diff --git a/src/libfuzzer/fuzzer.rc b/src/libfuzzer/fuzzer.rc
index 8257af5760f..19afbc4b2b7 100644
--- a/src/libfuzzer/fuzzer.rc
+++ b/src/libfuzzer/fuzzer.rc
@@ -109,8 +109,7 @@ pub pure fn safe_to_use_expr(e: ast::expr, tm: test_mode) -> bool {
           | ast::expr_match(*) | ast::expr_while(*)  => { false }
 
           // https://github.com/mozilla/rust/issues/929
-          ast::expr_cast(*) | ast::expr_assert(*) |
-          ast::expr_binary(*) | ast::expr_assign(*) |
+          ast::expr_cast(*) | ast::expr_binary(*) | ast::expr_assign(*) |
           ast::expr_assign_op(*) => { false }
 
           ast::expr_ret(option::None) => { false }
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 473fad5ee25..5d652571ab1 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -617,11 +617,11 @@ fn visit_expr(expr: @expr, &&self: @mut IrMaps, vt: vt<@mut IrMaps>) {
       // otherwise, live nodes are not required:
       expr_index(*) | expr_field(*) | expr_vstore(*) | expr_vec(*) |
       expr_call(*) | expr_method_call(*) | expr_tup(*) | expr_log(*) |
-      expr_binary(*) | expr_assert(*) | expr_addr_of(*) | expr_copy(*) |
-      expr_loop_body(*) | expr_do_body(*) | expr_cast(*) | expr_unary(*) |
-      expr_break(_) | expr_again(_) | expr_lit(_) | expr_ret(*) |
-      expr_block(*) | expr_assign(*) | expr_swap(*) | expr_assign_op(*) |
-      expr_mac(*) | expr_struct(*) | expr_repeat(*) | expr_paren(*) => {
+      expr_binary(*) | expr_addr_of(*) | expr_copy(*) | expr_loop_body(*) |
+      expr_do_body(*) | expr_cast(*) | expr_unary(*) | expr_break(_) |
+      expr_again(_) | expr_lit(_) | expr_ret(*) | expr_block(*) |
+      expr_assign(*) | expr_swap(*) | expr_assign_op(*) | expr_mac(*) |
+      expr_struct(*) | expr_repeat(*) | expr_paren(*) => {
           visit::visit_expr(expr, self, vt);
       }
     }
@@ -1332,7 +1332,6 @@ fn propagate_through_expr(&self, expr: @expr, succ: LiveNode)
             self.propagate_through_exprs(~[l, r], succ)
           }
 
-          expr_assert(e) |
           expr_addr_of(_, e) |
           expr_copy(e) |
           expr_loop_body(e) |
@@ -1493,8 +1492,9 @@ fn propagate_through_loop(&self, expr: @expr,
         // repeat until fixed point is reached:
         while self.merge_from_succ(ln, body_ln, first_merge) {
             first_merge = false;
-            fail_unless!(cond_ln == self.propagate_through_opt_expr(cond, ln));
-            assert body_ln == self.with_loop_nodes(expr.id, succ, ln,
+            fail_unless!(cond_ln == self.propagate_through_opt_expr(cond,
+                                                                    ln));
+            fail_unless!(body_ln == self.with_loop_nodes(expr.id, succ, ln,
             || {
                 self.propagate_through_block(body, cond_ln)
             }));
@@ -1611,11 +1611,11 @@ fn check_expr(expr: @expr, &&self: @Liveness, vt: vt<@Liveness>) {
       expr_call(*) | expr_method_call(*) | expr_if(*) | expr_match(*) |
       expr_while(*) | expr_loop(*) | expr_index(*) | expr_field(*) |
       expr_vstore(*) | expr_vec(*) | expr_tup(*) | expr_log(*) |
-      expr_binary(*) | expr_assert(*) | expr_copy(*) | expr_loop_body(*) |
-      expr_do_body(*) | expr_cast(*) | expr_unary(*) | expr_ret(*) |
-      expr_break(*) | expr_again(*) | expr_lit(_) | expr_block(*) |
-      expr_swap(*) | expr_mac(*) | expr_addr_of(*) | expr_struct(*) |
-      expr_repeat(*) | expr_paren(*) => {
+      expr_binary(*) | expr_copy(*) | expr_loop_body(*) | expr_do_body(*) |
+      expr_cast(*) | expr_unary(*) | expr_ret(*) | expr_break(*) |
+      expr_again(*) | expr_lit(_) | expr_block(*) | expr_swap(*) |
+      expr_mac(*) | expr_addr_of(*) | expr_struct(*) | expr_repeat(*) |
+      expr_paren(*) => {
         visit::visit_expr(expr, self, vt);
       }
     }
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 18cf02cf66d..00cab7961ca 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -437,19 +437,17 @@ fn cat_expr_unadjusted(&self, expr: @ast::expr) -> cmt {
 
           ast::expr_paren(e) => self.cat_expr_unadjusted(e),
 
-          ast::expr_addr_of(*) | ast::expr_call(*) |
-          ast::expr_swap(*) | ast::expr_assign(*) |
-          ast::expr_assign_op(*) | ast::expr_fn_block(*) |
-          ast::expr_assert(*) | ast::expr_ret(*) |
-          ast::expr_loop_body(*) | ast::expr_do_body(*) |
-          ast::expr_unary(*) | ast::expr_method_call(*) |
-          ast::expr_copy(*) | ast::expr_cast(*) |
+          ast::expr_addr_of(*) | ast::expr_call(*) | ast::expr_swap(*) |
+          ast::expr_assign(*) | ast::expr_assign_op(*) |
+          ast::expr_fn_block(*) | ast::expr_ret(*) | ast::expr_loop_body(*) |
+          ast::expr_do_body(*) | ast::expr_unary(*) |
+          ast::expr_method_call(*) | ast::expr_copy(*) | ast::expr_cast(*) |
           ast::expr_vstore(*) | ast::expr_vec(*) | ast::expr_tup(*) |
-          ast::expr_if(*) | ast::expr_log(*) |
-          ast::expr_binary(*) | ast::expr_while(*) |
-          ast::expr_block(*) | ast::expr_loop(*) | ast::expr_match(*) |
-          ast::expr_lit(*) | ast::expr_break(*) | ast::expr_mac(*) |
-          ast::expr_again(*) | ast::expr_struct(*) | ast::expr_repeat(*) => {
+          ast::expr_if(*) | ast::expr_log(*) | ast::expr_binary(*) |
+          ast::expr_while(*) | ast::expr_block(*) | ast::expr_loop(*) |
+          ast::expr_match(*) | ast::expr_lit(*) | ast::expr_break(*) |
+          ast::expr_mac(*) | ast::expr_again(*) | ast::expr_struct(*) |
+          ast::expr_repeat(*) => {
             return self.cat_rvalue(expr, expr_ty);
           }
         }
diff --git a/src/librustc/middle/moves.rs b/src/librustc/middle/moves.rs
index 826fc54f054..182697b290f 100644
--- a/src/librustc/middle/moves.rs
+++ b/src/librustc/middle/moves.rs
@@ -571,10 +571,6 @@ fn use_expr(&self,
                 self.use_expr(b_expr, Read, visitor);
             }
 
-            expr_assert(cond_expr) => {
-                self.consume_expr(cond_expr, visitor);
-            }
-
             expr_while(cond_expr, ref blk) => {
                 self.consume_expr(cond_expr, visitor);
                 self.consume_block(blk, visitor);
diff --git a/src/librustc/middle/trans/controlflow.rs b/src/librustc/middle/trans/controlflow.rs
index 59c143ebce7..e60223c9eff 100644
--- a/src/librustc/middle/trans/controlflow.rs
+++ b/src/librustc/middle/trans/controlflow.rs
@@ -322,25 +322,6 @@ pub fn trans_ret(bcx: block, e: Option<@ast::expr>) -> block {
     return bcx;
 }
 
-pub fn trans_check_expr(bcx: block,
-                        chk_expr: @ast::expr,
-                        pred_expr: @ast::expr,
-                        s: &str)
-                     -> block {
-    let _icx = bcx.insn_ctxt("trans_check_expr");
-    let expr_str = @(fmt!("%s %s failed",
-                          s, expr_to_str(pred_expr, bcx.ccx().sess.intr())));
-    let Result {bcx, val} = {
-        do with_scope_result(bcx, chk_expr.info(), ~"check") |bcx| {
-            expr::trans_to_datum(bcx, pred_expr).to_result()
-        }
-    };
-    let val = bool_to_i1(bcx, val);
-    do with_cond(bcx, Not(bcx, val)) |bcx| {
-        trans_fail(bcx, Some(pred_expr.span), expr_str)
-    }
-}
-
 pub fn trans_fail_expr(bcx: block,
                        sp_opt: Option<span>,
                        fail_expr: Option<@ast::expr>)
diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index 7f9ff2a244b..b7942fa66db 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -510,9 +510,6 @@ fn trans_rvalue_stmt_unadjusted(bcx: block, expr: @ast::expr) -> block {
         ast::expr_log(_, lvl, a) => {
             return controlflow::trans_log(expr, lvl, bcx, a);
         }
-        ast::expr_assert(a) => {
-            return controlflow::trans_check_expr(bcx, expr, a, ~"Assertion");
-        }
         ast::expr_while(cond, ref body) => {
             return controlflow::trans_while(bcx, cond, body);
         }
diff --git a/src/librustc/middle/trans/type_use.rs b/src/librustc/middle/trans/type_use.rs
index 8699b4f0139..710bb5eb346 100644
--- a/src/librustc/middle/trans/type_use.rs
+++ b/src/librustc/middle/trans/type_use.rs
@@ -349,11 +349,10 @@ pub fn mark_for_expr(cx: Context, e: @expr) {
         mark_for_method_call(cx, e.id, e.callee_id);
       }
       expr_paren(e) => mark_for_expr(cx, e),
-      expr_match(*) | expr_block(_) | expr_if(*) |
-      expr_while(*) | expr_break(_) | expr_again(_) |
-      expr_unary(_, _) | expr_lit(_) | expr_assert(_) |
-      expr_mac(_) | expr_addr_of(_, _) |
-      expr_ret(_) | expr_loop(_, _) |
+
+      expr_match(*) | expr_block(_) | expr_if(*) | expr_while(*) |
+      expr_break(_) | expr_again(_) | expr_unary(_, _) | expr_lit(_) |
+      expr_mac(_) | expr_addr_of(_, _) | expr_ret(_) | expr_loop(_, _) |
       expr_loop_body(_) | expr_do_body(_) => ()
     }
 }
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 350c1526ce0..082c64ced8e 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -3114,7 +3114,6 @@ pub fn expr_kind(tcx: ctxt,
         ast::expr_again(*) |
         ast::expr_ret(*) |
         ast::expr_log(*) |
-        ast::expr_assert(*) |
         ast::expr_while(*) |
         ast::expr_loop(*) |
         ast::expr_assign(*) |
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index 65646cfcbb1..6efa62c55cc 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -2309,10 +2309,6 @@ fn check_loop_body(fcx: @mut FnCtxt,
         check_expr(fcx, e);
         fcx.write_nil(id);
       }
-      ast::expr_assert(e) => {
-        bot = check_expr_has_type(fcx, e, ty::mk_bool(tcx));
-        fcx.write_nil(id);
-      }
       ast::expr_copy(a) => {
         bot = check_expr_with_opt_hint(fcx, a, expected);
         fcx.write_ty(id, fcx.expr_ty(a));
diff --git a/src/librustc/middle/typeck/check/regionck.rs b/src/librustc/middle/typeck/check/regionck.rs
index 392182bee3f..818a444a4f3 100644
--- a/src/librustc/middle/typeck/check/regionck.rs
+++ b/src/librustc/middle/typeck/check/regionck.rs
@@ -692,7 +692,6 @@ fn guarantor(rcx: @mut Rcx, expr: @ast::expr) -> Option<ty::Region> {
             ast::expr_again(*) |
             ast::expr_ret(*) |
             ast::expr_log(*) |
-            ast::expr_assert(*) |
             ast::expr_while(*) |
             ast::expr_loop(*) |
             ast::expr_assign(*) |
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 0581f5f96b0..a6ccd69dd06 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -599,9 +599,6 @@ pub enum expr_ {
     expr_ret(Option<@expr>),
     expr_log(log_level, @expr, @expr),
 
-    /* just an assert */
-    expr_assert(@expr),
-
     expr_mac(mac),
 
     // A struct literal expression.
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index ea18598f75c..b8371c9e8d9 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -561,7 +561,6 @@ fn fold_field_(field: field, fld: @ast_fold) -> field {
                 fld.fold_expr(e)
             )
         }
-        expr_assert(e) => expr_assert(fld.fold_expr(e)),
         expr_mac(ref mac) => expr_mac(fold_mac((*mac))),
         expr_struct(path, ref fields, maybe_expr) => {
             expr_struct(
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index 4e1b34bb299..6f2d2c554aa 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -51,6 +51,7 @@ pub enum ObsoleteSyntax {
     ObsoleteTraitImplVisibility,
     ObsoleteRecordType,
     ObsoleteRecordPattern,
+    ObsoleteAssertion,
 }
 
 impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -155,6 +156,10 @@ fn obsolete(&self, sp: span, kind: ObsoleteSyntax) {
                 "structural record pattern",
                 "use a structure instead"
             ),
+            ObsoleteAssertion => (
+                "assertion",
+                "use `fail_unless!()` instead"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 0dba2bd45e1..384cf4f0e95 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -21,7 +21,7 @@
 use ast::{crate, crate_cfg, decl, decl_item};
 use ast::{decl_local, default_blk, deref, div, enum_def, enum_variant_kind};
 use ast::{expl, expr, expr_, expr_addr_of, expr_match, expr_again};
-use ast::{expr_assert, expr_assign, expr_assign_op, expr_binary, expr_block};
+use ast::{expr_assign, expr_assign_op, expr_binary, expr_block};
 use ast::{expr_break, expr_call, expr_cast, expr_copy, expr_do_body};
 use ast::{expr_field, expr_fn_block, expr_if, expr_index};
 use ast::{expr_lit, expr_log, expr_loop, expr_loop_body, expr_mac};
@@ -76,6 +76,7 @@
 use parse::obsolete::{ObsoleteTraitBoundSeparator, ObsoleteMutOwnedPointer};
 use parse::obsolete::{ObsoleteMutVector, ObsoleteTraitImplVisibility};
 use parse::obsolete::{ObsoleteRecordType, ObsoleteRecordPattern};
+use parse::obsolete::{ObsoleteAssertion};
 use parse::prec::{as_prec, token_to_binop};
 use parse::token::{can_begin_expr, is_ident, is_ident_or_path};
 use parse::token::{is_plain_ident, INTERPOLATED, special_idents};
@@ -1208,8 +1209,8 @@ fn parse_bottom_expr(&self) -> @expr {
             self.expect(&token::RPAREN);
         } else if self.eat_keyword(&~"assert") {
             let e = self.parse_expr();
-            ex = expr_assert(e);
-            hi = e.span.hi;
+            ex = expr_copy(e);  // whatever
+            self.obsolete(*self.last_span, ObsoleteAssertion);
         } else if self.eat_keyword(&~"return") {
             if can_begin_expr(&*self.token) {
                 let e = self.parse_expr();
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index d87238c720e..4a8176abc6f 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1427,10 +1427,6 @@ fn print_field(s: @ps, field: ast::field) {
           }
         }
       }
-      ast::expr_assert(expr) => {
-        word_nbsp(s, ~"assert");
-        print_expr(s, expr);
-      }
       ast::expr_mac(ref m) => print_mac(s, (*m)),
       ast::expr_paren(e) => {
           popen(s);
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 8b277b22149..6048256b90b 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -496,8 +496,7 @@ pub fn visit_expr<E>(ex: @expr, e: E, v: vt<E>) {
             (v.visit_expr)(b, e, v);
         }
         expr_addr_of(_, x) | expr_unary(_, x) |
-        expr_loop_body(x) | expr_do_body(x) |
-        expr_assert(x) => (v.visit_expr)(x, e, v),
+        expr_loop_body(x) | expr_do_body(x) => (v.visit_expr)(x, e, v),
         expr_lit(_) => (),
         expr_cast(x, t) => {
             (v.visit_expr)(x, e, v);