make all arguments modes immutable

note: you can still move from copy/move mode args

1 files changed, 30 insertions, 0 deletions

diff --git a/src/test/compile-fail/mutable-arguments.rs b/src/test/compile-fail/mutable-arguments.rs
new file mode 100644
index 00000000000..79e7f412163
--- /dev/null
+++ b/src/test/compile-fail/mutable-arguments.rs
@@ -0,0 +1,30 @@
+// Note: it would be nice to give fewer warnings in these cases.
+
+fn mutate_by_mut_ref(&x: uint) {
+    x = 0u;
+}
+
+fn mutate_by_ref(&&x: uint) {
+    //!^ WARNING unused variable: `x`
+    x = 0u; //! ERROR assigning to argument
+}
+
+fn mutate_by_val(++x: uint) {
+    //!^ WARNING unused variable: `x`
+    x = 0u; //! ERROR assigning to argument
+}
+
+fn mutate_by_copy(+x: uint) {
+    //!^ WARNING unused variable: `x`
+    x = 0u; //! ERROR assigning to argument
+    //!^ WARNING value assigned to `x` is never read
+}
+
+fn mutate_by_move(-x: uint) {
+    //!^ WARNING unused variable: `x`
+    x = 0u; //! ERROR assigning to argument
+    //!^ WARNING value assigned to `x` is never read
+}
+
+fn main() {
+}