Disallow rebinding / matching against consts in alts

As per Issue #1193. Closes #1193.

I had to rename a few variables ("info" and "epsilon") to avoid
clashing with in-scope constants, which is responsible for all the
changes other than resolve and issue-1193.rs.

src/libcore/float.rs

@@ -51,10 +51,10 @@ fn to_str_common(num: float, digits: uint, exact: bool) -> str {
     if (frac < epsilon && !exact) || digits == 0u { ret accum; }
     accum += ".";
     let mut i = digits;
-    let mut epsilon = 1. / pow_with_uint(10u, i);
+    let mut epsilon_prime = 1. / pow_with_uint(10u, i);
-    while i > 0u && (frac >= epsilon || exact) {
+    while i > 0u && (frac >= epsilon_prime || exact) {
         frac *= 10.0;
-        epsilon *= 10.0;
+        epsilon_prime *= 10.0;
         let digit = frac as uint;
         accum += uint::str(digit);
         frac -= digit as float;

src/librustsyntax/ext/expand.rs

@@ -34,9 +34,8 @@ fn expand_expr(exts: hashmap<str, syntax_extension>, cx: ext_ctxt,
                   some(normal({expander: exp, span: exp_sp})) {
                     let expanded = exp(cx, pth.span, args, body);
 
-                    let info = {call_site: s,
+                    cx.bt_push(expanded_from({call_site: s,
-                                callie: {name: extname, span: exp_sp}};
+                                callie: {name: extname, span: exp_sp}}));
-                    cx.bt_push(expanded_from(info));
                     //keep going, outside-in
                     let fully_expanded = fld.fold_expr(expanded).node;
                     cx.bt_pop();

src/rustc/middle/resolve.rs

@@ -500,19 +500,23 @@ fn resolve_names(e: @env, c: @ast::crate) {
               }
               _ {
                 e.sess.span_err(p.span,
-                                "not a enum variant: " +
+                                "not an enum variant: " +
                                     ast_util::path_name(p));
               }
             }
           }
           /* Here we determine whether a given pat_ident binds a new
-           variable a refers to a nullary enum. */
+           variable or refers to a nullary enum. */
           ast::pat_ident(p, none) {
               alt lookup_in_scope(*e, sc, p.span, path_to_ident(p),
                                   ns_val, false) {
                 some(fnd@ast::def_variant(_,_)) {
                     e.def_map.insert(pat.id, fnd);
                 }
+                some(fnd@ast::def_const(_)) {
+                    e.sess.span_err(p.span, "Sorry, rebinding or matching \
+                      against symbolic constants is not allowed.");
+                }
                 // Binds a var -- nothing needs to be done
                 _ {}
               }
@@ -1446,16 +1450,16 @@ fn list_search<T: copy, U: copy>(ls: list<T>, f: fn(T) -> option<U>)
 
 fn lookup_in_local_mod(e: env, node_id: node_id, sp: span, id: ident,
                        ns: namespace, dr: dir) -> option<def> {
-    let info = alt e.mod_map.find(node_id) {
+    let inf = alt e.mod_map.find(node_id) {
             some(x) { x }
             none { e.sess.span_bug(sp, #fmt("lookup_in_local_mod: \
                      module %d not in mod_map", node_id)); }
     };
-    if dr == outside && !is_exported(e, id, info) {
+    if dr == outside && !is_exported(e, id, inf) {
-        // if we're in a native mod, then dr==inside, so info.m is some _mod
+        // if we're in a native mod, then dr==inside, so inf.m is some _mod
         ret none; // name is not visible
     }
-    alt info.index.find(id) {
+    alt inf.index.find(id) {
       none { }
       some(lst) {
         let found = list_search(lst, bind lookup_in_mie(e, _, ns));
@@ -1465,7 +1469,7 @@ fn lookup_in_local_mod(e: env, node_id: node_id, sp: span, id: ident,
       }
     }
     // not local or explicitly imported; try globs:
-    ret lookup_glob_in_mod(e, info, sp, id, ns, outside);
+    ret lookup_glob_in_mod(e, inf, sp, id, ns, outside);
 }
 
 fn lookup_in_globs(e: env, globs: [glob_imp_def], sp: span, id: ident,

src/rustc/middle/trans/base.rs

@@ -371,19 +371,19 @@ fn get_tydesc(ccx: @crate_ctxt, t: ty::t,
               &static_ti: option<@tydesc_info>) -> ValueRef {
     assert !ty::type_has_params(t);
     // Otherwise, generate a tydesc if necessary, and return it.
-    let info = get_static_tydesc(ccx, t);
+    let inf = get_static_tydesc(ccx, t);
-    static_ti = some(info);
+    static_ti = some(inf);
-    info.tydesc
+    inf.tydesc
 }
 
 fn get_static_tydesc(ccx: @crate_ctxt, t: ty::t) -> @tydesc_info {
     alt ccx.tydescs.find(t) {
-      some(info) { ret info; }
+      some(inf) { ret inf; }
       none {
         ccx.stats.n_static_tydescs += 1u;
-        let info = declare_tydesc(ccx, t);
+        let inf = declare_tydesc(ccx, t);
-        ccx.tydescs.insert(t, info);
+        ccx.tydescs.insert(t, inf);
-        ret info;
+        ret inf;
       }
     }
 }
@@ -455,7 +455,7 @@ fn declare_tydesc(ccx: @crate_ctxt, t: ty::t) -> @tydesc_info {
     let gvar = str::as_c_str(name, {|buf|
         llvm::LLVMAddGlobal(ccx.llmod, ccx.tydesc_type, buf)
     });
-    let info =
+    let inf =
         @{ty: t,
           tydesc: gvar,
           size: llsize,
@@ -464,7 +464,7 @@ fn declare_tydesc(ccx: @crate_ctxt, t: ty::t) -> @tydesc_info {
           mut drop_glue: none,
           mut free_glue: none};
     log(debug, "--- declare_tydesc " + ty_to_str(ccx.tcx, t));
-    ret info;
+    ret inf;
 }
 
 type glue_helper = fn@(block, ValueRef, ty::t);
@@ -2870,8 +2870,8 @@ fn need_invoke(bcx: block) -> bool {
     let mut cur = bcx;
     loop {
         alt cur.kind {
-          block_scope(info) {
+          block_scope(inf) {
-            for info.cleanups.each {|cleanup|
+            for inf.cleanups.each {|cleanup|
                 alt cleanup {
                   clean(_, cleanup_type) | clean_temp(_, _, cleanup_type) {
                     if cleanup_type == normal_exit_and_unwind {
@@ -2892,8 +2892,8 @@ fn need_invoke(bcx: block) -> bool {
 
 fn have_cached_lpad(bcx: block) -> bool {
     let mut res = false;
-    in_lpad_scope_cx(bcx) {|info|
+    in_lpad_scope_cx(bcx) {|inf|
-        alt info.landing_pad {
+        alt inf.landing_pad {
           some(_) { res = true; }
           none { res = false; }
         }
@@ -2905,9 +2905,9 @@ fn in_lpad_scope_cx(bcx: block, f: fn(scope_info)) {
     let mut bcx = bcx;
     loop {
         alt bcx.kind {
-          block_scope(info) {
+          block_scope(inf) {
-            if info.cleanups.len() > 0u || bcx.parent == parent_none {
+            if inf.cleanups.len() > 0u || bcx.parent == parent_none {
-                f(info); ret;
+                f(inf); ret;
             }
           }
           _ {}
@@ -2920,13 +2920,13 @@ fn get_landing_pad(bcx: block) -> BasicBlockRef {
     let _icx = bcx.insn_ctxt("get_landing_pad");
 
     let mut cached = none, pad_bcx = bcx; // Guaranteed to be set below
-    in_lpad_scope_cx(bcx) {|info|
+    in_lpad_scope_cx(bcx) {|inf|
         // If there is a valid landing pad still around, use it
-        alt info.landing_pad {
+        alt inf.landing_pad {
           some(target) { cached = some(target); }
           none {
             pad_bcx = sub_block(bcx, "unwind");
-            info.landing_pad = some(pad_bcx.llbb);
+            inf.landing_pad = some(pad_bcx.llbb);
           }
         }
     }
@@ -3792,8 +3792,8 @@ fn cleanup_and_leave(bcx: block, upto: option<BasicBlockRef>,
     let mut done = false;
     loop {
         alt cur.kind {
-          block_scope(info) if info.cleanups.len() > 0u {
+          block_scope(inf) if inf.cleanups.len() > 0u {
-            option::iter(vec::find(info.cleanup_paths,
+            option::iter(vec::find(inf.cleanup_paths,
                                              {|cp| cp.target == leave})) {|cp|
                 Br(bcx, cp.dest);
                 done = true;
@@ -3801,7 +3801,7 @@ fn cleanup_and_leave(bcx: block, upto: option<BasicBlockRef>,
             if done { ret; }
             let sub_cx = sub_block(bcx, "cleanup");
             Br(bcx, sub_cx.llbb);
-            info.cleanup_paths += [{target: leave, dest: sub_cx.llbb}];
+            inf.cleanup_paths += [{target: leave, dest: sub_cx.llbb}];
             bcx = trans_block_cleanups_(sub_cx, cur, is_lpad);
           }
           _ {}

src/rustc/middle/trans/common.rs

@@ -381,7 +381,7 @@ fn in_scope_cx(cx: block, f: fn(scope_info)) {
     let mut cur = cx;
     loop {
         alt cur.kind {
-          block_scope(info) { f(info); ret; }
+          block_scope(inf) { f(inf); ret; }
           _ {}
         }
         cur = block_parent(cur);

src/rustc/middle/trans/shape.rs

@@ -514,16 +514,16 @@ fn gen_enum_shapes(ccx: @crate_ctxt) -> ValueRef {
     // to each variant shape). As we do so, build up the header.
 
     let mut header = [];
-    let mut info = [];
+    let mut inf = [];
     let header_sz = 2u16 * ccx.shape_cx.next_tag_id;
     let data_sz = vec::len(data) as u16;
 
-    let mut info_sz = 0u16;
+    let mut inf_sz = 0u16;
     for ccx.shape_cx.tag_order.each {|did_|
         let did = did_; // Satisfy alias checker.
         let num_variants = vec::len(*ty::enum_variants(ccx.tcx, did)) as u16;
-        add_u16(header, header_sz + info_sz);
+        add_u16(header, header_sz + inf_sz);
-        info_sz += 2u16 * (num_variants + 2u16) + 3u16;
+        inf_sz += 2u16 * (num_variants + 2u16) + 3u16;
     }
 
     // Construct the info tables, which contain offsets to the shape of each
@@ -535,11 +535,11 @@ fn gen_enum_shapes(ccx: @crate_ctxt) -> ValueRef {
     for ccx.shape_cx.tag_order.each {|did_|
         let did = did_; // Satisfy alias checker.
         let variants = ty::enum_variants(ccx.tcx, did);
-        add_u16(info, vec::len(*variants) as u16);
+        add_u16(inf, vec::len(*variants) as u16);
 
         // Construct the largest-variants table.
-        add_u16(info,
+        add_u16(inf,
-                header_sz + info_sz + data_sz + (vec::len(lv_table) as u16));
+                header_sz + inf_sz + data_sz + (vec::len(lv_table) as u16));
 
         let lv = largest_variants(ccx, did);
         add_u16(lv_table, vec::len(lv) as u16);
@@ -555,22 +555,22 @@ fn gen_enum_shapes(ccx: @crate_ctxt) -> ValueRef {
         let size_align = if dynamic { {size: 0u16, align: 0u8} }
                          else { compute_static_enum_size(ccx, lv, did) };
         // Write in the static size and alignment of the enum.
-        add_u16(info, size_align.size);
+        add_u16(inf, size_align.size);
-        info += [size_align.align];
+        inf += [size_align.align];
 
         // Now write in the offset of each variant.
         for vec::each(*variants) {|_v|
-            add_u16(info, header_sz + info_sz + offsets[i]);
+            add_u16(inf, header_sz + inf_sz + offsets[i]);
             i += 1u;
         }
     }
 
     assert (i == vec::len(offsets));
     assert (header_sz == vec::len(header) as u16);
-    assert (info_sz == vec::len(info) as u16);
+    assert (inf_sz == vec::len(inf) as u16);
     assert (data_sz == vec::len(data) as u16);
 
-    header += info;
+    header += inf;
     header += data;
     header += lv_table;
 

src/test/compile-fail/issue-1193.rs

@@ -0,0 +1,14 @@
+// error-pattern: Sorry, rebinding or matching against symbolic
+mod foo {
+    type t = u8;
+
+    const a : t = 0u8;
+    const b : t = 1u8;
+
+    fn bar(v: t) -> bool {
+        alt v {
+            a { ret true; }
+            b { ret false; }
+        }
+    }
+}