Make to_str pure and fix const parameters for str-mutating functions

Two separate changes that got intertwined (sorry):

Make to_str pure. Closes #3691

In str, change functions like push_char to take an &mut str instead of
an &str. Closes #3710

3 files changed, 3 insertions, 3 deletions

diff --git a/src/test/auxiliary/cci_class_cast.rs b/src/test/auxiliary/cci_class_cast.rs
index 288fe66dd20..ca2af387587 100644
--- a/src/test/auxiliary/cci_class_cast.rs
+++ b/src/test/auxiliary/cci_class_cast.rs
@@ -13,7 +13,7 @@ struct cat {
 }
 
     impl cat : ToStr {
-        fn to_str() -> ~str { self.name }
+       pure fn to_str() -> ~str { self.name }
     }
 
     priv impl cat {
diff --git a/src/test/run-pass/class-separate-impl.rs b/src/test/run-pass/class-separate-impl.rs
index c7517ab1b3d..8a51eb33857 100644
--- a/src/test/run-pass/class-separate-impl.rs
+++ b/src/test/run-pass/class-separate-impl.rs
@@ -45,7 +45,7 @@ fn cat(in_x : uint, in_y : int, in_name: ~str) -> cat {
 }
 
 impl cat: ToStr {
-  fn to_str() -> ~str { self.name }
+  pure fn to_str() -> ~str { self.name }
 }
 
 fn print_out<T: ToStr>(thing: T, expected: ~str) {
diff --git a/src/test/run-pass/issue-2904.rs b/src/test/run-pass/issue-2904.rs
index 6d771dc7386..4bb2c561422 100644
--- a/src/test/run-pass/issue-2904.rs
+++ b/src/test/run-pass/issue-2904.rs
@@ -16,7 +16,7 @@ enum square {
 }
 
 impl square: to_str::ToStr {
-    fn to_str() -> ~str {
+    pure fn to_str() -> ~str {
         match self {
           bot => { ~"R" }
           wall => { ~"#" }