From a7aecc46a517c4cac0a63ffcdb2e87ebff77e281 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Mon, 19 Nov 2012 18:05:50 -0800
Subject: [PATCH] rustc: Implement "deriving" for monomorphic structs via a
 syntax extension. r=brson

---
 src/libsyntax/ext/base.rs                     |   3 +
 src/libsyntax/ext/build.rs                    |  20 +
 src/libsyntax/ext/deriving.rs                 | 394 ++++++++++++++++++
 src/libsyntax/syntax.rc                       |   1 +
 .../run-pass/deriving-via-extension-c-enum.rs |  16 +
 .../run-pass/deriving-via-extension-struct.rs |  16 +
 6 files changed, 450 insertions(+)
 create mode 100644 src/libsyntax/ext/deriving.rs
 create mode 100644 src/test/run-pass/deriving-via-extension-c-enum.rs
 create mode 100644 src/test/run-pass/deriving-via-extension-struct.rs

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index c4611074b14..ba5d34bfdb4 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -97,6 +97,9 @@ fn syntax_expander_table() -> HashMap<~str, syntax_extension> {
                                 ext::log_syntax::expand_syntax_ext));
     syntax_expanders.insert(~"ast",
                             builtin(ext::qquote::expand_ast));
+    syntax_expanders.insert(~"deriving_eq",
+                            item_decorator(
+                                ext::deriving::expand_deriving_eq));
 
     // Quasi-quoting expanders
     syntax_expanders.insert(~"quote_tokens",
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 10f853495e3..856cc0884ac 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -136,9 +136,29 @@ fn mk_block(cx: ext_ctxt, sp: span,
                span: sp };
     mk_expr(cx, sp, ast::expr_block(blk))
 }
+fn mk_simple_block(cx: ext_ctxt, span: span, expr: @ast::expr) -> ast::blk {
+    let block = {
+        view_items: ~[],
+        stmts: ~[],
+        expr: Some(expr),
+        id: cx.next_id(),
+        rules: ast::default_blk
+    };
+    { node: move block, span: span }
+}
 fn mk_copy(cx: ext_ctxt, sp: span, e: @ast::expr) -> @ast::expr {
     mk_expr(cx, sp, ast::expr_copy(e))
 }
 fn mk_managed(cx: ext_ctxt, sp: span, e: @ast::expr) -> @ast::expr {
     mk_expr(cx, sp, ast::expr_unary(ast::box(ast::m_imm), e))
 }
+fn mk_pat_ident(cx: ext_ctxt, span: span, ident: ast::ident) -> @ast::pat {
+    let path = build::mk_raw_path(span, ~[ ident ]);
+    let pat = ast::pat_ident(ast::bind_by_value, path, None);
+    @{ id: cx.next_id(), node: move pat, span: span }
+}
+fn mk_bool(cx: ext_ctxt, span: span, value: bool) -> @ast::expr {
+    let lit_expr = ast::expr_lit(@{ node: ast::lit_bool(value), span: span });
+    build::mk_expr(cx, span, move lit_expr)
+}
+
diff --git a/src/libsyntax/ext/deriving.rs b/src/libsyntax/ext/deriving.rs
new file mode 100644
index 00000000000..ab0361e88ba
--- /dev/null
+++ b/src/libsyntax/ext/deriving.rs
@@ -0,0 +1,394 @@
+/// The compiler code necessary to implement the #[deriving_eq] and
+/// #[deriving_ord] extensions.
+
+use ast::{and, bind_by_value, binop, blk, default_blk, deref, enum_def, expr};
+use ast::{expr_, expr_addr_of, expr_binary, expr_call, expr_field, expr_lit};
+use ast::{expr_match, expr_path, expr_unary, ident, infer, item, item_};
+use ast::{item_class, item_enum, item_impl, lit_bool, m_imm, meta_item};
+use ast::{method, named_field, or, pat, pat_ident, pat_wild, path, public};
+use ast::{pure_fn, re_anon, return_val, struct_def, sty_region, ty_path};
+use ast::{ty_rptr, unnamed_field};
+use base::ext_ctxt;
+use codemap::span;
+use parse::token::special_idents::clownshoes_extensions;
+
+enum Junction {
+    Conjunction,
+    Disjunction,
+}
+
+impl Junction {
+    fn to_binop(self) -> binop {
+        match self {
+            Conjunction => and,
+            Disjunction => or,
+        }
+    }
+}
+
+pub fn expand_deriving_eq(cx: ext_ctxt,
+                          span: span,
+                          _mitem: meta_item,
+                          in_items: ~[@item])
+                       -> ~[@item] {
+    let result = dvec::DVec();
+    for in_items.each |item| {
+        result.push(copy *item);
+        match item.node {
+            item_class(struct_def, _) => {
+                result.push(expand_deriving_struct_def(cx,
+                                                       span,
+                                                       struct_def,
+                                                       item.ident));
+            }
+            item_enum(ref enum_definition, _) => {
+                result.push(expand_deriving_enum_def(cx,
+                                                     span,
+                                                     enum_definition,
+                                                     item.ident));
+            }
+            _ => result.push(copy *item)    // XXX: Don't copy.
+        }
+    }
+    dvec::unwrap(move result)
+}
+
+fn create_impl_item(cx: ext_ctxt, span: span, +item: item_) -> @item {
+    @{
+        ident: clownshoes_extensions,
+        attrs: ~[],
+        id: cx.next_id(),
+        node: move item,
+        vis: ast::public,
+        span: span,
+    }
+}
+
+/// Creates a method from the given expression, the signature of which
+/// conforms to the `eq` or `ne` method.
+fn create_method(cx: ext_ctxt,
+                 span: span,
+                 method_ident: ident,
+                 type_ident: ident,
+                 body: @expr)
+              -> @method {
+    // Create the type of the `other` parameter.
+    let arg_path_type = build::mk_raw_path(span, ~[ type_ident ]);
+    let arg_path_type = ty_path(arg_path_type, cx.next_id());
+    let arg_path_type = @{
+        id: cx.next_id(),
+        node: move arg_path_type,
+        span: span
+    };
+    let arg_region = @{ id: cx.next_id(), node: re_anon };
+    let arg_type = ty_rptr(arg_region, { ty: arg_path_type, mutbl: m_imm });
+    let arg_type = @{ id: cx.next_id(), node: move arg_type, span: span };
+
+    // Create the `other` parameter.
+    let other_ident = cx.ident_of(~"__other");
+    let arg_pat = build::mk_pat_ident(cx, span, other_ident);
+    let arg = {
+        mode: infer(cx.next_id()),
+        ty: arg_type,
+        pat: arg_pat,
+        id: cx.next_id()
+    };
+
+    // Create the type of the return value.
+    let bool_ident = cx.ident_of(~"bool");
+    let output_type = build::mk_raw_path(span, ~[ bool_ident ]);
+    let output_type = ty_path(output_type, cx.next_id());
+    let output_type = @{
+        id: cx.next_id(),
+        node: move output_type,
+        span: span
+    };
+
+    // Create the function declaration.
+    let fn_decl = {
+        inputs: ~[ move arg ],
+        output: output_type,
+        cf: return_val
+    };
+
+    // Create the body block.
+    let body_block = build::mk_simple_block(cx, span, body);
+
+    // Create the method.
+    let self_ty = { node: sty_region(m_imm), span: span };
+    return @{
+        ident: method_ident,
+        attrs: ~[],
+        tps: ~[],
+        self_ty: self_ty,
+        purity: pure_fn,
+        decl: move fn_decl,
+        body: move body_block,
+        id: cx.next_id(),
+        span: span,
+        self_id: cx.next_id(),
+        vis: public
+    };
+}
+
+fn create_derived_impl(cx: ext_ctxt,
+                       span: span,
+                       type_ident: ident,
+                       eq_method: @method,
+                       ne_method: @method)
+                    -> @item {
+    // Create the reference to the `core::cmp::Eq` trait.
+    let core_ident = cx.ident_of(~"core");
+    let cmp_ident = cx.ident_of(~"cmp");
+    let eq_ident = cx.ident_of(~"Eq");
+    let core_cmp_eq_idents = ~[
+        move core_ident,
+        move cmp_ident,
+        move eq_ident
+    ];
+    let core_cmp_eq_path = {
+        span: span,
+        global: false,
+        idents: move core_cmp_eq_idents,
+        rp: None,
+        types: ~[]
+    };
+    let core_cmp_eq_path = @move core_cmp_eq_path;
+    let trait_ref = {
+        path: core_cmp_eq_path,
+        ref_id: cx.next_id(),
+        impl_id: cx.next_id(),
+    };
+    let trait_ref = @move trait_ref;
+
+    // Create the type of `self`.
+    let self_type = build::mk_raw_path(span, ~[ type_ident ]);
+    let self_type = ty_path(self_type, cx.next_id());
+    let self_type = @{ id: cx.next_id(), node: move self_type, span: span };
+
+    // Create the impl item.
+    let impl_item = item_impl(~[],
+                              Some(trait_ref),
+                              self_type,
+                              ~[ eq_method, ne_method ]);
+    return create_impl_item(cx, span, move impl_item);
+}
+
+fn expand_deriving_struct_def(cx: ext_ctxt,
+                              span: span,
+                              struct_def: &struct_def,
+                              type_ident: ident)
+                           -> @item {
+    // Create the methods.
+    let eq_ident = cx.ident_of(~"eq");
+    let ne_ident = cx.ident_of(~"ne");
+    let eq_method = expand_deriving_struct_method(cx,
+                                                  span,
+                                                  struct_def,
+                                                  eq_ident,
+                                                  type_ident,
+                                                  Conjunction);
+    let ne_method = expand_deriving_struct_method(cx,
+                                                  span,
+                                                  struct_def,
+                                                  ne_ident,
+                                                  type_ident,
+                                                  Disjunction);
+
+    // Create the implementation.
+    return create_derived_impl(cx, span, type_ident, eq_method, ne_method);    
+}
+
+fn expand_deriving_struct_method(cx: ext_ctxt,
+                                 span: span,
+                                 struct_def: &struct_def,
+                                 method_ident: ident,
+                                 type_ident: ident,
+                                 junction: Junction)
+                              -> @method {
+    let self_ident = cx.ident_of(~"self");
+    let other_ident = cx.ident_of(~"__other");
+
+    let binop = junction.to_binop();
+
+    // Create the body of the method.
+    let mut outer_expr = None;
+    for struct_def.fields.each |struct_field| {
+        match struct_field.node.kind {
+            named_field(ident, _, _) => {
+                // Create the accessor for the other field.
+                let other_field = build::mk_access(cx,
+                                                   span,
+                                                   ~[ other_ident ],
+                                                   ident);
+                let other_field_ref = build::mk_addr_of(cx,
+                                                        span,
+                                                        other_field);
+
+                // Create the accessor for this field.
+                let self_field = build::mk_access(cx,
+                                                  span,
+                                                  ~[ self_ident ],
+                                                  ident);
+
+                // Call the substructure method.
+                let self_method = build::mk_access_(cx,
+                                                    span,
+                                                    self_field,
+                                                    method_ident);
+                let self_call = build::mk_call_(cx,
+                                                span,
+                                                self_method,
+                                                ~[ other_field_ref ]);
+
+                // Connect to the outer expression if necessary.
+                outer_expr = match outer_expr {
+                    None => Some(self_call),
+                    Some(old_outer_expr) => {
+                        let chain_expr = build::mk_binary(cx,
+                                                          span,
+                                                          binop,
+                                                          old_outer_expr,
+                                                          self_call);
+                        Some(chain_expr)
+                    }
+                };
+            }
+            unnamed_field => {
+                cx.span_unimpl(span, ~"unnamed fields with `deriving_eq`");
+            }
+        }
+    }
+
+    // Create the method itself.
+    let body;
+    match outer_expr {
+        None => cx.span_unimpl(span, ~"empty structs with `deriving_eq`"),
+        Some(outer_expr) => body = outer_expr,
+    }
+
+    return create_method(cx, span, method_ident, type_ident, body);
+}
+
+fn expand_deriving_enum_def(cx: ext_ctxt,
+                            span: span,
+                            enum_definition: &enum_def,
+                            type_ident: ident)
+                         -> @item {
+    // Create the methods.
+    let eq_ident = cx.ident_of(~"eq");
+    let ne_ident = cx.ident_of(~"ne");
+    let eq_method = expand_deriving_enum_method(cx,
+                                                span,
+                                                enum_definition,
+                                                eq_ident,
+                                                type_ident,
+                                                Conjunction);
+    let ne_method = expand_deriving_enum_method(cx,
+                                                span,
+                                                enum_definition,
+                                                ne_ident,
+                                                type_ident,
+                                                Disjunction);
+
+    // Create the implementation.
+    return create_derived_impl(cx, span, type_ident, eq_method, ne_method);
+}
+
+fn expand_deriving_enum_method(cx: ext_ctxt,
+                               span: span,
+                               enum_definition: &enum_def,
+                               method_ident: ident,
+                               type_ident: ident,
+                               junction: Junction)
+                            -> @method {
+    let self_ident = cx.ident_of(~"self");
+    let other_ident = cx.ident_of(~"__other");
+
+    let _binop = junction.to_binop();
+
+    let is_eq;
+    match junction {
+        Conjunction => is_eq = true,
+        Disjunction => is_eq = false,
+    }
+
+    // Create the arms of the self match in the method body.
+    let self_arms = dvec::DVec();
+    for enum_definition.variants.each |self_variant| {
+        let other_arms = dvec::DVec();
+        let self_variant_ident = self_variant.node.name;
+
+        // Create the matching pattern.
+        let matching_pat = build::mk_pat_ident(cx, span, self_variant_ident);
+
+        // Create the matching pattern body.
+        let matching_body_expr = build::mk_bool(cx, span, is_eq);
+        let matching_body_block = build::mk_simple_block(cx,
+                                                         span,
+                                                         matching_body_expr);
+
+        // Create the matching arm.
+        let matching_arm = {
+            pats: ~[ matching_pat ],
+            guard: None,
+            body: move matching_body_block
+        };
+        other_arms.push(move matching_arm);
+
+        // Create the nonmatching pattern.
+        let nonmatching_pat = @{
+            id: cx.next_id(),
+            node: pat_wild,
+            span: span
+        };
+
+        // Create the nonmatching pattern body.
+        let nonmatching_expr = build::mk_bool(cx, span, !is_eq);
+        let nonmatching_body_block = build::mk_simple_block(cx,
+                                                            span,
+                                                            nonmatching_expr);
+
+        // Create the nonmatching arm.
+        let nonmatching_arm = {
+            pats: ~[ nonmatching_pat ],
+            guard: None,
+            body: move nonmatching_body_block
+        };
+        other_arms.push(move nonmatching_arm);
+
+        // Create the self pattern.
+        let self_pat = build::mk_pat_ident(cx, span, self_variant_ident);
+
+        // Create the self pattern body.
+        let other_expr = build::mk_path(cx, span, ~[ other_ident ]);
+        let other_expr = build::mk_unary(cx, span, deref, other_expr);
+        let other_arms = dvec::unwrap(move other_arms);
+        let other_match_expr = expr_match(other_expr, move other_arms);
+        let other_match_expr = build::mk_expr(cx,
+                                              span,
+                                              move other_match_expr);
+        let other_match_body_block = build::mk_simple_block(cx,
+                                                            span,
+                                                            other_match_expr);
+
+        // Create the self arm.
+        let self_arm = {
+            pats: ~[ self_pat ],
+            guard: None,
+            body: move other_match_body_block
+        };
+        self_arms.push(move self_arm);
+    }
+
+    // Create the method body.
+    let self_expr = build::mk_path(cx, span, ~[ self_ident ]);
+    let self_expr = build::mk_unary(cx, span, deref, self_expr);
+    let self_arms = dvec::unwrap(move self_arms);
+    let self_match_expr = expr_match(self_expr, move self_arms);
+    let self_match_expr = build::mk_expr(cx, span, move self_match_expr);
+
+    // Create the method.
+    return create_method(cx, span, method_ident, type_ident, self_match_expr);
+}
+
diff --git a/src/libsyntax/syntax.rc b/src/libsyntax/syntax.rc
index 718c916df46..2837e8fc64f 100644
--- a/src/libsyntax/syntax.rc
+++ b/src/libsyntax/syntax.rc
@@ -103,6 +103,7 @@ mod ext {
     mod qquote;
 
     mod quote;
+    mod deriving;
 
     #[legacy_exports]
     mod build;
diff --git a/src/test/run-pass/deriving-via-extension-c-enum.rs b/src/test/run-pass/deriving-via-extension-c-enum.rs
new file mode 100644
index 00000000000..54df7d84798
--- /dev/null
+++ b/src/test/run-pass/deriving-via-extension-c-enum.rs
@@ -0,0 +1,16 @@
+#[deriving_eq]
+enum Foo {
+    Bar,
+    Baz,
+    Boo
+}
+
+fn main() {
+    let a = Bar;
+    let b = Bar;
+    assert a == b;
+    assert !(a != b);
+    assert a.eq(&b);
+    assert !a.ne(&b);
+}
+
diff --git a/src/test/run-pass/deriving-via-extension-struct.rs b/src/test/run-pass/deriving-via-extension-struct.rs
new file mode 100644
index 00000000000..169fad63376
--- /dev/null
+++ b/src/test/run-pass/deriving-via-extension-struct.rs
@@ -0,0 +1,16 @@
+#[deriving_eq]
+struct Foo {
+    x: int,
+    y: int,
+    z: int,
+}
+
+fn main() {
+    let a = Foo { x: 1, y: 2, z: 3 };
+    let b = Foo { x: 1, y: 2, z: 3 };
+    assert a == b;
+    assert !(a != b);
+    assert a.eq(&b);
+    assert !a.ne(&b);
+}
+