First stab at operator overloading

When no built-in interpretation is found for one of the operators
mentioned below, the typechecker will try to turn it into a method
call with the name written next to it. For binary operators, the
method will be called on the LHS with the RHS as only parameter.

Binary:

    +   op_add
    -   op_sub
    *   op_mul
    /   op_div
    %   op_rem
    &   op_and
    |   op_or
    ^   op_xor
    <<  op_shift_left
    >>  op_shift_right
    >>> op_ashift_right

Unary:

    -   op_neg
    !   op_not

Overloading of the indexing ([]) operator isn't finished yet.

Issue #1520

2 files changed, 9 insertions, 0 deletions

diff --git a/src/comp/syntax/ast_util.rs b/src/comp/syntax/ast_util.rs
index cb0545c07b7..65c117cfa6b 100644
--- a/src/comp/syntax/ast_util.rs
+++ b/src/comp/syntax/ast_util.rs
@@ -326,6 +326,11 @@ fn ident_to_path(s: span, i: ident) -> @path {
     @respan(s, {global: false, idents: [i], types: []})
 }
 
+// Provides an extra node_id to hang callee information on, in case the
+// operator is deferred to a user-supplied method. The parser is responsible
+// for reserving this id.
+fn op_expr_callee_id(e: @expr) -> node_id { e.id - 1 }
+
 // Local Variables:
 // mode: rust
 // fill-column: 78;
diff --git a/src/comp/syntax/parse/parser.rs b/src/comp/syntax/parse/parser.rs
index a66b223175c..1e892eb43b1 100644
--- a/src/comp/syntax/parse/parser.rs
+++ b/src/comp/syntax/parse/parser.rs
@@ -1048,6 +1048,7 @@ fn parse_prefix_expr(p: parser) -> pexpr {
         p.bump();
         let e = to_expr(parse_prefix_expr(p));
         hi = e.span.hi;
+        p.get_id(); // see ast_util::op_expr_callee_id
         ex = ast::expr_unary(ast::not, e);
       }
       token::BINOP(b) {
@@ -1056,6 +1057,7 @@ fn parse_prefix_expr(p: parser) -> pexpr {
             p.bump();
             let e = to_expr(parse_prefix_expr(p));
             hi = e.span.hi;
+            p.get_id(); // see ast_util::op_expr_callee_id
             ex = ast::expr_unary(ast::neg, e);
           }
           token::STAR {
@@ -1146,6 +1148,7 @@ fn parse_more_binops(p: parser, plhs: pexpr, min_prec: int) ->
             p.bump();
             let expr = parse_prefix_expr(p);
             let rhs = parse_more_binops(p, expr, cur.prec);
+            p.get_id(); // see ast_util::op_expr_callee_id
             let bin = mk_pexpr(p, lhs.span.lo, rhs.span.hi,
                               ast::expr_binary(cur.op, lhs, rhs));
             ret parse_more_binops(p, bin, min_prec);
@@ -1186,6 +1189,7 @@ fn parse_assign_expr(p: parser) -> @ast::expr {
           token::LSR { aop = ast::lsr; }
           token::ASR { aop = ast::asr; }
         }
+        p.get_id(); // see ast_util::op_expr_callee_id
         ret mk_expr(p, lo, rhs.span.hi, ast::expr_assign_op(aop, lhs, rhs));
       }
       token::LARROW {