improve liveness so it reports unused vars / dead assignments

doesn't warn about pattern bindings yet though

28 files changed, 327 insertions, 119 deletions

diff --git a/src/rustc/middle/liveness.rs b/src/rustc/middle/liveness.rs
index d95c58c15c8..25425e0e118 100644
--- a/src/rustc/middle/liveness.rs
+++ b/src/rustc/middle/liveness.rs
@@ -252,7 +252,7 @@ fn visit_fn(fk: visit::fn_kind, decl: fn_decl, body: blk,
     for decl.inputs.each { |arg|
         #debug["adding argument %d", arg.id];
         (*fn_maps).add_variable(arg.id, arg.ident);
-    }
+    };
 
     // gather up the various local variables, significant expressions,
     // and so forth:
@@ -278,7 +278,7 @@ fn visit_fn(fk: visit::fn_kind, decl: fn_decl, body: blk,
 
     // compute liveness
     let lsets = @liveness(fn_maps, specials);
-    let entry_ln = (*lsets).compute(body);
+    let entry_ln = (*lsets).compute(decl, body);
 
     // check for various error conditions
     let check_vt = visit::mk_vt(@{
@@ -290,6 +290,7 @@ fn visit_fn(fk: visit::fn_kind, decl: fn_decl, body: blk,
     check_vt.visit_block(body, lsets, check_vt);
     lsets.check_ret(id, sp, fk, entry_ln);
     lsets.check_fields(sp, entry_ln);
+    lsets.warn_about_unused_args(sp, decl, entry_ln);
 }
 
 fn add_class_fields(self: @ir_maps, did: def_id) {
@@ -384,11 +385,12 @@ fn visit_expr(expr: @expr, &&self: @ir_maps, vt: vt<@ir_maps>) {
 
 type users = {
     reader: live_node,
-    writer: live_node
+    writer: live_node,
+    used: bool
 };
 
 fn invalid_users() -> users {
-    {reader: invalid_node(), writer: invalid_node()}
+    {reader: invalid_node(), writer: invalid_node(), used: false}
 }
 
 type specials = {
@@ -400,6 +402,7 @@ type specials = {
 
 const ACC_READ: uint = 1u;
 const ACC_WRITE: uint = 2u;
+const ACC_USE: uint = 4u;
 
 class liveness {
     let tcx: ty::ctxt;
@@ -469,6 +472,15 @@ class liveness {
         }
     }
 
+    fn pat_bindings(pat: @pat, f: fn(live_node, variable, span)) {
+        let def_map = self.tcx.def_map;
+        pat_util::pat_bindings(def_map, pat) {|p_id, sp, _n|
+            let ln = self.live_node(p_id, sp);
+            let var = self.variable(p_id, sp);
+            f(ln, var, sp);
+        }
+    }
+
     fn idx(ln: live_node, var: variable) -> uint {
         *ln * self.ir.num_vars + *var
     }
@@ -487,6 +499,11 @@ class liveness {
         self.live_on_entry(self.successors[*ln], var)
     }
 
+    fn used_on_entry(ln: live_node, var: variable) -> bool {
+        assert ln.is_valid();
+        self.users[self.idx(ln, var)].used
+    }
+
     fn assigned_on_entry(ln: live_node, var: variable)
         -> option<live_node_kind> {
 
@@ -580,6 +597,10 @@ class liveness {
                                        self.users[idx].reader);
             changed |= copy_if_invalid(self.users[succ_idx].writer,
                                        self.users[idx].writer);
+            if self.users[succ_idx].used && !self.users[idx].used {
+                self.users[idx].used = true;
+                changed = true;
+            }
         }
 
         #debug["merge_from_succ(ln=%s, succ=%s, first_merge=%b, changed=%b)",
@@ -609,43 +630,39 @@ class liveness {
                idx, self.ln_str(writer)];
     }
 
-    // Indicates that a new value for the local variable was assigned.
-    fn write(writer: live_node, var: variable) {
-        let idx = self.idx(writer, var);
-        self.users[idx].reader = invalid_node();
-        self.users[idx].writer = writer;
-
-        #debug["%s writes %s (idx=%u): %s", writer.to_str(), var.to_str(),
-               idx, self.ln_str(writer)];
-    }
-
-    // Indicates that the current value of the local variable was used.
-    fn read(reader: live_node, var: variable) {
-        let idx = self.idx(reader, var);
-        self.users[idx].reader = reader;
-
-        #debug["%s reads %s (idx=%u): %s", reader.to_str(), var.to_str(),
-               idx, self.ln_str(reader)];
-    }
-
     // Either read, write, or both depending on the acc bitset
     fn acc(ln: live_node, var: variable, acc: uint) {
-        if (acc & ACC_WRITE) != 0u { self.write(ln, var) }
+        let idx = self.idx(ln, var);
+        let user = &mut self.users[idx];
+
+        if (acc & ACC_WRITE) != 0u {
+            user.reader = invalid_node();
+            user.writer = ln;
+        }
 
         // Important: if we both read/write, must do read second
         // or else the write will override.
-        if (acc & ACC_READ) != 0u { self.read(ln, var) }
+        if (acc & ACC_READ) != 0u {
+            user.reader = ln;
+        }
+
+        if (acc & ACC_USE) != 0u {
+            self.users[idx].used = true;
+        }
+
+        #debug["%s accesses[%x] %s: %s",
+               ln.to_str(), acc, var.to_str(), self.ln_str(ln)];
     }
 
     // _______________________________________________________________________
 
-    fn compute(body: blk) -> live_node {
+    fn compute(decl: fn_decl, body: blk) -> live_node {
         // if there is a `break` or `cont` at the top level, then it's
         // effectively a return---this only occurs in `for` loops,
         // where the body is really a closure.
         let entry_ln: live_node =
             self.with_loop_nodes(self.s.exit_ln, self.s.exit_ln) {||
-                self.propagate_through_fn_block(body)
+                self.propagate_through_fn_block(decl, body)
             };
 
         // hack to skip the loop unless #debug is enabled:
@@ -661,14 +678,28 @@ class liveness {
         entry_ln
     }
 
-    fn propagate_through_fn_block(blk: blk) -> live_node {
-        if blk.node.expr.is_none() {
-            self.read(self.s.fallthrough_ln, self.s.no_ret_var)
+    fn propagate_through_fn_block(decl: fn_decl, blk: blk) -> live_node {
+        // inputs passed by & mode should be considered live on exit:
+        for decl.inputs.each { |arg|
+            alt ty::resolved_mode(self.tcx, arg.mode) {
+              by_mutbl_ref {
+                let var = self.variable(arg.id, blk.span);
+                self.acc(self.s.exit_ln, var, ACC_READ);
+              }
+              by_val | by_ref | by_move | by_copy {}
+            }
         }
 
         // in a ctor, there is an implicit use of self.f for all fields f:
         for self.ir.field_map.each_value { |var|
-            self.read(self.s.fallthrough_ln, var);
+            self.acc(self.s.exit_ln, var, ACC_READ|ACC_USE);
+        }
+
+        // the fallthrough exit is only for those cases where we do not
+        // explicitly return:
+        self.init_from_succ(self.s.fallthrough_ln, self.s.exit_ln);
+        if blk.node.expr.is_none() {
+            self.acc(self.s.fallthrough_ln, self.s.no_ret_var, ACC_READ)
         }
 
         self.propagate_through_block(blk, self.s.fallthrough_ln)
@@ -723,10 +754,7 @@ class liveness {
 
         let opt_init = local.node.init.map { |i| i.expr };
         let mut succ = self.propagate_through_opt_expr(opt_init, succ);
-        let def_map = self.tcx.def_map;
-        pat_util::pat_bindings(def_map, local.node.pat) { |p_id, sp, _n|
-            let ln = self.live_node(p_id, sp);
-            let var = self.variable(p_id, sp);
+        self.pat_bindings(local.node.pat) { |ln, var, _sp|
             self.init_from_succ(ln, succ);
             self.define(ln, var);
             succ = ln;
@@ -752,7 +780,7 @@ class liveness {
           // Interesting cases with control flow or which gen/kill
 
           expr_path(_) {
-            self.access_path(expr, succ, ACC_READ)
+            self.access_path(expr, succ, ACC_READ | ACC_USE)
           }
 
           expr_field(e, nm, _) {
@@ -763,7 +791,7 @@ class liveness {
             alt self.as_self_field(e, nm) {
               some((ln, var)) {
                 self.init_from_succ(ln, succ);
-                self.read(ln, var);
+                self.acc(ln, var, ACC_READ | ACC_USE);
                 ln
               }
               none {
@@ -779,7 +807,7 @@ class liveness {
             (*caps).foldr(succ) { |cap, succ|
                 self.init_from_succ(cap.ln, succ);
                 let var = self.variable_from_rdef(cap.rv, expr.span);
-                self.read(cap.ln, var);
+                self.acc(cap.ln, var, ACC_READ | ACC_USE);
                 cap.ln
             }
           }
@@ -877,8 +905,14 @@ class liveness {
           expr_swap(l, r) {
             // see comment on lvalues in
             // propagate_through_lvalue_components()
-            let succ = self.write_lvalue(r, succ, ACC_WRITE|ACC_READ);
-            let succ = self.write_lvalue(l, succ, ACC_WRITE|ACC_READ);
+
+            // I count swaps as `used` cause it might be something like:
+            //    foo.bar <-> x
+            // and I am too lazy to distinguish this case from
+            //    y <-> x
+            // (where both x, y are unused) just for a warning.
+            let succ = self.write_lvalue(r, succ, ACC_WRITE|ACC_READ|ACC_USE);
+            let succ = self.write_lvalue(l, succ, ACC_WRITE|ACC_READ|ACC_USE);
             let succ = self.propagate_through_lvalue_components(r, succ);
             self.propagate_through_lvalue_components(l, succ)
           }
@@ -1205,28 +1239,35 @@ class liveness {
 
 fn check_local(local: @local, &&self: @liveness, vt: vt<@liveness>) {
     alt local.node.init {
-      some({op: init_move, expr: expr}) {
-        // can never be accessed uninitialized, but the move might
-        // be invalid
-        #debug["check_local() with move initializer"];
-        self.check_move_from_expr(expr, vt);
-      }
-      some({op: init_op, expr: _}) {
-        // can never be accessed uninitialized
-        #debug["check_local() with initializer"];
+      some({op: op, expr: expr}) {
+
+        // Initializer:
+
+        alt op {
+          init_move {self.check_move_from_expr(expr, vt)}
+          init_assign {}
+        }
+        self.warn_about_unused_or_dead_vars_in_pat(local.node.pat);
+        if !local.node.is_mutbl {
+            self.check_for_reassignments_in_pat(local.node.pat);
+        }
       }
       none {
+
+        // No initializer: the variable might be unused; if not, it
+        // should not be live at this point.
+
         #debug["check_local() with no initializer"];
-        let def_map = self.tcx.def_map;
-        pat_util::pat_bindings(def_map, local.node.pat) {|p_id, sp, _n|
-            let ln = (*self).live_node(p_id, sp);
-            let var = (*self).variable(p_id, sp);
-            alt (*self).live_on_exit(ln, var) {
-              none { /* not live: good */ }
-              some(lnk) {
-                self.report_illegal_read(
-                    local.span, lnk, var, possibly_uninitialized_variable);
-              }
+        (*self).pat_bindings(local.node.pat) { |ln, var, sp|
+            if !self.warn_about_unused(sp, ln, var) {
+                alt (*self).live_on_exit(ln, var) {
+                  none { /* not live: good */ }
+                  some(lnk) {
+                    self.report_illegal_read(
+                        local.span, lnk, var,
+                        possibly_uninitialized_variable);
+                  }
+                }
             }
         }
       }
@@ -1262,11 +1303,21 @@ fn check_expr(expr: @expr, &&self: @liveness, vt: vt<@liveness>) {
       expr_assign(l, r) {
         self.check_lvalue(l, vt);
         vt.visit_expr(r, self, vt);
+
+        visit::visit_expr(expr, self, vt);
       }
 
       expr_move(l, r) {
         self.check_lvalue(l, vt);
         self.check_move_from_expr(r, vt);
+
+        visit::visit_expr(expr, self, vt);
+      }
+
+      expr_assign_op(_, l, _) {
+        self.check_lvalue(l, vt);
+
+        visit::visit_expr(expr, self, vt);
       }
 
       expr_call(f, args, _) {
@@ -1293,7 +1344,7 @@ fn check_expr(expr: @expr, &&self: @liveness, vt: vt<@liveness>) {
       expr_assert(*) | expr_check(*) | expr_addr_of(*) | expr_copy(*) |
       expr_loop_body(*) | expr_cast(*) | expr_unary(*) | expr_fail(*) |
       expr_ret(*) | expr_break | expr_cont | expr_lit(_) |
-      expr_block(*) | expr_swap(*) | expr_assign_op(*) | expr_mac(*) {
+      expr_block(*) | expr_swap(*) | expr_mac(*) {
         visit::visit_expr(expr, self, vt);
       }
     }
@@ -1434,32 +1485,20 @@ impl check_methods for @liveness {
                 // only legal if there is no later assignment.
                 let ln = (*self).live_node(expr.id, expr.span);
                 let var = (*self).variable(nid, expr.span);
-                alt (*self).assigned_on_exit(ln, var) {
-                  some(lnk_expr(span)) {
-                    self.tcx.sess.span_err(
-                        span,
-                        "re-assignment of immutable variable");
-
-                    self.tcx.sess.span_note(
-                        expr.span,
-                        "prior assignment occurs here");
+                self.check_for_reassignment(ln, var, expr.span);
+                self.warn_about_dead_assign(expr.span, ln, var);
+              }
+              def {
+                alt relevant_def(def) {
+                  some(rdef_var(nid)) {
+                    let ln = (*self).live_node(expr.id, expr.span);
+                    let var = (*self).variable(nid, expr.span);
+                    self.warn_about_dead_assign(expr.span, ln, var);
                   }
-                  some(lnk) {
-                    self.tcx.sess.span_bug(
-                        expr.span,
-                        #fmt["illegal writer: %?", lnk]);
-                   }
+                  some(rdef_self) {}
                   none {}
                 }
               }
-              def_arg(*) | def_local(_, true) {
-                // Assignment to a mutable variable; no conditions
-                // req'd.  In the case of arguments, the mutability is
-                // enforced by borrowck.
-              }
-              _ {
-                // Not a variable, don't care
-              }
             }
           }
 
@@ -1471,6 +1510,33 @@ impl check_methods for @liveness {
        }
     }
 
+    fn check_for_reassignments_in_pat(pat: @pat) {
+        (*self).pat_bindings(pat) { |ln, var, sp|
+            self.check_for_reassignment(ln, var, sp);
+        }
+    }
+
+    fn check_for_reassignment(ln: live_node, var: variable,
+                              orig_span: span) {
+        alt (*self).assigned_on_exit(ln, var) {
+          some(lnk_expr(span)) {
+            self.tcx.sess.span_err(
+                span,
+                "re-assignment of immutable variable");
+
+            self.tcx.sess.span_note(
+                orig_span,
+                "prior assignment occurs here");
+          }
+          some(lnk) {
+            self.tcx.sess.span_bug(
+                orig_span,
+                #fmt["illegal writer: %?", lnk]);
+          }
+          none {}
+        }
+    }
+
     fn report_illegal_read(chk_span: span,
                            lnk: live_node_kind,
                            var: variable,
@@ -1499,4 +1565,62 @@ impl check_methods for @liveness {
           }
         }
     }
-}
\ No newline at end of file
+
+    fn should_warn(var: variable) -> option<str> {
+        let name = self.ir.var_infos[*var].name;
+        if name[0] == ('_' as u8) {none} else {some(name)}
+    }
+
+    fn warn_about_unused_args(sp: span, decl: fn_decl, entry_ln: live_node) {
+        for decl.inputs.each { |arg|
+            let var = (*self).variable(arg.id, arg.ty.span);
+            alt ty::resolved_mode(self.tcx, arg.mode) {
+              by_mutbl_ref {
+                // for mutable reference arguments, something like
+                //    x = 1;
+                // is not worth warning about, as it has visible
+                // side effects outside the fn.
+                alt (*self).assigned_on_entry(entry_ln, var) {
+                  some(_) { /*ok*/ }
+                  none {
+                    // but if it is not written, it ought to be used
+                    self.warn_about_unused(sp, entry_ln, var);
+                  }
+                }
+              }
+              by_val | by_ref | by_move | by_copy {
+                self.warn_about_unused(sp, entry_ln, var);
+              }
+            }
+        }
+    }
+
+    fn warn_about_unused_or_dead_vars_in_pat(pat: @pat) {
+        (*self).pat_bindings(pat) { |ln, var, sp|
+            if !self.warn_about_unused(sp, ln, var) {
+                self.warn_about_dead_assign(sp, ln, var);
+            }
+        }
+    }
+
+    fn warn_about_unused(sp: span, ln: live_node, var: variable) -> bool {
+        if !(*self).used_on_entry(ln, var) {
+            for self.should_warn(var).each { |name|
+                self.tcx.sess.span_warn(
+                    sp, #fmt["unused variable: `%s`", name]);
+            }
+            ret true;
+        }
+        ret false;
+    }
+
+    fn warn_about_dead_assign(sp: span, ln: live_node, var: variable) {
+        if (*self).live_on_exit(ln, var).is_none() {
+            for self.should_warn(var).each { |name|
+                self.tcx.sess.span_warn(
+                    sp,
+                    #fmt["value assigned to `%s` is never read", name]);
+            }
+        }
+    }
+ }
\ No newline at end of file
diff --git a/src/test/compile-fail/assign-imm-local-twice.rs b/src/test/compile-fail/assign-imm-local-twice.rs
index 13ec17e0585..7472ebe7eff 100644
--- a/src/test/compile-fail/assign-imm-local-twice.rs
+++ b/src/test/compile-fail/assign-imm-local-twice.rs
@@ -1,9 +1,10 @@
-fn test(cond: bool) {
+fn test() {
     let v: int;
     v = 1; //! NOTE prior assignment occurs here
+    #debug["v=%d", v];
     v = 2; //! ERROR re-assignment of immutable variable
+    #debug["v=%d", v];
 }
 
 fn main() {
-    test(true);
 }
diff --git a/src/test/compile-fail/borrowck-pat-reassign-binding.rs b/src/test/compile-fail/borrowck-pat-reassign-binding.rs
index e2c41aaa1df..5018d4835ae 100644
--- a/src/test/compile-fail/borrowck-pat-reassign-binding.rs
+++ b/src/test/compile-fail/borrowck-pat-reassign-binding.rs
@@ -11,4 +11,5 @@ fn main() {
         x = some(i+1); //! ERROR assigning to mutable local variable prohibited due to outstanding loan
       }
     }
+    copy x; // just to prevent liveness warnings
 }
diff --git a/src/test/compile-fail/borrowck-pat-reassign-sometimes-binding.rs b/src/test/compile-fail/borrowck-pat-reassign-sometimes-binding.rs
index 2fc9b5b5153..bf28af2db4d 100644
--- a/src/test/compile-fail/borrowck-pat-reassign-sometimes-binding.rs
+++ b/src/test/compile-fail/borrowck-pat-reassign-sometimes-binding.rs
@@ -14,4 +14,5 @@ fn main() {
         x = some(1); //! ERROR assigning to mutable local variable prohibited due to outstanding loan
       }
     }
+    copy x; // just to prevent liveness warnings
 }
diff --git a/src/test/compile-fail/liveness-assign-imm-local-in-loop.rs b/src/test/compile-fail/liveness-assign-imm-local-in-loop.rs
index a68528418e6..2fc1bca5a63 100644
--- a/src/test/compile-fail/liveness-assign-imm-local-in-loop.rs
+++ b/src/test/compile-fail/liveness-assign-imm-local-in-loop.rs
@@ -1,11 +1,11 @@
-fn test(cond: bool) {
+fn test() {
     let v: int;
     loop {
         v = 1; //! ERROR re-assignment of immutable variable
         //!^ NOTE prior assignment occurs here
+        copy v; // just to prevent liveness warnings
     }
 }
 
 fn main() {
-    test(true);
 }
diff --git a/src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs b/src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs
index 2f880e03c74..adb42333523 100644
--- a/src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs
+++ b/src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs
@@ -1,9 +1,9 @@
-fn test(cond: bool) {
+fn test() {
     let v: int;
     v = 2;  //! NOTE prior assignment occurs here
     v += 1; //! ERROR re-assignment of immutable variable
+    copy v;
 }
 
 fn main() {
-    test(true);
 }
diff --git a/src/test/compile-fail/liveness-assign-imm-local-with-init.rs b/src/test/compile-fail/liveness-assign-imm-local-with-init.rs
new file mode 100644
index 00000000000..045ce5baa46
--- /dev/null
+++ b/src/test/compile-fail/liveness-assign-imm-local-with-init.rs
@@ -0,0 +1,9 @@
+fn test() {
+    let v: int = 1; //! NOTE prior assignment occurs here
+    copy v;
+    v = 2; //! ERROR re-assignment of immutable variable
+    copy v;
+}
+
+fn main() {
+}
diff --git a/src/test/compile-fail/liveness-break-uninit-2.rs b/src/test/compile-fail/liveness-break-uninit-2.rs
index 30038dbe96e..4b18845f878 100644
--- a/src/test/compile-fail/liveness-break-uninit-2.rs
+++ b/src/test/compile-fail/liveness-break-uninit-2.rs
@@ -1,9 +1,7 @@
 fn foo() -> int {
     let x: int;
-    let i: int;
 
     while 1 != 2  {
-        i = 0;
         break;
         x = 0; //! WARNING unreachable statement
     }
diff --git a/src/test/compile-fail/liveness-break-uninit.rs b/src/test/compile-fail/liveness-break-uninit.rs
index 55041daa7fb..5bba9535e53 100644
--- a/src/test/compile-fail/liveness-break-uninit.rs
+++ b/src/test/compile-fail/liveness-break-uninit.rs
@@ -1,9 +1,7 @@
 fn foo() -> int {
     let x: int;
-    let i: int;
 
     loop {
-        i = 0;
         break;
         x = 0;  //! WARNING unreachable statement
     }
diff --git a/src/test/compile-fail/liveness-dead.rs b/src/test/compile-fail/liveness-dead.rs
new file mode 100644
index 00000000000..bda153b5ad4
--- /dev/null
+++ b/src/test/compile-fail/liveness-dead.rs
@@ -0,0 +1,20 @@
+fn f1(&x: int) {
+    x = 1; // no error
+}
+
+fn f2() {
+    let mut x = 3; //! WARNING value assigned to `x` is never read
+    x = 4;
+    copy x;
+}
+
+fn f3() {
+    let mut x = 3;
+    copy x;
+    x = 4; //! WARNING value assigned to `x` is never read
+}
+
+fn main() { // leave this in here just to trigger compile-fail:
+    let x: int;
+    copy x; //! ERROR use of possibly uninitialized variable: `x`
+}
diff --git a/src/test/compile-fail/liveness-init-in-fru.rs b/src/test/compile-fail/liveness-init-in-fru.rs
index 1c17a2503dc..a9a80e9ad6e 100644
--- a/src/test/compile-fail/liveness-init-in-fru.rs
+++ b/src/test/compile-fail/liveness-init-in-fru.rs
@@ -5,4 +5,5 @@ type point = {x: int, y: int};
 fn main() {
     let mut origin: point;
     origin = {x: 10 with origin}; //! ERROR use of possibly uninitialized variable: `origin`
+    copy origin;
 }
diff --git a/src/test/compile-fail/liveness-init-op-equal.rs b/src/test/compile-fail/liveness-init-op-equal.rs
index 2f37dc5070f..8d397e73b1f 100644
--- a/src/test/compile-fail/liveness-init-op-equal.rs
+++ b/src/test/compile-fail/liveness-init-op-equal.rs
@@ -1,8 +1,8 @@
-fn test(cond: bool) {
+fn test() {
     let v: int;
     v += 1; //! ERROR use of possibly uninitialized variable: `v`
+    copy v;
 }
 
 fn main() {
-    test(true);
 }
diff --git a/src/test/compile-fail/liveness-init-plus-equal.rs b/src/test/compile-fail/liveness-init-plus-equal.rs
index 56c5b3b2717..dacc1f4f922 100644
--- a/src/test/compile-fail/liveness-init-plus-equal.rs
+++ b/src/test/compile-fail/liveness-init-plus-equal.rs
@@ -1,8 +1,8 @@
-fn test(cond: bool) {
+fn test() {
     let mut v: int;
     v = v + 1; //! ERROR use of possibly uninitialized variable: `v`
+    copy v;
 }
 
 fn main() {
-    test(true);
 }
diff --git a/src/test/compile-fail/liveness-issue-2163.rs b/src/test/compile-fail/liveness-issue-2163.rs
index dea27e585ef..6045a137a9e 100644
--- a/src/test/compile-fail/liveness-issue-2163.rs
+++ b/src/test/compile-fail/liveness-issue-2163.rs
@@ -1,5 +1,5 @@
-fn main(s: [str]) {
+fn main(_s: [str]) {
     let a: [int] = [];
-    vec::each(a) { |x| //! ERROR not all control paths return a value
+    vec::each(a) { |_x| //! ERROR not all control paths return a value
     }
 }
diff --git a/src/test/compile-fail/liveness-move-from-mode.rs b/src/test/compile-fail/liveness-move-from-mode.rs
index 01483f033eb..f0db4926734 100644
--- a/src/test/compile-fail/liveness-move-from-mode.rs
+++ b/src/test/compile-fail/liveness-move-from-mode.rs
@@ -1,4 +1,4 @@
-fn take(-x: int) {}
+fn take(-_x: int) {}
 
 fn main() {
 
diff --git a/src/test/compile-fail/liveness-move-in-loop.rs b/src/test/compile-fail/liveness-move-in-loop.rs
index 81467d8a2b4..1bdfc392bd9 100644
--- a/src/test/compile-fail/liveness-move-in-loop.rs
+++ b/src/test/compile-fail/liveness-move-in-loop.rs
@@ -9,6 +9,8 @@ fn main() {
                 loop {
                     x <- y; //! ERROR use of moved variable
                     //!^ NOTE move of variable occurred here
+
+                    copy x;
                 }
             }
         }
diff --git a/src/test/compile-fail/liveness-move-in-while.rs b/src/test/compile-fail/liveness-move-in-while.rs
index 6acbc5a9f35..d5a95b08bd8 100644
--- a/src/test/compile-fail/liveness-move-in-while.rs
+++ b/src/test/compile-fail/liveness-move-in-while.rs
@@ -4,7 +4,7 @@ fn main() {
     let mut x: int;
     loop {
         log(debug, y);
-        while true { while true { while true { x <- y; } } }
+        while true { while true { while true { x <- y; copy x; } } }
         //!^ ERROR use of moved variable: `y`
         //!^^ NOTE move of variable occurred here
     }
diff --git a/src/test/compile-fail/liveness-swap-uninit.rs b/src/test/compile-fail/liveness-swap-uninit.rs
index 53714c1f740..d3a5395bfff 100644
--- a/src/test/compile-fail/liveness-swap-uninit.rs
+++ b/src/test/compile-fail/liveness-swap-uninit.rs
@@ -1,5 +1,6 @@
 fn main() {
-	let x = 3;
-	let y;
-	x <-> y; //! ERROR use of possibly uninitialized variable: `y`
+    let mut x = 3;
+    let y;
+    x <-> y; //! ERROR use of possibly uninitialized variable: `y`
+    copy x;
 }
diff --git a/src/test/compile-fail/liveness-uninit-after-item.rs b/src/test/compile-fail/liveness-uninit-after-item.rs
index 7c619804c3c..3d8e77040cd 100644
--- a/src/test/compile-fail/liveness-uninit-after-item.rs
+++ b/src/test/compile-fail/liveness-uninit-after-item.rs
@@ -1,6 +1,6 @@
 fn main() {
     let bar;
-    fn baz(x: int) { }
+    fn baz(_x: int) { }
     bind baz(bar); //! ERROR use of possibly uninitialized variable: `bar`
 }
 
diff --git a/src/test/compile-fail/liveness-unused.rs b/src/test/compile-fail/liveness-unused.rs
new file mode 100644
index 00000000000..2a19c9808c7
--- /dev/null
+++ b/src/test/compile-fail/liveness-unused.rs
@@ -0,0 +1,50 @@
+fn f1(x: int) {
+    //!^ WARNING unused variable: `x`
+    //!^^ WARNING unused variable x
+    // (the 2nd one is from tstate)
+}
+
+fn f1b(&x: int) {
+    //!^ WARNING unused variable: `x`
+    //!^^ WARNING unused variable x
+    // (the 2nd one is from tstate)
+}
+
+fn f2() {
+    let x = 3;
+    //!^ WARNING unused variable: `x`
+    //!^^ WARNING unused variable x
+    // (the 2nd one is from tstate)
+}
+
+fn f3() {
+    let mut x = 3;
+    //!^ WARNING unused variable: `x`
+    x += 4;
+    //!^ WARNING value assigned to `x` is never read
+}
+
+fn f3b() {
+    let mut z = 3;
+    //!^ WARNING unused variable: `z`
+    loop {
+        z += 4;
+    }
+}
+
+fn f4() {
+    alt some(3) {
+      some(i) {
+      }
+      none {}
+    }
+}
+
+// leave this in here just to trigger compile-fail:
+pure fn is_even(i: int) -> bool { (i%2) == 0 }
+fn even(i: int) : is_even(i) -> int { i }
+fn main() {
+    let i: int = 4;
+    log(debug, false && { check is_even(i); true });
+    even(i); //! ERROR unsatisfied precondition
+}
diff --git a/src/test/compile-fail/liveness-use-after-move.rs b/src/test/compile-fail/liveness-use-after-move.rs
index 48d7a9a303e..34a932a5a16 100644
--- a/src/test/compile-fail/liveness-use-after-move.rs
+++ b/src/test/compile-fail/liveness-use-after-move.rs
@@ -2,4 +2,5 @@ fn main() {
     let x = @5;
     let y <- x; //! NOTE move of variable occurred here
     log(debug, *x); //! ERROR use of moved variable: `x`
+    copy y;
 }
diff --git a/src/test/compile-fail/liveness-use-after-send.rs b/src/test/compile-fail/liveness-use-after-send.rs
index 63e42bee3c9..3827598c0a7 100644
--- a/src/test/compile-fail/liveness-use-after-send.rs
+++ b/src/test/compile-fail/liveness-use-after-send.rs
@@ -8,7 +8,7 @@ enum _chan<T> = int;
 
 // Tests that "log(debug, message);" is flagged as using
 // message after the send deinitializes it
-fn test00_start(ch: _chan<int>, message: int, count: int) {
+fn test00_start(ch: _chan<int>, message: int, _count: int) {
     send(ch, message); //! NOTE move of variable occurred here
     log(debug, message); //! ERROR use of moved variable: `message`
 }
diff --git a/src/test/compile-fail/no-constraint-prop.rs b/src/test/compile-fail/no-constraint-prop.rs
index ec7f8076892..f1c02bd406f 100644
--- a/src/test/compile-fail/no-constraint-prop.rs
+++ b/src/test/compile-fail/no-constraint-prop.rs
@@ -2,9 +2,9 @@
 
 fn main() unsafe {
     fn foo(_a: uint, _b: uint) : uint::le(_a, _b) {}
-    let a: uint = 1u;
-    let b: uint = 4u;
-    let c: uint = 5u;
+    let mut a: uint = 1u;
+    let mut b: uint = 4u;
+    let mut c: uint = 5u;
     // make sure that the constraint le(b, a) exists...
     check (uint::le(b, a));
     // ...invalidate it...
diff --git a/src/test/compile-fail/pred-assign.rs b/src/test/compile-fail/pred-assign.rs
index 8a7810cabb0..19a71050986 100644
--- a/src/test/compile-fail/pred-assign.rs
+++ b/src/test/compile-fail/pred-assign.rs
@@ -7,9 +7,9 @@ fn f(a: int, b: int) : lt(a, b) { }
 pure fn lt(a: int, b: int) -> bool { ret a < b; }
 
 fn main() {
-    let a: int = 10;
-    let b: int = 23;
-    let c: int = 77;
+    let mut a: int = 10;
+    let mut b: int = 23;
+    let mut c: int = 77;
     check (lt(a, b));
     a = 24;
     f(a, b);
diff --git a/src/test/compile-fail/pred-swap.rs b/src/test/compile-fail/pred-swap.rs
index 3f506edc8a6..b62f5a942f7 100644
--- a/src/test/compile-fail/pred-swap.rs
+++ b/src/test/compile-fail/pred-swap.rs
@@ -7,9 +7,9 @@ fn f(a: int, b: int) : lt(a, b) { }
 pure fn lt(a: int, b: int) -> bool { ret a < b; }
 
 fn main() {
-    let a: int = 10;
-    let b: int = 23;
-    let c: int = 77;
+    let mut a: int = 10;
+    let mut b: int = 23;
+    let mut c: int = 77;
     check (lt(a, b));
     b <-> a;
     f(a, b);
diff --git a/src/test/compile-fail/tstate-fru.rs b/src/test/compile-fail/tstate-fru.rs
index a4989d86ab4..70c39d434ff 100644
--- a/src/test/compile-fail/tstate-fru.rs
+++ b/src/test/compile-fail/tstate-fru.rs
@@ -10,4 +10,5 @@ fn main() {
     origin = {x: 0, y: 0};
     let right: point = {x: 10 with tested(origin)};
         //!^ ERROR precondition
+    copy right;
 }
diff --git a/src/test/compile-fail/tstate-while-loop-unsat-constriants.rs b/src/test/compile-fail/tstate-while-loop-unsat-constriants.rs
index 646d2466c74..5fff9aa9cb5 100644
--- a/src/test/compile-fail/tstate-while-loop-unsat-constriants.rs
+++ b/src/test/compile-fail/tstate-while-loop-unsat-constriants.rs
@@ -6,8 +6,8 @@ pure fn even(y: int) -> bool { true }
 
 fn main() {
 
-    let y: int = 42;
-    let x: int = 1;
+    let mut y: int = 42;
+    let mut x: int = 1;
     check (even(y));
     loop {
         print_even(y);
diff --git a/src/test/compile-fail/unsafe-alt.rs b/src/test/compile-fail/unsafe-alt.rs
index 92aa4ac00a4..498508d8980 100644
--- a/src/test/compile-fail/unsafe-alt.rs
+++ b/src/test/compile-fail/unsafe-alt.rs
@@ -3,6 +3,6 @@
 enum foo { left({mut x: int}), right(bool) }
 
 fn main() {
-    let x = left({mut x: 10});
-    alt x { left(i) { x = right(false); log(debug, i); } _ { } }
+    let mut x = left({mut x: 10});
+    alt x { left(i) { x = right(false); copy x; log(debug, i); } _ { } }
 }