Port of pcwalton removal of #[unsafe_destructor] check.

src/librustc_typeck/check/wf.rs

@@ -23,7 +23,6 @@ use util::ppaux::{Repr, UserString};
 use std::collections::HashSet;
 use syntax::ast;
 use syntax::ast_util::local_def;
-use syntax::attr;
 use syntax::codemap::Span;
 use syntax::parse::token::{self, special_idents};
 use syntax::visit;
@@ -250,22 +249,6 @@ impl<'ccx, 'tcx> CheckTypeWellFormedVisitor<'ccx, 'tcx> {
                                                         &fcx.inh.param_env.free_substs,
                                                         &trait_ref);
 
-            // There are special rules that apply to drop.
-            if
-                fcx.tcx().lang_items.drop_trait() == Some(trait_ref.def_id) &&
-                !attr::contains_name(&item.attrs, "unsafe_destructor")
-            {
-                match self_ty.sty {
-                    ty::ty_struct(def_id, _) |
-                    ty::ty_enum(def_id, _) => {
-                        check_struct_safe_for_destructor(fcx, item.span, def_id);
-                    }
-                    _ => {
-                        // Coherence already reports an error in this case.
-                    }
-                }
-            }
-
             if fcx.tcx().lang_items.copy_trait() == Some(trait_ref.def_id) {
                 // This is checked in coherence.
                 return
@@ -761,22 +744,3 @@ fn filter_to_trait_obligations<'tcx>(bounds: ty::InstantiatedPredicates<'tcx>)
     }
     result
 }
-
-///////////////////////////////////////////////////////////////////////////
-// Special drop trait checking
-
-fn check_struct_safe_for_destructor<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
-                                              span: Span,
-                                              struct_did: ast::DefId) {
-    let struct_tpt = ty::lookup_item_type(fcx.tcx(), struct_did);
-    if struct_tpt.generics.has_type_params(subst::TypeSpace)
-        || struct_tpt.generics.has_region_params(subst::TypeSpace)
-    {
-        span_err!(fcx.tcx().sess, span, E0141,
-                  "cannot implement a destructor on a structure \
-                   with type parameters");
-        span_note!(fcx.tcx().sess, span,
-                   "use \"#[unsafe_destructor]\" on the implementation \
-                    to force the compiler to allow this");
-    }
-}

src/libsyntax/feature_gate.rs

@@ -58,7 +58,6 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
     ("log_syntax", "1.0.0", Active),
     ("trace_macros", "1.0.0", Active),
     ("concat_idents", "1.0.0", Active),
-    ("unsafe_destructor", "1.0.0", Active),
     ("intrinsics", "1.0.0", Active),
     ("lang_items", "1.0.0", Active),
 
@@ -92,6 +91,10 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
     ("start", "1.0.0", Active),
     ("main", "1.0.0", Active),
 
+    // Deprecate after snapshot
+    // SNAP a923278
+    ("unsafe_destructor", "1.0.0", Active),
+
     // A temporary feature gate used to enable parser extensions needed
     // to bootstrap fix for #5723.
     ("issue_5723_bootstrap", "1.0.0", Accepted),
@@ -193,7 +196,6 @@ pub const KNOWN_ATTRIBUTES: &'static [(&'static str, AttributeType)] = &[
     ("repr", Normal),
     ("path", Normal),
     ("abi", Normal),
-    ("unsafe_destructor", Normal),
     ("automatically_derived", Normal),
     ("no_mangle", Normal),
     ("no_link", Normal),
@@ -205,7 +207,8 @@ pub const KNOWN_ATTRIBUTES: &'static [(&'static str, AttributeType)] = &[
     ("link_args", Normal),
     ("macro_escape", Normal),
 
-
+    ("unsafe_destructor", Gated("unsafe_destructor",
+                                "`#[unsafe_destructor]` does nothing anymore")),
     ("staged_api", Gated("staged_api",
                          "staged_api is for use by rustc only")),
     ("plugin", Gated("plugin",
@@ -571,15 +574,6 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                     _ => {}
                 }
 
-                if attr::contains_name(&i.attrs,
-                                       "unsafe_destructor") {
-                    self.gate_feature("unsafe_destructor",
-                                      i.span,
-                                      "`#[unsafe_destructor]` allows too \
-                                       many unsafe patterns and may be \
-                                       removed in the future");
-                }
-
                 if attr::contains_name(&i.attrs[..],
                                        "old_orphan_check") {
                     self.gate_feature(

src/test/compile-fail/gated-unsafe-destructor.rs

@@ -10,14 +10,18 @@
 
 // Test that `#[unsafe_destructor]` attribute is gated by `unsafe_destructor`
 // feature gate.
+//
+// (This test can be removed entirely when we remove the
+// `unsafe_destructor` feature itself.)
 
 struct D<'a>(&'a u32);
 
 #[unsafe_destructor]
+//~^ ERROR `#[unsafe_destructor]` does nothing anymore
+//~| HELP: add #![feature(unsafe_destructor)] to the crate attributes to enable
+// (but of couse there is no point in doing so)
 impl<'a> Drop for D<'a> {
-    //~^ ERROR `#[unsafe_destructor]` allows too many unsafe patterns
     fn drop(&mut self) { }
 }
-//~^ HELP: add #![feature(unsafe_destructor)] to the crate attributes to enable
 
 pub fn main() { }