From 8a7a0308e32711dce241142dac6c97ccd3a74807 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Mon, 11 Oct 2010 18:13:14 -0700
Subject: [PATCH] rustc: Parse lets

---
 src/comp/front/ast.rs    |  2 +-
 src/comp/front/parser.rs | 27 +++++++++++++++++++++++++++
 src/comp/middle/fold.rs  | 10 +++++-----
 3 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index 0b0f571ce2a..34df06add68 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -76,7 +76,7 @@ tag stmt_ {
 
 type decl = spanned[decl_];
 tag decl_ {
-    decl_local(ident, bool, option[@ty]);
+    decl_local(ident, option[@ty], option[@expr]);
     decl_item(name, @item);
 }
 
diff --git a/src/comp/front/parser.rs b/src/comp/front/parser.rs
index 2571c5d7918..877119de914 100644
--- a/src/comp/front/parser.rs
+++ b/src/comp/front/parser.rs
@@ -541,6 +541,27 @@ io fn parse_expr(parser p) -> @ast.expr {
     }
 }
 
+io fn parse_let(parser p) -> @ast.decl {
+    auto lo = p.get_span();
+
+    expect(p, token.LET);
+    auto ty = parse_ty(p);
+    auto id = parse_ident(p);
+
+    auto init;
+    if (p.peek() == token.EQ) {
+        p.bump();
+        init = some(parse_expr(p));
+    } else {
+        init = none[@ast.expr];
+    }
+
+    expect(p, token.SEMI);
+
+    auto hi = p.get_span();
+    ret @spanned(lo, hi, ast.decl_local(id, some(ty), init));
+}
+
 io fn parse_stmt(parser p) -> @ast.stmt {
     auto lo = p.get_span();
     alt (p.peek()) {
@@ -553,6 +574,12 @@ io fn parse_stmt(parser p) -> @ast.stmt {
             ret @spanned(lo, hi, ast.stmt_log(e));
         }
 
+        case (token.LET) {
+            auto leht = parse_let(p);
+            auto hi = p.get_span();
+            ret @spanned(lo, hi, ast.stmt_decl(leht));
+        }
+
         // Handle the (few) block-expr stmts first.
 
         case (token.IF) {
diff --git a/src/comp/middle/fold.rs b/src/comp/middle/fold.rs
index a74ac3b3985..543a05e1ede 100644
--- a/src/comp/middle/fold.rs
+++ b/src/comp/middle/fold.rs
@@ -85,8 +85,8 @@ type ast_fold[ENV] =
 
      // Decl folds.
      (fn(&ENV e, &span sp,
-         ident ident, bool infer,
-         &option[@ty] ty) -> @decl)               fold_decl_local,
+         ident ident, &option[@ty] ty,
+         &option[@expr]) -> @decl)                fold_decl_local,
 
      (fn(&ENV e, &span sp,
          &name name, @item item) -> @decl)        fold_decl_item,
@@ -483,9 +483,9 @@ fn identity_fold_expr_block[ENV](&ENV env, &span sp, block blk) -> @expr {
 // Decl identities.
 
 fn identity_fold_decl_local[ENV](&ENV e, &span sp,
-                                 ident i, bool infer,
-                                 &option[@ty] t) -> @decl {
-    ret @respan(sp, ast.decl_local(i, infer, t));
+                                 ident i, &option[@ty] t,
+                                 &option[@expr] init) -> @decl {
+    ret @respan(sp, ast.decl_local(i, t, init));
 }
 
 fn identity_fold_decl_item[ENV](&ENV e, &span sp,