Return Result instead of Option in alloc::Layout constructors

src/libstd/error.rs

@@ -57,7 +57,7 @@ use cell;
 use char;
 use core::array;
 use fmt::{self, Debug, Display};
-use heap::{AllocErr, CannotReallocInPlace};
+use heap::{AllocErr, LayoutErr, CannotReallocInPlace};
 use mem::transmute;
 use num;
 use str;
@@ -247,6 +247,15 @@ impl Error for AllocErr {
     }
 }
 
+#[unstable(feature = "allocator_api",
+           reason = "the precise API and guarantees it provides may be tweaked.",
+           issue = "32838")]
+impl Error for LayoutErr {
+    fn description(&self) -> &str {
+        "invalid parameters to Layout::from_size_align"
+    }
+}
+
 #[unstable(feature = "allocator_api",
            reason = "the precise API and guarantees it provides may be tweaked.",
            issue = "32838")]