-zA-Z][_a-zA-Z0-9]*")
                        lua\append(k, "= ")
                    else
                        lua\append("[", as_lua(k), "]= ")
                    if k == "source"
                        lua\append tostring(v)\as_lua!
                    else
                        lua\append as_lua(v)
                lua\append "}"
                return lua
            
            when "Block"
                if not force_value
                    lua = LuaCode(tree.source)
                    lua\concat_append([@compile(line, compile_actions)\as_statements! for line in *tree], "\n")
                    return lua
                else
                    lua = LuaCode.Value(tree.source)
                    values = [@compile(line) for line in *tree]
                    all_values = true
                    for v in *values do all_values and= v.is_value
                    if all_values
                        return values[1] if #values == 1
                        lua\append "("
                        lua\concat_append(values, " and nil or ")
                        lua\append ")"
                    else
                        lua\append("((function()")
                        for i, v in ipairs(values)
                            if v.is_value
                                v = v\as_statements(i == #values and 'return ' or '')
                            lua\append "\n    ", v
                        lua\append("\nend)())")
                    return lua

            when "Text"
                lua = LuaCode.Value(tree.source)
                string_buffer = ""
                for i, bit in ipairs tree
                    if type(bit) == "string"
                        string_buffer ..= bit
                        continue
                    if string_buffer != ""
                        if #lua.bits > 0 then lua\append ".."
                        lua\append string_buffer\as_lua!
                        string_buffer = ""
                    bit_lua = @compile(bit, compile_actions)
                    unless bit_lua.is_value
                        src = '    '..gsub(tostring(@compile(bit, compile_actions)), '\n','\n    ')
                        line = "#{bit.source.filename}:#{Files.get_line_number(Files.read(bit.source.filename), bit.source.start)}"
                        @compile_error bit,
                            "Can't this as a string interpolation value, since it's not an expression."
                    if #lua.bits > 0 then lua\append ".."
                    if bit.type != "Text"
                        bit_lua = LuaCode.Value(bit.source, "stringify(",bit_lua,")")
                    lua\append bit_lua

                if string_buffer ~= "" or #lua.bits == 0
                    if #lua.bits > 0 then lua\append ".."
                    lua\append string_buffer\as_lua!

                if #lua.bits > 1
                    lua\parenthesize!
                return lua

            when "List"
                lua = LuaCode.Value tree.source, "_List{"
                lua\concat_append([@compile(e, compile_actions) for e in *tree], ", ", ",\n  ")
                lua\append "}"
                return lua

            when "Dict"
                lua = LuaCode.Value tree.source, "_Dict{"
                lua\concat_append([@compile(e, compile_actions) for e in *tree], ", ", ",\n  ")
                lua\append "}"
                return lua

            when "DictEntry"
                key, value = tree[1], tree[2]
                key_lua = @compile(key, compile_actions)
                unless key_lua.is_value
                    @compile_error tree[1],
                        "Can't use this as a dict key, since it's not an expression."
                value_lua = value and @compile(value, compile_actions) or LuaCode.Value(key.source, "true")
                unless value_lua.is_value
                    @compile_error tree[2],
                        "Can't use this as a dict value, since it's not an expression."
                key_str = match(tostring(key_lua), [=[^["']([a-zA-Z_][a-zA-Z0-9_]*)['"]$]=])
                return if key_str and key_str\is_lua_id!
                    LuaCode tree.source, key_str,"=",value_lua
                elseif sub(tostring(key_lua),1,1) == "["
                    -- NOTE: this *must* use a space after the [ to avoid freaking out
                    -- Lua's parser if the inner expression is a long string. Lua
                    -- parses x[[[y]]] as x("[y]"), not as x["y"]
                    LuaCode tree.source, "[ ",key_lua,"]=",value_lua
                else
                    LuaCode tree.source, "[",key_lua,"]=",value_lua
            
            when "IndexChain"
                lua = @compile(tree[1], compile_actions)
                unless lua.is_value
                    @compile_error tree[1],
                        "Can't index into this, since it's not an expression."
                first_char = sub(tostring(lua),1,1)
                if first_char == "{" or first_char == '"' or first_char == "["
                    lua\parenthesize!

                for i=2,#tree
                    key = tree[i]
                    key_lua = @compile(key, compile_actions)
                    unless key_lua.is_value
                        @compile_error key,
                            "Can't use this as an index, since it's not an expression."
                    key_lua_str = tostring(key_lua)
                    lua_id = match(key_lua_str, "^['\"]([a-zA-Z_][a-zA-Z0-9_]*)['\"]$")
                    if lua_id and lua_id\is_lua_id!
                        lua\append ".#{lua_id}"
                    elseif sub(key_lua_str,1,1) == '['
                        -- NOTE: this *must* use a space after the [ to avoid freaking out
                        -- Lua's parser if the inner expression is a long string. Lua
                        -- parses x[[[y]]] as x("[y]"), not as x["y"]
                        lua\append "[ ",key_lua," ]"
                    else
                        lua\append "[",key_lua,"]"
                return lua

            when "Number"
                return LuaCode.Value(tree.source, tostring(tree[1]))

            when "Var"
                return LuaCode.Value(tree.source, (tree[1])\as_lua_id!)

            when "FileChunks"
                error("Can't convert FileChunks to a single block of lua, since each chunk's "..
                    "compilation depends on the earlier chunks")
            
            when "Comment"
                -- TODO: implement?
                return LuaCode(tree.source, "")
            
            when "Error"
                error("Can't compile errors")

            else
                error("Unknown type: #{tree.type}")

    .tree_to_inline_nomsu = (tree, parenthesize_blocks=false, check=nil, len=0)=>
        recurse = (tree, nomsu=nil, parenthesize_blocks=false)->
            @tree_to_inline_nomsu(tree, parenthesize_blocks, check, len + (nomsu and #tostring(nomsu) or 0))
        switch tree.type
            when "FileChunks"
                error("Can't inline a FileChunks")
            
            when "Comment"
                -- TODO: implement?
                return NomsuCode(tree.source, "")
            
            when "Error"
                error("Can't compile errors")

            when "Action"
                nomsu = NomsuCode(tree.source)
                if tree.target
                    inline_target = @tree_to_inline_nomsu(tree.target)
                    if tree.target.type == "Action"
                        inline_target\parenthesize!
                    nomsu\append inline_target, "::"
                for i,bit in ipairs tree
                    if type(bit) == "string"
                        clump_words = (type(tree[i-1]) == 'string' and is_operator(bit) != is_operator(tree[i-1]))
                        nomsu\append " " if i > 1 and not clump_words
                        nomsu\append bit
                    else
                        arg_nomsu = recurse(bit, nomsu, parenthesize_blocks or (i == 1 or i < #tree))
                        nomsu\append " " unless arg_nomsu\match("^:") or i == 1
                        arg_nomsu\parenthesize! if bit.type == "Action"
                        nomsu\append arg_nomsu
                    check(len, nomsu, tree) if check
                return nomsu

            when "EscapedNomsu"
                inner_nomsu = recurse(tree[1])
                unless tree[1].type == "List" or tree[1].type == "Dict" or tree[1].type == "Var"
                    inner_nomsu\parenthesize!
                nomsu = NomsuCode(tree.source, "\\", inner_nomsu)
                check(len, nomsu, tree) if check
                return nomsu

            when "Block"
                nomsu = NomsuCode(tree.source, ":")
                check(len, nomsu, tree) if check
                for i,line in ipairs tree
                    nomsu\append(i == 1 and " " or "; ")
                    nomsu\append recurse(line, nomsu, i == 1 or i < #tree)
                    check(len, nomsu, tree) if check
                nomsu\parenthesize! if #tree > 1 or parenthesize_blocks
                return nomsu

            when "Text"
                add_text = (nomsu, tree)->
                    for i, bit in ipairs tree
                        if type(bit) == 'string'
                            escaped = inline_escape(bit)
                            nomsu\append inline_escape(bit)
                        elseif bit.type == "Text"
                            add_text(nomsu, bit)
                        else
                            interp_nomsu = recurse(bit, nomsu)
                            if bit.type != "Var" and bit.type != "List" and bit.type != "Dict"
                                interp_nomsu\parenthesize!
                            elseif bit.type == "Var" and type(tree[i+1]) == 'string' and not match(tree[i+1], "^[ \n\t,.:;#(){}[%]]")
                                interp_nomsu\parenthesize!
                            nomsu\append "\\", interp_nomsu
                        check(len, nomsu, tree) if check
                nomsu = NomsuCode(tree.source)
                add_text(nomsu, tree)
                return NomsuCode(tree.source, '"', nomsu, '"')

            when "List", "Dict"
                nomsu = NomsuCode(tree.source, (tree.type == "List" and "[" or "{"))
                for i, item in ipairs tree
                    nomsu\append ", " if i > 1
                    nomsu\append recurse(item, nomsu)
                    check(len, nomsu, tree) if check
                nomsu\append(tree.type == "List" and "]" or "}")
                return nomsu
            
            when "DictEntry"
                key, value = tree[1], tree[2]
                nomsu = if key.type == "Text" and #key == 1 and is_identifier(key[1])
                    NomsuCode(key.source, key[1])
                else recurse(key)
                nomsu\parenthesize! if key.type == "Action" or key.type == "Block"
                assert(value.type != "Block", "Didn't expect to find a Block as a value in a dict")
                nomsu\append ":"
                if value
                    value_nomsu = recurse(value, nomsu)
                    value_nomsu\parenthesize! if value.type == "Block"
                    nomsu\append value_nomsu
                check(len, nomsu, tree) if check
                return nomsu
            
            when "IndexChain"
                nomsu = NomsuCode(tree.source)
                for i, bit in ipairs tree
                    nomsu\append "." if i > 1
                    local bit_nomsu
                    bit_nomsu = if i > 1 and bit.type == "Text" and #bit == 1 and type(bit[1]) == 'string' and is_identifier(bit[1])
                        bit[1]
                    else recurse(bit, nomsu)
                    assert bit.type != "Block"
                    if bit.type == "Action" or bit.type == "IndexChain" or (bit.type == "Number" and i < #tree)
                        bit_nomsu\parenthesize!
                    nomsu\append bit_nomsu
                    check(len, nomsu, tree) if check
                return nomsu
            
            when "Number"
                return NomsuCode(tree.source, tostring(tree[1]))

            when "Var"
                return NomsuCode(tree.source, "%", tree[1])
            
            else
                error("Unknown type: #{tree.type}")

    .tree_to_nomsu = (tree, pop_comments=nil)=>
        unless pop_comments
            comment_set = {}
            find_comments = (t)->
                if t.comments and t.source.filename == tree.source.filename
                    comment_set[c] = true for c in *t.comments
                find_comments(x) for x in *t when SyntaxTree\is_instance x
            find_comments(tree)
            -- Sort in reversed order so they can be easily popped
            comments = [c for c in pairs comment_set]
            table.sort(comments, (a,b)->(a.source.start > b.source.start))

            pop_comments = (pos, prefix='', suffix='')->
                nomsu = NomsuCode(tree.source)
                for i=#comments,1,-1
                    break if comments[i].source.start > pos
                    comment, comments[i] = comments[i][1], nil
                    nomsu\append("#"..(gsub(comment, "\n", "\n    ")).."\n")
                    if comment\match("^\n.") then nomsu\append("\n") -- for aesthetics
                return '' if #nomsu.bits == 0
                nomsu\prepend(prefix) unless prefix == ''
                nomsu\append(suffix) unless suffix == ''
                return nomsu

        -- For concision:
        recurse = (t, pos)->
            if pos == nil then pos = 0
            if type(pos) != 'number' then pos = #tostring(pos)\match("[ ]*([^\n]*)$")
            space = MAX_LINE - pos
            local inline
            for prefix, nomsu, tree in coroutine.wrap(-> inline = @tree_to_inline_nomsu(t, false, coroutine.yield))
                len = #tostring(nomsu)
                break if prefix+len > MAX_LINE
                break if tree.type == "Block" and (#tree > 1 or len > 20)
                if tree.type == "Text"
                    -- Disallow inline text if it's got newlines between text, e.g. "hello\nworld"
                    check_for_nl = (tree)->
                        found_nl = false
                        for i,b in ipairs tree
                            return true if type(b) != 'string' and b.type == "Text" and check_for_nl(b)
                            b = b\match('^[\n]*(.*)') if i == 1 and type(b) == 'string'
                            found_nl or= type(b) == 'string' and b\match('\n')
                            return true if found_nl and (type(b) != 'string' or b\match('[^\n]'))
                    break if check_for_nl(tree)
            return inline if inline and #tostring(inline) <= space
            indented = @tree_to_nomsu(t, pop_comments, space)
            if t.type == "Action" and not (tree.type == "Block" or tree.type == "FileChunks")
                indented = NomsuCode(t.source, "(..)\n    ", pop_comments(t.source.start), indented)
            return indented

        switch tree.type
            when "FileChunks"
                nomsu = NomsuCode(tree.source, pop_comments(tree.source.start))
                should_clump = (prev_line, line)->
                    if prev_line.type == "Action" and line.type == "Action"
                        if prev_line.stub == "use 1" then return line.stub == "use 1"
                        if prev_line.stub == "test 1" then return true
                        if line.stub == "test 1" then return false
                    return not recurse(prev_line)\is_multiline!
                for chunk_no, chunk in ipairs tree
                    nomsu\append "\n\n#{("~")\rep(80)}\n\n" if chunk_no > 1
                    nomsu\append pop_comments(chunk.source.start)
                    if chunk.type == "Block"
                        for line_no, line in ipairs chunk
                            if line_no > 1
                                if should_clump(chunk[line_no-1], line)
                                    nomsu\append "\n", pop_comments(line.source.start, '\n')
                                else
                                    nomsu\append "\n\n", pop_comments(line.source.start)
                            nomsu\append @tree_to_nomsu(line, pop_comments)
                        nomsu\append pop_comments(chunk.source.stop, '\n')
                    else
                        nomsu\append recurse(chunk)
                nomsu\append pop_comments(tree.source.stop, '\n')
                nomsu\append('\n') unless nomsu\match("\n$")
                return nomsu

            when "Action"
                pos, next_space = tree.source.start, ''
                nomsu = NomsuCode(tree.source, pop_comments(pos))
                if tree.target
                    if tree.target.type == "Block"
                        nomsu\append(recurse(tree.target, #nomsu\match('[^\n]*$')))
                        pos = tree.target.source.stop
                        next_space = inline and "::" or "\n..::"
                    else
                        target_nomsu = recurse(tree.target, #nomsu\match('[^\n]*$'))
                        if tree.target.type == "Action" and not target_nomsu\is_multiline!
                            target_nomsu\parenthesize!
                        nomsu\append target_nomsu
                        pos = tree.target.source.stop
                        next_space = target_nomsu\is_multiline! and "\n..::" or "::"

                for i,bit in ipairs tree
                    if next_space == "\n.."
                        nomsu\append "\n", pop_comments(pos), '..'
                        next_space = ""
                    elseif next_space == " " and nomsu\trailing_line_len! > MAX_LINE
                        nomsu\append " \\\n", pop_comments(pos), '..'
                        next_space = ""

                    if type(bit) == "string"
                        unless type(tree[i-1]) == 'string' and is_operator(tree[i-1]) != is_operator(bit)
                            nomsu\append(next_space)
                        nomsu\append bit
                        next_space = ' '
                    elseif bit.type == "Block"
                        nomsu\append(recurse(bit, #nomsu\match('[^\n]*$')))
                        pos = bit.source.stop
                        next_space = inline and " " or "\n.."
                    else
                        nomsu\append next_space
                        bit_nomsu = recurse(bit, #nomsu\match('[^\n]*$'))
                        if bit.type == "Action" and not bit_nomsu\is_multiline!
                            bit_nomsu\parenthesize!
                        nomsu\append bit_nomsu
                        pos = bit.source.stop
                        next_space = bit_nomsu\is_multiline! and "\n.." or " "

                nomsu\append pop_comments(tree.source.stop, '\n')
                return nomsu

            when "EscapedNomsu"
                val_nomsu = recurse(tree[1], 1)
                if tree[1].type == "Action" and not val_nomsu\is_multiline!
                    val_nomsu\parenthesize!
                return NomsuCode tree.source, "\\", val_nomsu

            when "Block"
                nomsu = NomsuCode(tree.source, pop_comments(tree.source.start))
                for i, line in ipairs tree
                    nomsu\append pop_comments(line.source.start, i > 1 and '\n' or '')
                    line_nomsu = recurse(line)
                    nomsu\append line_nomsu
                    if i < #tree
                        nomsu\append(line_nomsu\match('\n[^\n]*\n') and "\n\n" or "\n")
                nomsu\append pop_comments(tree.source.stop, '\n')
                return NomsuCode(tree.source, ":\n    ", nomsu)

            when "Text"
                -- Multi-line text has more generous wrap margins
                max_line = math.floor(1.5*MAX_LINE)
                add_text = (nomsu, tree)->
                    for i, bit in ipairs tree
                        if type(bit) == 'string'
                            bit = escape(bit)
                            bit_lines = Files.get_lines(bit)
                            for j, line in ipairs bit_lines
                                if j > 1
                                    nomsu\append "\n"
                                elseif #line > 10 and nomsu\trailing_line_len! > max_line
                                    nomsu\append "\\\n.."

                                while #line > 0
                                    space = max_line - nomsu\trailing_line_len!
                                    split = find(line, "[%p%s]", space)
                                    if not split or split > space + 10
                                        split = space + 10
                                    if #line - split < 10
                                        split = #line
                                    bite, line = sub(line, 1, split), sub(line, split+1, -1)
                                    nomsu\append bite
                                    nomsu\append "\\\n.." if #line > 0
                        elseif bit.type == "Text"
                            add_text(nomsu, bit)
                        else
                            nomsu\append "\\"
                            interp_nomsu = recurse(bit, #nomsu\match('[^\n]*$'))
                            unless interp_nomsu\is_multiline!
                                if bit.type == "Var"
                                    if type(tree[i+1]) == 'string' and not match(tree[i+1], "^[ \n\t,.:;#(){}[%]]")
                                        interp_nomsu\parenthesize!
                                elseif bit.type != "List" and bit.type != "Dict"
                                    interp_nomsu\parenthesize!
                            nomsu\append interp_nomsu
                            if interp_nomsu\is_multiline!
                                nomsu\append "\n.."
                nomsu = NomsuCode(tree.source)
                add_text(nomsu, tree)
                return NomsuCode(tree.source, '"\\\n    ..', nomsu, '"')

            when "List", "Dict"
                assert #tree > 0
                nomsu = NomsuCode(tree.source, pop_comments(tree[1].source.start))
                for i, item in ipairs tree
                    nomsu\append(pop_comments(item.source.start)) if nomsu\trailing_line_len! == 0
                    inline_nomsu = @tree_to_inline_nomsu(item)
                    item_nomsu = #tostring(inline_nomsu) <= MAX_LINE and inline_nomsu or recurse(item, #nomsu\match('[^\n]*$'))
                    nomsu\append item_nomsu
                    if i < #tree
                        nomsu\append((item_nomsu\is_multiline! or nomsu\trailing_line_len! + #tostring(item_nomsu) >= MAX_LINE) and '\n' or ', ')
                nomsu\append pop_comments(tree.source.stop, '\n')
                return if tree.type == "List" then
                    NomsuCode(tree.source, "[..]\n    ", nomsu)
                else
                    NomsuCode(tree.source, "{..}\n    ", nomsu)
            
            when "DictEntry"
                key, value = tree[1], tree[2]
                nomsu = if key.type == "Text" and #key == 1 and is_identifier(key[1])
                    NomsuCode(key.source, key[1])
                else @tree_to_inline_nomsu(key)
                nomsu\parenthesize! if key.type == "Action" or key.type == "Block"
                nomsu\append ": ", recurse(value, #tostring(nomsu))
                return nomsu
            
            when "IndexChain", "Number", "Var", "Comment", "Error"
                return @tree_to_inline_nomsu tree
            
            else
                error("Unknown type: #{tree.type}")

return NomsuCompiler