From 81533ff737f2d71c7518188b71fbafd73e0d1434 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Tue, 11 Oct 2011 17:31:23 -0700
Subject: [PATCH] add pass to check that unsafe fns cannot be used as values

---
 src/comp/driver/rustc.rs                      |  4 +-
 src/comp/middle/unsafeck.rs                   | 72 +++++++++++++++++++
 src/comp/rustc.rc                             |  1 +
 .../compile-fail/unsafe-fn-used-as-value.rs   |  9 +++
 4 files changed, 85 insertions(+), 1 deletion(-)
 create mode 100644 src/comp/middle/unsafeck.rs
 create mode 100644 src/test/compile-fail/unsafe-fn-used-as-value.rs

diff --git a/src/comp/driver/rustc.rs b/src/comp/driver/rustc.rs
index 76819b996054..84409978bda3 100644
--- a/src/comp/driver/rustc.rs
+++ b/src/comp/driver/rustc.rs
@@ -5,7 +5,7 @@ import metadata::{creader, cstore};
 import syntax::parse::{parser, token};
 import syntax::{ast, codemap};
 import front::attr;
-import middle::{trans, resolve, freevars, kind, ty, typeck};
+import middle::{trans, resolve, freevars, kind, ty, typeck, unsafeck};
 import middle::tstate::ck;
 import syntax::print::{pp, pprust};
 import util::{ppaux, common, filesearch};
@@ -129,6 +129,8 @@ fn compile_input(sess: session::session, cfg: ast::crate_cfg, input: str,
              bind freevars::annotate_freevars(def_map, crate));
     let ty_cx = ty::mk_ctxt(sess, def_map, ext_map, ast_map, freevars);
     time(time_passes, "typechecking", bind typeck::check_crate(ty_cx, crate));
+    time(time_passes, "unsafechecking",
+         bind unsafeck::unsafeck_crate(ty_cx, crate));
     time(time_passes, "alt checking",
          bind middle::check_alt::check_crate(ty_cx, crate));
     if sess.get_opts().run_typestate {
diff --git a/src/comp/middle/unsafeck.rs b/src/comp/middle/unsafeck.rs
new file mode 100644
index 000000000000..251258f11a8b
--- /dev/null
+++ b/src/comp/middle/unsafeck.rs
@@ -0,0 +1,72 @@
+import syntax::ast;
+import syntax::visit;
+import std::option::some;
+import syntax::print::pprust::{expr_to_str, path_to_str};
+
+export unsafeck_crate;
+
+type unsafe_ctx = {
+    tcx: ty::ctxt,
+    unsafe_fn_legal: bool
+};
+
+fn unsafeck_view_item(_vi: @ast::view_item,
+                      _ctx: unsafe_ctx,
+                      _v: visit::vt<unsafe_ctx>) {
+    // Ignore paths that appear in use, import, etc
+}
+
+fn unsafeck_expr(expr: @ast::expr,
+                 ctx: unsafe_ctx,
+                 v: visit::vt<unsafe_ctx>) {
+    alt expr.node {
+      ast::expr_path(path) {
+        if !ctx.unsafe_fn_legal {
+            alt ctx.tcx.def_map.find(expr.id) {
+              some(ast::def_fn(_, ast::unsafe_fn.)) |
+              some(ast::def_native_fn(_, ast::unsafe_fn.)) {
+                log_err ("expr=", expr_to_str(expr));
+                ctx.tcx.sess.span_fatal(
+                    expr.span,
+                    "unsafe functions can only be called");
+              }
+
+              _ {}
+            }
+        }
+      }
+
+      ast::expr_call(f, args) {
+        let f_ctx = {unsafe_fn_legal: true with ctx};
+        visit::visit_expr(f, f_ctx, v);
+
+        let args_ctx = {unsafe_fn_legal: false with ctx};
+        visit::visit_exprs(args, args_ctx, v);
+      }
+
+      _ {
+        let subctx = {unsafe_fn_legal: false with ctx};
+        visit::visit_expr(expr, subctx, v);
+      }
+    }
+}
+
+fn unsafeck_crate(tcx: ty::ctxt, crate: @ast::crate) {
+    let visit =
+        visit::mk_vt(
+            @{visit_expr: unsafeck_expr,
+              visit_view_item: unsafeck_view_item
+                  with *visit::default_visitor()});
+    let ctx = {tcx: tcx, unsafe_fn_legal: false};
+    visit::visit_crate(*crate, ctx, visit);
+}
+
+
+// Local Variables:
+// mode: rust
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End:
diff --git a/src/comp/rustc.rc b/src/comp/rustc.rc
index 9b1dff757699..2f861155e1ca 100644
--- a/src/comp/rustc.rc
+++ b/src/comp/rustc.rc
@@ -25,6 +25,7 @@ mod middle {
     mod ast_map;
     mod resolve;
     mod typeck;
+    mod unsafeck;
     mod check_alt;
     mod mut;
     mod alias;
diff --git a/src/test/compile-fail/unsafe-fn-used-as-value.rs b/src/test/compile-fail/unsafe-fn-used-as-value.rs
new file mode 100644
index 000000000000..e2fa46b0374f
--- /dev/null
+++ b/src/test/compile-fail/unsafe-fn-used-as-value.rs
@@ -0,0 +1,9 @@
+// -*- rust -*-
+// error-pattern: unsafe functions can only be called
+
+unsafe fn f() { ret; }
+
+fn main() {
+    let x = f;
+    x();
+}