From 699ef987d78db9d74a2f4e3e5849355998d7b407 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Wed, 13 Oct 2010 12:43:35 -0700
Subject: rustc: Start work on lvals

---
 src/comp/front/ast.rs    | 12 ++++++++---
 src/comp/front/parser.rs | 52 ++++++++++++++++++++++++++++++++++--------------
 2 files changed, 46 insertions(+), 18 deletions(-)

(limited to 'src/comp/front')

diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index aa4ed1e7..5af9fa8b 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -89,12 +89,18 @@ tag expr_ {
     expr_binary(binop, @expr, @expr);
     expr_unary(unop, @expr);
     expr_lit(@lit);
-    expr_name(name, option[referent]);
-    expr_field(@expr, ident);
-    expr_index(@expr, @expr);
     expr_cast(@expr, @ty);
     expr_if(@expr, block, option[block]);
     expr_block(block);
+    expr_assign(@lval, @expr);
+    expr_lval(@lval);
+}
+
+type lval = spanned[lval_];
+tag lval_ {
+    lval_field(@expr, ident);
+    lval_index(@expr, @expr);
+    lval_name(name, option[referent]);
 }
 
 type lit = spanned[lit_];
diff --git a/src/comp/front/parser.rs b/src/comp/front/parser.rs
index d731bf70..d6968a5b 100644
--- a/src/comp/front/parser.rs
+++ b/src/comp/front/parser.rs
@@ -238,6 +238,25 @@ io fn parse_possibly_mutable_expr(parser p) -> tup(bool, @ast.expr) {
     ret tup(mut, parse_expr(p));
 }
 
+io fn parse_lval(parser p) -> option[@ast.lval] {
+    auto lo = p.get_span();
+
+    alt (p.peek()) {
+        case (token.IDENT(?i)) {
+            auto n = parse_name(p, i);
+            auto hi = n.span;
+            auto lval = ast.lval_name(n, none[ast.referent]);
+            ret some(@spanned(lo, hi, lval));
+        }
+
+        case (_) {
+            ret none[@ast.lval];
+        }
+    }
+
+    fail;
+}
+
 io fn parse_bottom_expr(parser p) -> @ast.expr {
 
     auto lo = p.get_span();
@@ -297,21 +316,22 @@ io fn parse_bottom_expr(parser p) -> @ast.expr {
             ex = ast.expr_rec(es.node);
         }
 
-        case (token.IDENT(?i)) {
-            auto n = parse_name(p, i);
-            hi = n.span;
-            ex = ast.expr_name(n, none[ast.referent]);
-        }
-
         case (_) {
-            alt (parse_lit(p)) {
-                case (some[ast.lit](?lit)) {
-                    hi = lit.span;
-                    ex = ast.expr_lit(@lit);
+            alt (parse_lval(p)) {
+                case (some[@ast.lval](?lval)) {
+                    hi = lval.span;
+                    ex = ast.expr_lval(lval);
                 }
-                case (none[ast.lit]) {
-                    p.err("expecting expression");
-                    fail;
+                case (none[@ast.lval]) {
+                    alt (parse_lit(p)) {
+                        case (some[ast.lit](?lit)) {
+                            hi = lit.span;
+                            ex = ast.expr_lit(@lit);
+                        }
+                        case (none[ast.lit]) {
+                            p.err("expecting expression");
+                        }
+                    }
                 }
             }
         }
@@ -332,13 +352,15 @@ io fn parse_path_expr(parser p) -> @ast.expr {
                     case (token.IDENT(?i)) {
                         hi = p.get_span();
                         p.bump();
-                        e = @spanned(lo, hi, ast.expr_field(e, i));
+                        auto lv = @spanned(lo, hi, ast.lval_field(e, i));
+                        e = @spanned(lo, hi, ast.expr_lval(lv));
                     }
 
                     case (token.LPAREN) {
                         auto ix = parse_bottom_expr(p);
                         hi = ix.span;
-                        e = @spanned(lo, hi, ast.expr_index(e, ix));
+                        auto lv = @spanned(lo, hi, ast.lval_index(e, ix));
+                        e = @spanned(lo, hi, ast.expr_lval(lv));
                     }
                 }
             }
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