librustc: Make the compiler ignore purity.

For bootstrapping purposes, this commit does not remove all uses of
the keyword "pure" -- doing so would cause the compiler to no longer
bootstrap due to some syntax extensions ("deriving" in particular).
Instead, it makes the compiler ignore "pure". Post-snapshot, we can
remove "pure" from the language.

There are quite a few (~100) borrow check errors that were essentially
all the result of mutable fields or partial borrows of `@mut`. Per
discussions with Niko I think we want to allow partial borrows of
`@mut` but detect obvious footguns. We should also improve the error
message when `@mut` is erroneously reborrowed.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libstd/bitv.rs b/src/libstd/bitv.rs
index 9cf2d145eac..430a5eab64e 100644
--- a/src/libstd/bitv.rs
+++ b/src/libstd/bitv.rs
@@ -700,8 +700,8 @@ impl cmp::Eq for BitvSet {
 }
 
 impl Container for BitvSet {
-    pure fn len(&self) -> uint { self.size }
-    pure fn is_empty(&self) -> bool { self.size == 0 }
+    pure fn len(&const self) -> uint { self.size }
+    pure fn is_empty(&const self) -> bool { self.size == 0 }
 }
 
 impl Mutable for BitvSet {