Auto merge of #31710 - eddyb:reify, r=nikomatsakis

Distinguish fn item types to allow reification from nothing to fn pointers.

The first commit is a rebase of #26284, except for files that have moved since.

This is a [breaking-change], due to:
* each FFI function has a distinct type, like all other functions currently do
* all generic parameters on functions are recorded in their item types, e.g.:
`size_of::<u8>` & `size_of::<i8>`'s types differ despite their identical signature.
* function items are zero-sized, which will stop transmutes from working on them

The first two cases are handled in most cases with the new coerce-unify logic,
which will combine incompatible function item types into function pointers,
at the outer-most level of if-else chains, match arms and array literals.

The last case is specially handled during type-checking such that transmutes
from a function item type to a pointer or integer type will continue to work for
another release cycle, but are being linted against. To get rid of warnings and
ensure your code will continue to compile, cast to a pointer before transmuting.

src/librustc/lint/builtin.rs

@@ -148,6 +148,12 @@ declare_lint! {
     "uses of #[derive] with raw pointers are rarely correct"
 }
 
+declare_lint! {
+    pub TRANSMUTE_FROM_FN_ITEM_TYPES,
+    Warn,
+    "transmute from function item type to pointer-sized type erroneously allowed"
+}
+
 /// Does nothing as a lint pass, but registers some `Lint`s
 /// which are used by other parts of the compiler.
 #[derive(Copy, Clone)]
@@ -177,7 +183,8 @@ impl LintPass for HardwiredLints {
             INVALID_TYPE_PARAM_DEFAULT,
             MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
             CONST_ERR,
-            RAW_POINTER_DERIVE
+            RAW_POINTER_DERIVE,
+            TRANSMUTE_FROM_FN_ITEM_TYPES
         )
     }
 }

src/librustc/lint/context.rs

@@ -1287,6 +1287,9 @@ pub fn check_crate(tcx: &TyCtxt, access_levels: &AccessLevels) {
     }
 
     *tcx.node_lint_levels.borrow_mut() = cx.node_levels.into_inner();
+
+    // Put the lint store back in the session.
+    mem::replace(&mut *tcx.sess.lint_store.borrow_mut(), cx.lints);
 }
 
 pub fn check_ast_crate(sess: &Session, krate: &ast::Crate) {

src/librustc/middle/effect.rs

@@ -44,7 +44,8 @@ enum RootUnsafeContext {
 
 fn type_is_unsafe_function(ty: Ty) -> bool {
     match ty.sty {
-        ty::TyBareFn(_, ref f) => f.unsafety == hir::Unsafety::Unsafe,
+        ty::TyFnDef(_, _, ref f) |
+        ty::TyFnPtr(ref f) => f.unsafety == hir::Unsafety::Unsafe,
         _ => false,
     }
 }

src/librustc/middle/expr_use_visitor.rs

@@ -556,7 +556,7 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
                callee, callee_ty);
         let call_scope = self.tcx().region_maps.node_extent(call.id);
         match callee_ty.sty {
-            ty::TyBareFn(..) => {
+            ty::TyFnDef(..) | ty::TyFnPtr(_) => {
                 self.consume_expr(callee);
             }
             ty::TyError => { }

src/librustc/middle/infer/freshen.rs

@@ -161,7 +161,8 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             ty::TySlice(..) |
             ty::TyRawPtr(..) |
             ty::TyRef(..) |
-            ty::TyBareFn(..) |
+            ty::TyFnDef(..) |
+            ty::TyFnPtr(_) |
             ty::TyTrait(..) |
             ty::TyStruct(..) |
             ty::TyClosure(..) |

src/librustc/middle/infer/mod.rs

@@ -454,7 +454,7 @@ pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
                          -> UnitResult<'tcx>
 {
     debug!("mk_eqty({:?} <: {:?})", a, b);
-    cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
+    cx.eq_types(a_is_expected, origin, a, b)
 }
 
 pub fn mk_eq_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
@@ -466,7 +466,7 @@ pub fn mk_eq_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
 {
     debug!("mk_eq_trait_refs({:?} <: {:?})",
            a, b);
-    cx.commit_if_ok(|_| cx.eq_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
+    cx.eq_trait_refs(a_is_expected, origin, a, b)
 }
 
 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
@@ -478,7 +478,7 @@ pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
 {
     debug!("mk_sub_poly_trait_refs({:?} <: {:?})",
            a, b);
-    cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
+    cx.sub_poly_trait_refs(a_is_expected, origin, a, b)
 }
 
 fn expected_found<T>(a_is_expected: bool,
@@ -1351,18 +1351,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     }
 
     pub fn report_mismatched_types(&self,
-                                   span: Span,
+                                   origin: TypeOrigin,
                                    expected: Ty<'tcx>,
                                    actual: Ty<'tcx>,
-                                   err: &TypeError<'tcx>) {
+                                   err: TypeError<'tcx>) {
         let trace = TypeTrace {
-            origin: TypeOrigin::Misc(span),
+            origin: origin,
             values: Types(ExpectedFound {
                 expected: expected,
                 found: actual
             })
         };
-        self.report_and_explain_type_error(trace, err);
+        self.report_and_explain_type_error(trace, &err);
     }
 
     pub fn report_conflicting_default_types(&self,

src/librustc/middle/intrinsicck.rs

@@ -12,7 +12,7 @@ use dep_graph::DepNode;
 use middle::def::Def;
 use middle::def_id::DefId;
 use middle::subst::{Subst, Substs, EnumeratedItems};
-use middle::ty::{TransmuteRestriction, TyCtxt, TyBareFn};
+use middle::ty::{TransmuteRestriction, TyCtxt};
 use middle::ty::{self, Ty, TypeFoldable};
 
 use std::fmt;
@@ -53,7 +53,7 @@ struct IntrinsicCheckingVisitor<'a, 'tcx: 'a> {
 impl<'a, 'tcx> IntrinsicCheckingVisitor<'a, 'tcx> {
     fn def_id_is_transmute(&self, def_id: DefId) -> bool {
         let intrinsic = match self.tcx.lookup_item_type(def_id).ty.sty {
-            ty::TyBareFn(_, ref bfty) => bfty.abi == RustIntrinsic,
+            ty::TyFnDef(_, _, ref bfty) => bfty.abi == RustIntrinsic,
             _ => return false
         };
         intrinsic && self.tcx.item_name(def_id).as_str() == "transmute"
@@ -238,7 +238,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for IntrinsicCheckingVisitor<'a, 'tcx> {
                 Def::Fn(did) if self.def_id_is_transmute(did) => {
                     let typ = self.tcx.node_id_to_type(expr.id);
                     match typ.sty {
-                        TyBareFn(_, ref bare_fn_ty) if bare_fn_ty.abi == RustIntrinsic => {
+                        ty::TyFnDef(_, _, ref bare_fn_ty) if bare_fn_ty.abi == RustIntrinsic => {
                             if let ty::FnConverging(to) = bare_fn_ty.sig.0.output {
                                 let from = bare_fn_ty.sig.0.inputs[0];
                                 self.check_transmute(expr.span, from, to, expr.id);

src/librustc/middle/subst.rs

@@ -148,11 +148,11 @@ impl<'tcx> Substs<'tcx> {
         Substs { types: types, regions: regions }
     }
 
-    pub fn with_method_from(self,
+    pub fn with_method_from(&self,
                             meth_substs: &Substs<'tcx>)
                             -> Substs<'tcx>
     {
-        let Substs { types, regions } = self;
+        let Substs { types, regions } = self.clone();
         let types = types.with_slice(FnSpace, meth_substs.types.get_slice(FnSpace));
         let regions = regions.map(|r| {
             r.with_slice(FnSpace, meth_substs.regions().get_slice(FnSpace))

src/librustc/middle/traits/coherence.rs

@@ -301,7 +301,8 @@ fn ty_is_local_constructor<'tcx>(tcx: &TyCtxt<'tcx>,
         ty::TyUint(..) |
         ty::TyFloat(..) |
         ty::TyStr |
-        ty::TyBareFn(..) |
+        ty::TyFnDef(..) |
+        ty::TyFnPtr(_) |
         ty::TyArray(..) |
         ty::TySlice(..) |
         ty::TyRawPtr(..) |

src/librustc/middle/traits/mod.rs

@@ -278,7 +278,7 @@ pub enum Vtable<'tcx, N> {
 #[derive(Clone, PartialEq, Eq)]
 pub struct VtableImplData<'tcx, N> {
     pub impl_def_id: DefId,
-    pub substs: subst::Substs<'tcx>,
+    pub substs: &'tcx subst::Substs<'tcx>,
     pub nested: Vec<N>
 }
 

src/librustc/middle/traits/project.rs

@@ -948,7 +948,7 @@ fn confirm_impl_candidate<'cx,'tcx>(
     for impl_item in &selcx.tcx().impl_items.borrow()[&impl_vtable.impl_def_id] {
         if let ty::TypeTraitItem(ref assoc_ty) = impl_or_trait_items_map[&impl_item.def_id()] {
             if assoc_ty.name == obligation.predicate.item_name {
-                return (assoc_ty.ty.unwrap().subst(selcx.tcx(), &impl_vtable.substs),
+                return (assoc_ty.ty.unwrap().subst(selcx.tcx(), impl_vtable.substs),
                         impl_vtable.nested);
             }
         }

src/librustc/middle/traits/select.rs

@@ -1286,7 +1286,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             // provide an impl, but only for suitable `fn` pointers
-            ty::TyBareFn(_, &ty::BareFnTy {
+            ty::TyFnDef(_, _, &ty::BareFnTy {
+                unsafety: hir::Unsafety::Normal,
+                abi: Abi::Rust,
+                sig: ty::Binder(ty::FnSig {
+                    inputs: _,
+                    output: ty::FnConverging(_),
+                    variadic: false
+                })
+            }) |
+            ty::TyFnPtr(&ty::BareFnTy {
                 unsafety: hir::Unsafety::Normal,
                 abi: Abi::Rust,
                 sig: ty::Binder(ty::FnSig {
@@ -1646,7 +1655,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::TyInt(_) |
             ty::TyBool |
             ty::TyFloat(_) |
-            ty::TyBareFn(..) |
+            ty::TyFnDef(..) |
+            ty::TyFnPtr(_) |
             ty::TyChar => {
                 // safe for everything
                 ok_if(Vec::new())
@@ -1850,7 +1860,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::TyInt(_) |
             ty::TyBool |
             ty::TyFloat(_) |
-            ty::TyBareFn(..) |
+            ty::TyFnDef(..) |
+            ty::TyFnPtr(_) |
             ty::TyStr |
             ty::TyError |
             ty::TyInfer(ty::IntVar(_)) |
@@ -2294,7 +2305,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         impl_obligations.append(&mut substs.obligations);
 
         VtableImplData { impl_def_id: impl_def_id,
-                         substs: substs.value,
+                         substs: self.tcx().mk_substs(substs.value),
                          nested: impl_obligations }
     }
 

src/librustc/middle/traits/structural_impls.rs

@@ -147,9 +147,10 @@ impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableImplData<'tcx, N> {
     fn super_fold_with<F:TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        let substs = self.substs.fold_with(folder);
         traits::VtableImplData {
             impl_def_id: self.impl_def_id,
-            substs: self.substs.fold_with(folder),
+            substs: folder.tcx().mk_substs(substs),
             nested: self.nested.fold_with(folder),
         }
     }

src/librustc/middle/ty/adjustment.rs

@@ -155,8 +155,8 @@ impl<'tcx> ty::TyS<'tcx> {
                 match *adjustment {
                     AdjustReifyFnPointer => {
                         match self.sty {
-                            ty::TyBareFn(Some(_), b) => {
-                                cx.mk_fn(None, b)
+                            ty::TyFnDef(_, _, b) => {
+                                cx.mk_ty(ty::TyFnPtr(b))
                             }
                             _ => {
                                 cx.sess.bug(
@@ -168,7 +168,7 @@ impl<'tcx> ty::TyS<'tcx> {
 
                     AdjustUnsafeFnPointer => {
                         match self.sty {
-                            ty::TyBareFn(None, b) => cx.safe_to_unsafe_fn_ty(b),
+                            ty::TyFnPtr(b) => cx.safe_to_unsafe_fn_ty(b),
                             ref b => {
                                 cx.sess.bug(
                                     &format!("AdjustUnsafeFnPointer adjustment on non-fn-ptr: \

src/librustc/middle/ty/cast.rs

@@ -69,7 +69,7 @@ impl<'tcx> CastTy<'tcx> {
                 Some(CastTy::Int(IntTy::CEnum)),
             ty::TyRawPtr(ref mt) => Some(CastTy::Ptr(mt)),
             ty::TyRef(_, ref mt) => Some(CastTy::RPtr(mt)),
-            ty::TyBareFn(..) => Some(CastTy::FnPtr),
+            ty::TyFnPtr(..) => Some(CastTy::FnPtr),
             _ => None,
         }
     }

src/librustc/middle/ty/contents.rs

@@ -187,7 +187,7 @@ impl<'tcx> ty::TyS<'tcx> {
                 // Scalar and unique types are sendable, and durable
                 ty::TyInfer(ty::FreshIntTy(_)) | ty::TyInfer(ty::FreshFloatTy(_)) |
                 ty::TyBool | ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) |
-                ty::TyBareFn(..) | ty::TyChar => {
+                ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyChar => {
                     TC::None
                 }
 

src/librustc/middle/ty/context.rs

@@ -41,7 +41,6 @@ use std::borrow::Borrow;
 use std::cell::{Cell, RefCell, Ref};
 use std::hash::{Hash, Hasher};
 use std::rc::Rc;
-use syntax::abi::Abi;
 use syntax::ast::{self, Name, NodeId};
 use syntax::attr;
 use syntax::parse::token::special_idents;
@@ -734,8 +733,8 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn print_debug_stats(&self) {
         sty_debug_print!(
             self,
-            TyEnum, TyBox, TyArray, TySlice, TyRawPtr, TyRef, TyBareFn, TyTrait,
-            TyStruct, TyClosure, TyTuple, TyParam, TyInfer, TyProjection);
+            TyEnum, TyBox, TyArray, TySlice, TyRawPtr, TyRef, TyFnDef, TyFnPtr,
+            TyTrait, TyStruct, TyClosure, TyTuple, TyParam, TyInfer, TyProjection);
 
         println!("Substs interner: #{}", self.substs_interner.borrow().len());
         println!("BareFnTy interner: #{}", self.bare_fn_interner.borrow().len());
@@ -792,12 +791,11 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Create an unsafe fn ty based on a safe fn ty.
     pub fn safe_to_unsafe_fn_ty(&self, bare_fn: &BareFnTy<'tcx>) -> Ty<'tcx> {
         assert_eq!(bare_fn.unsafety, hir::Unsafety::Normal);
-        let unsafe_fn_ty_a = self.mk_bare_fn(ty::BareFnTy {
+        self.mk_fn_ptr(ty::BareFnTy {
             unsafety: hir::Unsafety::Unsafe,
             abi: bare_fn.abi,
             sig: bare_fn.sig.clone()
-        });
-        self.mk_fn(None, unsafe_fn_ty_a)
+        })
     }
 
     pub fn mk_bare_fn(&self, bare_fn: BareFnTy<'tcx>) -> &'tcx BareFnTy<'tcx> {
@@ -946,26 +944,14 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_ty(TyBool)
     }
 
-    pub fn mk_fn(&self,
-                 opt_def_id: Option<DefId>,
-                 fty: &'tcx BareFnTy<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(TyBareFn(opt_def_id, fty))
-    }
-
-    pub fn mk_ctor_fn(&self,
-                      def_id: DefId,
-                      input_tys: &[Ty<'tcx>],
-                      output: Ty<'tcx>) -> Ty<'tcx> {
-        let input_args = input_tys.iter().cloned().collect();
-        self.mk_fn(Some(def_id), self.mk_bare_fn(BareFnTy {
-            unsafety: hir::Unsafety::Normal,
-            abi: Abi::Rust,
-            sig: ty::Binder(ty::FnSig {
-                inputs: input_args,
-                output: ty::FnConverging(output),
-                variadic: false
-            })
-        }))
+    pub fn mk_fn_def(&self, def_id: DefId,
+                     substs: &'tcx Substs<'tcx>,
+                     fty: BareFnTy<'tcx>) -> Ty<'tcx> {
+        self.mk_ty(TyFnDef(def_id, substs, self.mk_bare_fn(fty)))
+    }
+
+    pub fn mk_fn_ptr(&self, fty: BareFnTy<'tcx>) -> Ty<'tcx> {
+        self.mk_ty(TyFnPtr(self.mk_bare_fn(fty)))
     }
 
     pub fn mk_trait(&self,

src/librustc/middle/ty/error.rs

@@ -223,8 +223,8 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::TySlice(_) => "slice".to_string(),
             ty::TyRawPtr(_) => "*-ptr".to_string(),
             ty::TyRef(_, _) => "&-ptr".to_string(),
-            ty::TyBareFn(Some(_), _) => format!("fn item"),
-            ty::TyBareFn(None, _) => "fn pointer".to_string(),
+            ty::TyFnDef(..) => format!("fn item"),
+            ty::TyFnPtr(_) => "fn pointer".to_string(),
             ty::TyTrait(ref inner) => {
                 format!("trait {}", cx.item_path_str(inner.principal_def_id()))
             }

src/librustc/middle/ty/fast_reject.rs

@@ -83,7 +83,7 @@ pub fn simplify_type(tcx: &TyCtxt,
         ty::TyTuple(ref tys) => {
             Some(TupleSimplifiedType(tys.len()))
         }
-        ty::TyBareFn(_, ref f) => {
+        ty::TyFnDef(_, _, ref f) | ty::TyFnPtr(ref f) => {
             Some(FunctionSimplifiedType(f.sig.0.inputs.len()))
         }
         ty::TyProjection(_) | ty::TyParam(_) => {

src/librustc/middle/ty/flags.rs

@@ -134,7 +134,12 @@ impl FlagComputation {
                 self.add_tys(&ts[..]);
             }
 
-            &ty::TyBareFn(_, ref f) => {
+            &ty::TyFnDef(_, substs, ref f) => {
+                self.add_substs(substs);
+                self.add_fn_sig(&f.sig);
+            }
+
+            &ty::TyFnPtr(ref f) => {
                 self.add_fn_sig(&f.sig);
             }
         }

src/librustc/middle/ty/outlives.rs

@@ -182,7 +182,8 @@ fn compute_components<'a,'tcx>(infcx: &InferCtxt<'a,'tcx>,
         ty::TyRawPtr(..) |      // ...
         ty::TyRef(..) |         // OutlivesReference
         ty::TyTuple(..) |       // ...
-        ty::TyBareFn(..) |      // OutlivesFunction (*)
+        ty::TyFnDef(..) |       // OutlivesFunction (*)
+        ty::TyFnPtr(_) |        // OutlivesFunction (*)
         ty::TyTrait(..) |       // OutlivesObject, OutlivesFragment (*)
         ty::TyError => {
             // (*) Bare functions and traits are both binders. In the