From 42f95d055c2f22078f5c94c0d0ca229e1561ccb8 Mon Sep 17 00:00:00 2001
From: Luqman Aden <me@luqman.ca>
Date: Mon, 4 Mar 2013 18:03:21 -0800
Subject: [PATCH] Allow constant expressions in [Type * n].

---
 src/librustc/middle/typeck/astconv.rs | 27 ++++++++++++++++++++++++---
 src/libsyntax/ast.rs                  |  2 +-
 src/libsyntax/parse/parser.rs         | 21 ++++-----------------
 src/libsyntax/print/pprust.rs         |  6 +++---
 4 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/src/librustc/middle/typeck/astconv.rs b/src/librustc/middle/typeck/astconv.rs
index 8e0633c10cd..2a70ba7d4c1 100644
--- a/src/librustc/middle/typeck/astconv.rs
+++ b/src/librustc/middle/typeck/astconv.rs
@@ -54,6 +54,7 @@
 
 use core::prelude::*;
 
+use middle::const_eval;
 use middle::ty::{arg, field, substs};
 use middle::ty::{ty_param_substs_and_ty};
 use middle::ty;
@@ -412,9 +413,29 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:region_scope + Copy + Durable>(
           }
         }
       }
-      ast::ty_fixed_length_vec(a_mt, u) => {
-        ty::mk_evec(tcx, ast_mt_to_mt(self, rscope, a_mt),
-                    ty::vstore_fixed(u))
+      ast::ty_fixed_length_vec(a_mt, e) => {
+        match const_eval::eval_const_expr_partial(tcx, e) {
+          Ok(ref r) => {
+            match *r {
+              const_eval::const_int(i) =>
+                ty::mk_evec(tcx, ast_mt_to_mt(self, rscope, a_mt),
+                            ty::vstore_fixed(i as uint)),
+              const_eval::const_uint(i) =>
+                ty::mk_evec(tcx, ast_mt_to_mt(self, rscope, a_mt),
+                            ty::vstore_fixed(i as uint)),
+              _ => {
+                tcx.sess.span_fatal(
+                    ast_ty.span, ~"expected constant expr for vector length");
+              }
+            }
+          }
+          Err(ref r) => {
+            tcx.sess.span_fatal(
+                ast_ty.span,
+                fmt!("expected constant expr for vector length: %s",
+                     *r));
+          }
+        }
       }
       ast::ty_infer => {
         // ty_infer should only appear as the type of arguments or return
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index e5fb2ad153c..e2e750e8903 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -916,7 +916,7 @@ pub enum ty_ {
     ty_box(mt),
     ty_uniq(mt),
     ty_vec(mt),
-    ty_fixed_length_vec(mt, uint),
+    ty_fixed_length_vec(mt, @expr),
     ty_ptr(mt),
     ty_rptr(Option<@Lifetime>, mt),
     ty_closure(@TyClosure),
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 8a883b73a64..c7e93635d4c 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -642,7 +642,8 @@ pub impl Parser {
                 self.obsolete(*self.last_span, ObsoleteMutVector);
             }
 
-            // Parse the `* 3` in `[ int * 3 ]`
+            // Parse the `* e` in `[ int * e ]`
+            // where `e` is a const expression
             let t = match self.maybe_parse_fixed_vstore_with_star() {
                 None => ty_vec(mt),
                 Some(suffix) => ty_fixed_length_vec(mt, suffix)
@@ -814,23 +815,9 @@ pub impl Parser {
         })
     }
 
-    fn maybe_parse_fixed_vstore_with_star(&self) -> Option<uint> {
+    fn maybe_parse_fixed_vstore_with_star(&self) -> Option<@ast::expr> {
         if self.eat(&token::BINOP(token::STAR)) {
-            match *self.token {
-                token::LIT_INT_UNSUFFIXED(i) if i >= 0i64 => {
-                    self.bump();
-                    Some(i as uint)
-                }
-                _ => {
-                    self.fatal(
-                        fmt!(
-                            "expected integral vector length \
-                            but found `%s`",
-                            token_to_str(self.reader, &copy *self.token)
-                        )
-                    );
-                }
-            }
+            Some(self.parse_expr())
         } else {
             None
         }
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 71f3de17414..ab7fe8dc063 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -425,7 +425,7 @@ pub fn print_type_ex(s: @ps, &&ty: @ast::Ty, print_colons: bool) {
         }
         print_type(s, mt.ty);
         word(s.s, ~" * ");
-        word(s.s, fmt!("%u", v));
+        word(s.s, fmt!("%?", v));
         word(s.s, ~"]");
       }
       ast::ty_mac(_) => {
@@ -1015,7 +1015,7 @@ pub fn print_mac(s: @ps, m: ast::mac) {
 
 pub fn print_vstore(s: @ps, t: ast::vstore) {
     match t {
-        ast::vstore_fixed(Some(i)) => word(s.s, fmt!("%u", i)),
+        ast::vstore_fixed(Some(i)) => word(s.s, fmt!("%?", i)),
         ast::vstore_fixed(None) => word(s.s, ~"_"),
         ast::vstore_uniq => word(s.s, ~"~"),
         ast::vstore_box => word(s.s, ~"@"),
@@ -1028,7 +1028,7 @@ pub fn print_vstore(s: @ps, t: ast::vstore) {
 
 pub fn print_expr_vstore(s: @ps, t: ast::expr_vstore) {
     match t {
-      ast::expr_vstore_fixed(Some(i)) => word(s.s, fmt!("%u", i)),
+      ast::expr_vstore_fixed(Some(i)) => word(s.s, fmt!("%?", i)),
       ast::expr_vstore_fixed(None) => word(s.s, ~"_"),
       ast::expr_vstore_uniq => word(s.s, ~"~"),
       ast::expr_vstore_box => word(s.s, ~"@"),