allow for loop bodies

src/rustc/middle/borrowck.rs

@@ -654,7 +654,7 @@ fn check_pure_callee_or_arg(pc: purity_cause, expr: @ast::expr) {
                 self.fn_args.contains(did.node);
             if is_fn_arg { ret; } // case (a) above
           }
-          ast::expr_fn_block(*) | ast::expr_fn(*) {
+          ast::expr_fn_block(*) | ast::expr_fn(*) | ast::expr_loop_body(*) {
             if self.is_stack_closure(expr.id) { ret; } // case (b) above
           }
           _ {}

src/test/compile-fail/pure-loop-body.rs

@@ -0,0 +1,21 @@
+pure fn range(from: uint, to: uint, f: fn(uint) -> bool) {
+    let mut i = from;
+    while i < to {
+        if !f(i) {ret;} // Note: legal to call argument, even if it is not pure.
+        i += 1u;
+    }
+}
+
+pure fn range2(from: uint, to: uint, f: fn(uint)) {
+    for range(from, to) { |i|
+        f(i*2u);
+    }
+}
+
+pure fn range3(from: uint, to: uint, f: {x: fn(uint)}) {
+    for range(from, to) { |i|
+        f.x(i*2u); //! ERROR access to impure function prohibited
+    }
+}
+
+fn main() {}