From bdd0c9387bb10e0db01c00dcd47ea3e6bc343e45 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Fri, 2 Mar 2012 14:36:22 -0800
Subject: [PATCH] get new decorator extensions working

---
 src/comp/syntax/ext/auto_serialize.rs | 388 ++++++++++++++++++++++++++
 src/libcore/vec.rs                    |   8 +
 src/rustc/rustc.rc                    |   1 +
 src/rustc/syntax/ext/base.rs          |   3 +
 src/rustc/syntax/ext/expand.rs        |  48 ++++
 src/rustc/syntax/fold.rs              |   1 +
 6 files changed, 449 insertions(+)
 create mode 100644 src/comp/syntax/ext/auto_serialize.rs

diff --git a/src/comp/syntax/ext/auto_serialize.rs b/src/comp/syntax/ext/auto_serialize.rs
new file mode 100644
index 00000000000..0f4ad795b89
--- /dev/null
+++ b/src/comp/syntax/ext/auto_serialize.rs
@@ -0,0 +1,388 @@
+/*
+
+The compiler code necessary to implement the #[auto_serialize]
+extension.  The idea here is that type-defining items may be tagged
+with #[auto_serialize], which will cause us to generate a little
+companion module with the same name as the item.
+
+For example, a type like:
+
+    type node_id = uint;
+
+would generate a companion module like:
+
+    mod node_id {
+        use std;
+        import std::serialization::serializer;
+        import std::serialization::deserializer;
+        fn serialize<S: serializer>(s: S, v: node_id) {
+             s.emit_uint(v);
+        }
+        fn deserializer<D: deserializer>(d: D) -> node_id {
+             d.read_uint()
+        }
+    }
+
+Other interesting scenarios are whe the item has type parameters or
+references other non-built-in types.  A type definition like:
+
+    type spanned<T> = {node: T, span: span};
+
+would yield a helper module like:
+
+    mod spanned {
+        use std;
+        import std::serialization::serializer;
+        import std::serialization::deserializer;
+        fn serialize<S: serializer,T>(s: S, t: fn(T), v: spanned<T>) {
+             s.emit_rec(2u) {||
+                 s.emit_rec_field("node", 0u) {||
+                     t(s.node);
+                 };
+                 s.emit_rec_field("span", 1u) {||
+                     span::serialize(s, s.span);
+                 };
+             }
+        }
+        fn deserializer<D: deserializer>(d: D, t: fn() -> T) -> node_id {
+             d.read_rec(2u) {||
+                 {node: d.read_rec_field("node", 0u, t),
+                  span: d.read_rec_field("span", 1u) {||span::deserialize(d)}}
+             }
+        }
+    }
+
+In general, the code to serialize an instance `v` of a non-built-in
+type a::b::c<T0,...,Tn> looks like:
+
+    a::b::c::serialize(s, {|v| c_T0}, ..., {|v| c_Tn}, v)
+
+where `c_Ti` is the code to serialize an instance `v` of the type
+`Ti`.
+
+Similarly, the code to deserialize an instance of a non-built-in type
+`a::b::c<T0,...,Tn>` using the deserializer `d` looks like:
+
+    a::b::c::deserialize(d, {|| c_T0}, ..., {|| c_Tn})
+
+where `c_Ti` is the code to deserialize an instance of `Ti` using the
+deserializer `d`.
+
+TODO--Hygiene. Search for "__" strings.
+
+*/
+import base::*;
+import driver::session::session;
+import codemap::span;
+import std::map;
+
+export expand_auto_serialize;
+
+enum ser_cx = {
+    ext_cx: ext_ctxt,
+    tps: map::map<str, fn@(@ast::expr) -> [@ast::stmt]>
+};
+
+fn expand_auto_serialize(cx: ext_ctxt,
+                         span: span,
+                         mitem: ast::meta_item,
+                         in_items: [@ast::item]) -> [@ast::item] {
+    vec::flat_map(in_items) {|in_item|
+        alt in_item.node {
+          ast::item_ty(ty, tps) {
+            [in_item, ty_module(cx, in_item.ident, ty, tps)]
+          }
+
+          ast::item_enum(variants, tps) {
+            [in_item, enum_module(cx, in_item.ident, variants, tps)]
+          }
+
+          _ {
+            cx.session().span_err(span, "#[auto_serialize] can only be \
+                                         applied to type and enum \
+                                         definitions");
+            [in_item]
+          }
+        }
+    }
+}
+
+impl helpers for ser_cx {
+    fn session() -> session { self.ext_cx.session() }
+
+    fn next_id() -> ast::node_id { self.session().next_node_id() }
+
+    fn path(span: span, strs: [str]) -> @ast::path {
+        @{node: {global: false,
+                 idents: strs + ["serialize"],
+                 types: []},
+          span: span}
+    }
+
+    fn expr(span: span, node: ast::expr_) -> @ast::expr {
+        @{id: self.next_id(), node: node, span: span}
+    }
+
+    fn ty_path(span: span, strs: [str]) -> @ast::ty {
+        @{node: ast::ty_path(self.path(span, strs), self.next_id()),
+          span: span}
+    }
+
+    fn var_ref(span: span, name: str) -> @ast::expr {
+        self.expr(span, ast::expr_path(self.path(span, [name])))
+    }
+
+    fn blk(span: span, stmts: [@ast::stmt]) -> ast::blk {
+        {node: {view_items: [],
+                stmts: stmts,
+                expr: none,
+                id: self.next_id(),
+                rules: ast::default_blk},
+         span: span}
+    }
+
+    fn binder_pat(span: span, nm: str) -> @ast::pat {
+        let path = @{node: {global: false,
+                            idents: [nm],
+                            types: []},
+                     span: span};
+        @{id: self.next_id(),
+          node: ast::pat_ident(path, none),
+          span: span}
+    }
+
+    fn stmt(expr: @ast::expr) -> @ast::stmt {
+        @{node: ast::stmt_semi(expr, self.next_id()),
+          span: expr.span}
+    }
+
+    fn alt_stmt(arms: [ast::arm], span: span, -v: @ast::expr) -> @ast::stmt {
+        self.stmt(
+            self.expr(
+                span,
+                ast::expr_alt(v, arms, ast::alt_exhaustive)))
+    }
+
+    fn clone(v: @ast::expr) -> @ast::expr {
+        let fld = fold::make_fold({
+            new_id: {|_id| self.next_id()}
+            with *fold::default_ast_fold()
+        });
+        fld.fold_expr(v)
+    }
+
+    fn clone_ty_param(v: ast::ty_param) -> ast::ty_param {
+        let fld = fold::make_fold({
+            new_id: {|_id| self.next_id()}
+            with *fold::default_ast_fold()
+        });
+        fold::fold_ty_param(v, fld)
+    }
+
+    fn at(span: span, expr: @ast::expr) -> @ast::expr {
+        fn repl_sp(old_span: span, repl_span: span, with_span: span) -> span {
+            if old_span == repl_span {
+                with_span
+            } else {
+                old_span
+            }
+        }
+
+        let fld = fold::make_fold({
+            new_span: repl_sp(_, ast_util::dummy_sp(), span)
+            with *fold::default_ast_fold()
+        });
+
+        fld.fold_expr(expr)
+    }
+}
+
+fn serialize_path(cx: ser_cx, path: @ast::path, -s: @ast::expr, -v: @ast::expr)
+    -> [@ast::stmt] {
+    let ext_cx = cx.ext_cx;
+
+    // We want to take a path like a::b::c<...> and generate a call
+    // like a::b::c::serialize(s, ...), as described above.
+
+    let callee =
+        cx.expr(
+            path.span,
+            ast::expr_path(
+                cx.path(path.span, path.node.idents + ["serialize"])));
+
+    let ty_args = vec::map(path.node.types) {|ty|
+        let sv = serialize_ty(cx, ty, s, #ast(expr){"__v"});
+        cx.at(ty.span, #ast(expr){"{|__v| $(sv)}"})
+    };
+
+    [cx.stmt(
+        cx.expr(
+            path.span,
+            ast::expr_call(callee, [s] + ty_args + [v], false)))]
+}
+
+fn serialize_variant(cx: ser_cx,
+                     tys: [@ast::ty],
+                     span: span,
+                     -s: @ast::expr,
+                     pfn: fn([@ast::pat]) -> ast::pat_) -> ast::arm {
+    let vnames = vec::init_fn(vec::len(tys)) {|i| #fmt["__v%u", i]};
+    let pats = vec::init_fn(vec::len(tys)) {|i|
+        cx.binder_pat(tys[i].span, vnames[i])
+    };
+    let pat: @ast::pat = @{id: cx.next_id(), node: pfn(pats), span: span};
+    let stmts = vec::init_fn(vec::len(tys)) {|i|
+        let v = cx.var_ref(span, vnames[i]);
+        serialize_ty(cx, tys[i], cx.clone(s), v)
+    };
+    {pats: [pat], guard: none, body: cx.blk(span, vec::concat(stmts))}
+}
+
+fn serialize_ty(cx: ser_cx, ty: @ast::ty, -s: @ast::expr, -v: @ast::expr)
+    -> [@ast::stmt] {
+    let ext_cx = cx.ext_cx;
+
+    alt ty.node {
+      ast::ty_nil | ast::ty_bot {
+        []
+      }
+
+      ast::ty_box(mt) |
+      ast::ty_uniq(mt) |
+      ast::ty_ptr(mt) {
+        serialize_ty(cx, mt.ty, s, #ast(expr){"*$(v)"})
+      }
+
+      ast::ty_rec(flds) {
+        vec::flat_map(flds) {|fld|
+            let vf = cx.expr(
+                fld.span,
+                ast::expr_field(cx.clone(v), fld.node.ident, []));
+            serialize_ty(cx, fld.node.mt.ty, cx.clone(s), vf)
+        }
+      }
+
+      ast::ty_fn(_, _) {
+        cx.session().span_err(
+            ty.span, #fmt["Cannot serialize function types"]);
+        []
+      }
+
+      ast::ty_tup(tys) {
+        // Generate code like
+        //
+        // alt v {
+        //    (v1, v2, v3) {
+        //       .. serialize v1, v2, v3 ..
+        //    }
+        // };
+
+        let arms = [
+            serialize_variant(cx, tys, ty.span, s,
+                              {|pats| ast::pat_tup(pats)})
+        ];
+        [cx.alt_stmt(arms, ty.span, v)]
+      }
+
+      ast::ty_path(path, _) {
+        if vec::len(path.node.idents) == 1u &&
+            vec::is_empty(path.node.types) {
+            let ident = path.node.idents[0];
+
+            alt cx.tps.find(ident) {
+              some(f) { f(v) }
+              none { serialize_path(cx, path, s, v) }
+            }
+        } else {
+            serialize_path(cx, path, s, v)
+        }
+      }
+
+      ast::ty_constr(ty, _) {
+        serialize_ty(cx, ty, s, v)
+      }
+
+      ast::ty_mac(_) {
+        cx.session().span_err(
+            ty.span, #fmt["Cannot serialize macro types"]);
+        []
+      }
+
+      ast::ty_infer {
+        cx.session().span_err(
+            ty.span, #fmt["Cannot serialize inferred types"]);
+        []
+      }
+
+      ast::ty_vec(mt) {
+        let ser_e =
+            cx.expr(
+                ty.span,
+                expr_block(
+                    cx.blk(
+                        ty.span,
+                        serialize_ty(
+                            cx, mt.ty,
+                            cx.clone(s),
+                            cx.at(
+                                ty.span,
+                                #ast(expr){__e})))));
+        [#ast(stmt){ $(s).emit_from_vec($(v), {|__e| $(ser_e) }) }]
+      }
+    }
+}
+
+fn ty_module(ext_cx: ext_ctxt, name: str, -ty: @ast::ty, tps: [ast::ty_param])
+    -> @ast::item {
+
+    let cx = ser_cx({ext_cx: ext_cx, tps: map::new_str_hash()});
+
+    let ser_inputs: [ast::arg] =
+        [{mode: ast::expl(ast::by_ref),
+          ty: cx.ty_path(ty.span, ["__S"]),
+          ident: "__s",
+          id: cx.next_id()},
+         {mode: ast::expl(ast::by_ref),
+          ty: ty,
+          ident: "__v",
+          id: cx.next_id()}] +
+        vec::map(tps, {|tp|
+            {mode: ast::expl(ast::by_ref),
+             ty: cx.ty_path(ty.span, [tp.ident]),
+             ident: "__v",
+             id: cx.next_id()}});
+
+    let ser_bnds = @[ast::bound_iface(cx.ty_path(ty.span,
+                                                 ["__std", "serialization",
+                                                  "serializer"]))];
+    let ser_tps: [ast::ty_param] =
+        [{ident: "__S",
+          id: cx.next_id(),
+          bounds: ser_bnds}] +
+        vec::map(tps) {|tp| cx.clone_ty_param(tp) };
+
+    let ser_output: @ast::ty = @{node: ast::ty_nil,
+                                 span: ty.span};
+
+    let ser_blk = cx.blk(ty.span,
+                         serialize_ty(cx, ty,
+                                      #ast(expr){"__s"}, #ast(expr){"__v"}));
+
+    @{ident: "serialize",
+      attrs: [],
+      id: cx.next_id(),
+      node: ast::item_fn({inputs: ser_inputs,
+                          output: ser_output,
+                          purity: ast::impure_fn,
+                          cf: ast::return_val,
+                          constraints: []},
+                         ser_tps,
+                         ser_blk),
+      span: ty.span}
+}
+
+fn enum_module(cx: ext_ctxt, name: str,
+               variants: [ast::variant], tps: [ast::ty_param])
+    -> @ast::item {
+
+}
\ No newline at end of file
diff --git a/src/libcore/vec.rs b/src/libcore/vec.rs
index 92b22b7850a..663bc20001b 100644
--- a/src/libcore/vec.rs
+++ b/src/libcore/vec.rs
@@ -405,7 +405,15 @@ fn map<T, U>(v: [T], f: fn(T) -> U) -> [U] {
     ret result;
 }
 
+fn flat_map<T, U>(v: [T], f: fn(T) -> [U]) -> [U] {
+    let result = [];
+    for elem: T in v { result += f(elem); }
+    ret result;
+}
+
 #[doc = "
+Function: map2
+
 Apply a function to each pair of elements and return the results
 "]
 fn map2<T: copy, U: copy, V>(v0: [const T], v1: [const U],
diff --git a/src/rustc/rustc.rc b/src/rustc/rustc.rc
index 4a512e059c1..516159ee8f6 100644
--- a/src/rustc/rustc.rc
+++ b/src/rustc/rustc.rc
@@ -87,6 +87,7 @@ mod syntax {
         mod concat_idents;
         mod ident_to_str;
         mod log_syntax;
+        mod auto_serialize;
     }
     mod print {
         mod pprust;
diff --git a/src/rustc/syntax/ext/base.rs b/src/rustc/syntax/ext/base.rs
index d59591d849a..721f059ee35 100644
--- a/src/rustc/syntax/ext/base.rs
+++ b/src/rustc/syntax/ext/base.rs
@@ -11,10 +11,13 @@ type syntax_expander = {
 type macro_def = {ident: str, ext: syntax_extension};
 type macro_definer =
     fn@(ext_ctxt, span, ast::mac_arg, ast::mac_body) -> macro_def;
+type item_decorator =
+    fn@(ext_ctxt, span, ast::meta_item, [@ast::item]) -> [@ast::item];
 
 enum syntax_extension {
     normal(syntax_expander),
     macro_defining(macro_definer),
+    item_decorator(item_decorator),
 }
 
 // A temporary hard-coded map of methods for expanding syntax extension
diff --git a/src/rustc/syntax/ext/expand.rs b/src/rustc/syntax/ext/expand.rs
index 104f49aebac..8384f7a8873 100644
--- a/src/rustc/syntax/ext/expand.rs
+++ b/src/rustc/syntax/ext/expand.rs
@@ -1,13 +1,17 @@
 import driver::session;
+import driver::session::session;
 
 import std::map::hashmap;
 
+import front::attr;
+
 import syntax::ast::{crate, expr_, expr_mac, mac_invoc};
 import syntax::fold::*;
 import syntax::ext::base::*;
 import syntax::ext::qquote::{qq_helper};
 import syntax::parse::parser::parse_expr_from_source_str;
 
+
 import codemap::{span, expanded_from};
 
 fn expand_expr(exts: hashmap<str, syntax_extension>, cx: ext_ctxt,
@@ -26,6 +30,11 @@ fn expand_expr(exts: hashmap<str, syntax_extension>, cx: ext_ctxt,
                     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, pth.span, args, body);
 
@@ -52,6 +61,44 @@ fn expand_expr(exts: hashmap<str, syntax_extension>, cx: ext_ctxt,
         };
 }
 
+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 = vec::flat_map(module.items) {|item|
+        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 { items }
+
+              some(normal(_)) | some(macro_defining(_)) {
+                cx.span_err(
+                    attr.span,
+                    #fmt["%s cannot be used as a decorator", mname]);
+                items
+              }
+
+              some(item_decorator(dec_fn)) {
+                dec_fn(cx, attr.span, attr.node.value, items)
+              }
+            }
+        }
+    };
+
+    ret {items: new_items with module};
+}
+
 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()};
@@ -78,6 +125,7 @@ fn expand_crate(sess: session::session, c: @crate) -> @crate {
     let cx: ext_ctxt = mk_ctxt(sess);
     let f_pre =
         {fold_expr: bind expand_expr(exts, cx, _, _, _, afp.fold_expr),
+         fold_mod: bind expand_mod_items(exts, cx, _, _, afp.fold_mod),
          new_span: bind new_span(cx, _)
             with *afp};
     let f = make_fold(f_pre);
diff --git a/src/rustc/syntax/fold.rs b/src/rustc/syntax/fold.rs
index f24f339590d..9e6ee76db9b 100644
--- a/src/rustc/syntax/fold.rs
+++ b/src/rustc/syntax/fold.rs
@@ -13,6 +13,7 @@ export noop_fold_mod;
 export noop_fold_ty;
 export noop_fold_block;
 export wrap;
+export fold_ty_param;
 
 type ast_fold = @mutable a_f;