rust/src/libsyntax/ext/expand.rs

import std::map::hashmap;

import ast::{crate, expr_, expr_mac, mac_invoc, mac_invoc_tt,
             tt_delim, tt_tok, item_mac};
import fold::*;
import ext::base::*;
import ext::qquote::{qq_helper};
import parse::{parser, parse_expr_from_source_str, new_parser_from_tt};


import codemap::{span, expanded_from};

fn expand_expr(exts: hashmap<~str, syntax_extension>, cx: ext_ctxt,
               e: expr_, s: span, fld: ast_fold,
               orig: fn@(expr_, span, ast_fold) -> (expr_, span))
    -> (expr_, span)
{
    return match e {
      // expr_mac should really be expr_ext or something; it's the
      // entry-point for all syntax extensions.
          expr_mac(mac) => {

            // Old-style macros, for compatibility, will erase this whole
            // block once we've transitioned.
            match mac.node {
              mac_invoc(pth, args, body) => {
                assert (vec::len(pth.idents) > 0u);
                /* using idents and token::special_idents would make the
                the macro names be hygienic */
                let extname = cx.parse_sess().interner.get(pth.idents[0]);
                match exts.find(*extname) {
                  None => {
                    cx.span_fatal(pth.span,
                                  fmt!("macro undefined: '%s'", *extname))
                  }
                  Some(item_decorator(_)) => {
                    cx.span_fatal(
                        pth.span,
                        fmt!("%s can only be used as a decorator", *extname));
                  }
                  Some(normal({expander: exp, span: exp_sp})) => {
                    let expanded = exp(cx, mac.span, args, body);

                    cx.bt_push(expanded_from({call_site: s,
                                callie: {name: *extname, span: exp_sp}}));
                    //keep going, outside-in
                    let fully_expanded = fld.fold_expr(expanded).node;
                    cx.bt_pop();

                    (fully_expanded, s)
                  }
                  Some(macro_defining(ext)) => {
                    let named_extension = ext(cx, mac.span, args, body);
                    exts.insert(named_extension.name, named_extension.ext);
                    (ast::expr_rec(~[], None), s)
                  }
                  Some(expr_tt(_)) => {
                    cx.span_fatal(pth.span,
                                  fmt!("this tt-style macro should be \
                                        invoked '%s!(...)'", *extname))
                  }
                  Some(item_tt(*)) => {
                    cx.span_fatal(pth.span,
                                  ~"cannot use item macros in this context");
                  }
                }
              }

              // Token-tree macros, these will be the only case when we're
              // finished transitioning.
              mac_invoc_tt(pth, tts) => {
                assert (vec::len(pth.idents) == 1u);
                /* using idents and token::special_idents would make the
                the macro names be hygienic */
                let extname = cx.parse_sess().interner.get(pth.idents[0]);
                match exts.find(*extname) {
                  None => {
                    cx.span_fatal(pth.span,
                                  fmt!("macro undefined: '%s'", *extname))
                  }
                  Some(expr_tt({expander: exp, span: exp_sp})) => {
                    let expanded = match exp(cx, mac.span, tts) {
                      mr_expr(e) => e,
                      _ => cx.span_fatal(
                          pth.span, fmt!("non-expr macro in expr pos: %s",
                                         *extname))
                    };

                    cx.bt_push(expanded_from({call_site: s,
                                callie: {name: *extname, span: exp_sp}}));
                    //keep going, outside-in
                    let fully_expanded = fld.fold_expr(expanded).node;
                    cx.bt_pop();

                    (fully_expanded, s)
                  }
                  Some(normal({expander: exp, span: exp_sp})) => {
                    //convert the new-style invoc for the old-style macro
                    let arg = base::tt_args_to_original_flavor(cx, pth.span,
                                                               tts);
                    let expanded = exp(cx, mac.span, arg, None);

                    cx.bt_push(expanded_from({call_site: s,
                                callie: {name: *extname, span: exp_sp}}));
                    //keep going, outside-in
                    let fully_expanded = fld.fold_expr(expanded).node;
                    cx.bt_pop();

                    (fully_expanded, s)
                  }
                  _ => {
                    cx.span_fatal(pth.span,
                                  fmt!("'%s' is not a tt-style macro",
                                       *extname))
                  }

                }
              }
              _ => cx.span_bug(mac.span, ~"naked syntactic bit")
            }
          }
          _ => orig(e, s, fld)
        };
}

// This is a secondary mechanism for invoking syntax extensions on items:
// "decorator" attributes, such as #[auto_serialize]. These are invoked by an
// attribute prefixing an item, and are interpreted by feeding the item
// through the named attribute _as a syntax extension_ and splicing in the
// resulting item vec into place in favour of the decorator. Note that
// these do _not_ work for macro extensions, just item_decorator ones.
//
// NB: there is some redundancy between this and expand_item, below, and
// they might benefit from some amount of semantic and language-UI merger.
fn expand_mod_items(exts: hashmap<~str, syntax_extension>, cx: ext_ctxt,
                    module_: ast::_mod, fld: ast_fold,
                    orig: fn@(ast::_mod, ast_fold) -> ast::_mod)
    -> ast::_mod
{
    // Fold the contents first:
    let module_ = orig(module_, fld);

    // For each item, look through the attributes.  If any of them are
    // decorated with "item decorators", then use that function to transform
    // the item into a new set of items.
    let new_items = do vec::flat_map(module_.items) |item| {
        do vec::foldr(item.attrs, ~[item]) |attr, items| {
            let mname = match attr.node.value.node {
              ast::meta_word(n) => n,
              ast::meta_name_value(n, _) => n,
              ast::meta_list(n, _) => n
            };
            match exts.find(mname) {
              None | Some(normal(_)) | Some(macro_defining(_))
              | Some(expr_tt(_)) | Some(item_tt(*)) => items,
              Some(item_decorator(dec_fn)) => {
                dec_fn(cx, attr.span, attr.node.value, items)
              }
            }
        }
    };

    return {items: new_items with module_};
}


// When we enter a module, record it, for the sake of `module!`
fn expand_item(exts: hashmap<~str, syntax_extension>,
               cx: ext_ctxt, &&it: @ast::item, fld: ast_fold,
               orig: fn@(&&@ast::item, ast_fold) -> Option<@ast::item>)
    -> Option<@ast::item>
{
    let is_mod = match it.node {
      ast::item_mod(_) | ast::item_foreign_mod(_) => true,
      _ => false
    };
    let maybe_it = match it.node {
      ast::item_mac(*) => expand_item_mac(exts, cx, it, fld),
      _ => Some(it)
    };

    match maybe_it {
      Some(it) => {
        if is_mod { cx.mod_push(it.ident); }
        let ret_val = orig(it, fld);
        if is_mod { cx.mod_pop(); }
        return ret_val;
      }
      None => return None
    }
}


// Support for item-position macro invocations, exactly the same
// logic as for expression-position macro invocations.
fn expand_item_mac(exts: hashmap<~str, syntax_extension>,
                   cx: ext_ctxt, &&it: @ast::item,
                   fld: ast_fold) -> Option<@ast::item> {
    match it.node {
      item_mac({node: mac_invoc_tt(pth, tts), _}) => {
        let extname = cx.parse_sess().interner.get(pth.idents[0]);
        match exts.find(*extname) {
          None => {
            cx.span_fatal(pth.span,
                          fmt!("macro undefined: '%s'", *extname))
          }
          Some(item_tt(expand)) => {
            let expanded = expand.expander(cx, it.span, it.ident, tts);
            cx.bt_push(expanded_from({call_site: it.span,
                                      callie: {name: *extname,
                                               span: expand.span}}));
            let maybe_it = match expanded {
              mr_item(it) => fld.fold_item(it),
              mr_expr(_) => cx.span_fatal(pth.span,
                                         ~"expr macro in item position: " +
                                         *extname),
              mr_def(mdef) => {
                exts.insert(mdef.name, mdef.ext);
                None
              }
            };
            cx.bt_pop();
            return maybe_it
          }
          _ => cx.span_fatal(it.span,
                            fmt!("%s is not a legal here", *extname))
        }
      }
      _ => cx.span_bug(it.span, ~"invalid item macro invocation")
    }
}

fn new_span(cx: ext_ctxt, sp: span) -> span {
    /* this discards information in the case of macro-defining macros */
    return {lo: sp.lo, hi: sp.hi, expn_info: cx.backtrace()};
}

// FIXME (#2247): this is a terrible kludge to inject some macros into
// the default compilation environment. When the macro-definition system
// is substantially more mature, these should move from here, into a
// compiled part of libcore at very least.

fn core_macros() -> ~str {
    return
~"{
    #macro[[#error[f, ...], log(core::error, #fmt[f, ...])]];
    #macro[[#warn[f, ...], log(core::warn, #fmt[f, ...])]];
    #macro[[#info[f, ...], log(core::info, #fmt[f, ...])]];
    #macro[[#debug[f, ...], log(core::debug, #fmt[f, ...])]];
}";
}

fn expand_crate(parse_sess: parse::parse_sess,
                cfg: ast::crate_cfg, c: @crate) -> @crate {
    let exts = syntax_expander_table();
    let afp = default_ast_fold();
    let cx: ext_ctxt = mk_ctxt(parse_sess, cfg);
    let f_pre =
        @{fold_expr: |a,b,c| expand_expr(exts, cx, a, b, c, afp.fold_expr),
          fold_mod: |a,b| expand_mod_items(exts, cx, a, b, afp.fold_mod),
          fold_item: |a,b| expand_item(exts, cx, a, b, afp.fold_item),
          new_span: |a|new_span(cx, a)
          with *afp};
    let f = make_fold(f_pre);
    let cm = parse_expr_from_source_str(~"<core-macros>",
                                        @core_macros(),
                                        cfg,
                                        parse_sess);

    // This is run for its side-effects on the expander env,
    // as it registers all the core macros as expanders.
    f.fold_expr(cm);

    let res = @f.fold_crate(*c);
    return res;
}
// Local Variables:
// mode: rust
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// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
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