Add partial support for if expressions resulting in generic types

src/comp/middle/trans.rs

@@ -3046,11 +3046,14 @@ fn trans_if(@block_ctxt cx, @ast.expr cond,
 
             // If we have an else expression, then the entire
             // if expression can have a non-nil type.
-            // FIXME: Handle dynamic type sizes
             auto expr_ty = ty.expr_ty(elexpr);
-            expr_llty = type_of(else_res.bcx.fcx.ccx, expr_ty);
-            if (ty.type_is_structural(expr_ty)) {
-                expr_llty = T_ptr(expr_llty);
+            if (ty.type_has_dynamic_size(expr_ty)) {
+                expr_llty = T_typaram_ptr(cx.fcx.ccx.tn);
+            } else {
+                expr_llty = type_of(else_res.bcx.fcx.ccx, expr_ty);
+                if (ty.type_is_structural(expr_ty)) {
+                    expr_llty = T_ptr(expr_llty);
+                }
             }
         }
         case (_) {

src/test/run-pass/expr-if-generic.rs

@@ -0,0 +1,53 @@
+// xfail-boot
+// xfail-stage0
+// -*- rust -*-
+
+// Tests for if as expressions with dynamic type sizes
+
+type compare[T] = fn(&T t1, &T t2) -> bool;
+
+fn test_generic[T](&T expected, &T not_expected, &compare[T] eq) {
+  let T actual = if (true) { expected } else { not_expected };
+  check (eq(expected, actual));
+}
+
+fn test_bool() {
+  fn compare_bool(&bool b1, &bool b2) -> bool {
+    ret b1 == b2;
+  }
+  auto eq = bind compare_bool(_, _);
+  test_generic[bool](true, false, eq);
+}
+
+fn test_tup() {
+  type t = tup(int, int);
+  fn compare_tup(&t t1, &t t2) -> bool {
+    ret t1 == t2;
+  }
+  auto eq = bind compare_tup(_, _);
+  test_generic[t](tup(1, 2), tup(2, 3), eq);
+}
+
+fn test_vec() {
+  fn compare_vec(&vec[int] v1, &vec[int] v2) -> bool {
+    ret v1 == v2;
+  }
+  auto eq = bind compare_vec(_, _);
+  test_generic[vec[int]](vec(1, 2), vec(2, 3), eq);
+}
+
+fn test_box() {
+  fn compare_box(&@bool b1, &@bool b2) -> bool {
+    ret *b1 == *b2;
+  }
+  auto eq = bind compare_box(_, _);
+  test_generic[@bool](@true, @false, eq);
+}
+
+fn main() {
+  test_bool();
+  test_tup();
+  // FIXME: These two don't pass yet
+  test_vec();
+  test_box();
+}