parse: typeck: enabling trivial casts of tail-call return values

introduces ctypes::m_* machine type aliases for int, uint, float
depending on cfg(target_arch) that are used in tests

src/comp/middle/trans.rs

@@ -4088,10 +4088,8 @@ fn trans_expr(bcx: @block_ctxt, e: @ast::expr, dest: dest) -> @block_ctxt {
       }
       ast::expr_cast(val, _) {
         alt tcx.cast_map.find(e.id) {
-          option::none. { ret trans_cast(bcx, val, e.id, dest); }
-          some { alt option::get(some) {
-            ty::triv_cast. { ret trans_expr(bcx, val, dest); }
-          } }
+          some(ty::triv_cast.) { ret trans_expr(bcx, val, dest); }
+          _ { ret trans_cast(bcx, val, e.id, dest); }
         }
       }
       ast::expr_anon_obj(anon_obj) {
@@ -4122,7 +4120,7 @@ fn trans_expr(bcx: @block_ctxt, e: @ast::expr, dest: dest) -> @block_ctxt {
         // that is_call_expr(ex) -- but we don't support that
         // yet
         // FIXME
-        check (ast_util::is_call_expr(ex));
+        check (ast_util::is_tail_call_expr(ex));
         ret trans_be(bcx, ex);
       }
       ast::expr_fail(expr) {
@@ -4455,7 +4453,8 @@ fn trans_ret(bcx: @block_ctxt, e: option::t<@ast::expr>) -> @block_ctxt {
 fn build_return(bcx: @block_ctxt) { Br(bcx, bcx_fcx(bcx).llreturn); }
 
 // fn trans_be(cx: &@block_ctxt, e: &@ast::expr) -> result {
-fn trans_be(cx: @block_ctxt, e: @ast::expr) : ast_util::is_call_expr(e) ->
+fn trans_be(cx: @block_ctxt, e: @ast::expr) :
+ast_util::is_tail_call_expr(e) ->
    @block_ctxt {
     // FIXME: Turn this into a real tail call once
     // calling convention issues are settled

src/comp/middle/ty.rs

@@ -1501,7 +1501,7 @@ fn eq_ty(&&a: t, &&b: t) -> bool { ret a == b; }
 // Convert type to machine type
 // (i.e. replace uint, int, float with target architecture machine types)
 //
-// Somewhat expensive but casts that need this should be rare
+// FIXME somewhat expensive but this should only be called rarely
 fn ty_to_machine_ty(cx: ctxt, ty: t) -> t {
     fn sub_fn(cx: ctxt, uint_ty: t, int_ty: t, float_ty: t, in: t) -> t {
         alt struct(cx, in) {
@@ -1525,12 +1525,9 @@ fn ty_to_machine_ty(cx: ctxt, ty: t) -> t {
 // equal or if they are equal after substituting all occurences of
 //  machine independent primitive types by their machine type equivalents
 // for the current target architecture
-//
-// Somewhat expensive but casts that need this should be rare
 fn triv_eq_ty(cx: ctxt, &&a: t, &&b: t) -> bool {
-    let mach_a = ty_to_machine_ty(cx, a);
-    let mach_b = ty_to_machine_ty(cx, b );
-    ret eq_ty(a, b) || eq_ty(mach_a, mach_b);
+    ret eq_ty(a, b)
+        || eq_ty(ty_to_machine_ty(cx, a), ty_to_machine_ty(cx, b));
 }
 
 // Type lookups

src/comp/middle/typeck.rs

@@ -1846,8 +1846,21 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
       }
       ast::expr_be(e) {
         // FIXME: prove instead of assert
-        assert (ast_util::is_call_expr(e));
+        assert (ast_util::is_tail_call_expr(e));
         check_expr_with(fcx, e, fcx.ret_ty);
+
+        alt e.node {
+          ast::expr_cast(_, _) {
+            alt tcx.cast_map.find(e.id) {
+              option::some(ty::triv_cast.) { }
+              _ { tcx.sess.span_err(expr.span,
+                    "non-trivial cast of tail-call return value");
+                }
+            }
+          }
+          _ { /* regular tail call */ }
+        }
+
         bot = true;
         write::nil_ty(tcx, id);
       }
@@ -2112,8 +2125,10 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
                                   ty_to_str(tcx, t_1));
         }
 
+        // mark as triv_cast for later dropping in trans
         if ty::triv_eq_ty(tcx, t_1, t_e)
             { tcx.cast_map.insert(expr.id, ty::triv_cast); }
+
         write::ty_only_fixup(fcx, id, t_1);
       }
       ast::expr_vec(args, mut) {

src/comp/syntax/ast_util.rs

@@ -175,6 +175,14 @@ pure fn is_call_expr(e: @expr) -> bool {
     alt e.node { expr_call(_, _, _) { true } _ { false } }
 }
 
+pure fn is_tail_call_expr(e: @expr) -> bool {
+    alt e.node {
+      expr_call(_, _, _) { true }
+      expr_cast(inner_e, _) { is_call_expr(inner_e) }
+      _ { false }
+    }
+}
+
 fn is_constraint_arg(e: @expr) -> bool {
     alt e.node {
       expr_lit(_) { ret true; }

src/comp/syntax/parse/parser.rs

@@ -962,7 +962,7 @@ fn parse_bottom_expr(p: parser) -> @ast::expr {
         let e = parse_expr(p);
 
         // FIXME: Is this the right place for this check?
-        if /*check*/ast_util::is_call_expr(e) {
+        if /*check*/ ast_util::is_tail_call_expr(e) {
             hi = e.span.hi;
             ex = ast::expr_be(e);
         } else { p.fatal("Non-call expression in tail call"); }