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)
{
    ret alt 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.
            alt mac.node {
              mac_invoc(pth, args, body) {
                assert (vec::len(pth.idents) > 0u);
                let extname = pth.idents[0];
                alt 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.ident, 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);
                let extname = pth.idents[0];
                alt exts.find(*extname) {
                  none {
                    cx.span_fatal(pth.span,
                                  #fmt["macro undefined: '%s'", *extname])
                  }
                  some(expr_tt({expander: exp, span: exp_sp})) {
                    let expanded = alt 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 = alt attr.node.value.node {
              ast::meta_word(n) { n }
              ast::meta_name_value(n, _) { n }
              ast::meta_list(n, _) { n }
            };
            alt 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)
              }
            }
        }
    };

    ret {items: new_items with module};
}

// Support for item-position macro invocations, exactly the same
// logic as for expression-position macro invocations.
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 = alt it.node {
      ast::item_mod(_) | ast::item_foreign_mod(_) {true}
      _ {false}
    };
    let maybe_it = alt it.node {
      ast::item_mac(*) {
        expand_item_mac(exts, cx, it, fld)
      }
      _ { some(it) }
    };

    alt maybe_it {
      some(it) {
        if is_mod { cx.mod_push(it.ident); }
        let ret_val = orig(it, fld);
        if is_mod { cx.mod_pop(); }
        ret ret_val;
      }
      none { ret none; }
    }
}

fn expand_item_mac(exts: hashmap<~str, syntax_extension>,
                   cx: ext_ctxt, &&it: @ast::item,
                   fld: ast_fold) -> option<@ast::item> {
    alt it.node {
      item_mac({node: mac_invoc_tt(pth, tts), span}) {
        let extname = pth.idents[0];
        alt 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 = alt expanded {
              mr_item(it) { fld.fold_item(it) }
              mr_expr(e) { cx.span_fatal(pth.span,
                                         ~"expr macro in item position: " +
                                         *extname) }
              mr_def(mdef) {
                exts.insert(*mdef.ident, mdef.ext);
                none
              }
            };
            cx.bt_pop();
            ret 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 */
    ret {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 {
    ret
~"{
    #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);
    ret 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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