Auto merge of #57898 - Centril:rollup, r=Centril

Rollup of 5 pull requests

Successful merges:

 - #56233 (Miri and miri-related code contains repetitions of `(n << amt) >> amt`)
 - #57645 (distinguish "no data" from "heterogeneous" in ABI)
 - #57734 (Fix evaluating trivial drop glue in constants)
 - #57886 (Add suggestion for moving type declaration before associated type bindings in generic arguments.)
 - #57890 (Fix wording in diagnostics page)

Failed merges:

r? @ghost

src/librustc/ty/mod.rs

@@ -2937,16 +2937,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    /// Given the DefId of an item, returns its MIR, borrowed immutably.
-    /// Returns None if there is no MIR for the DefId
-    pub fn maybe_optimized_mir(self, did: DefId) -> Option<&'gcx Mir<'gcx>> {
-        if self.is_mir_available(did) {
-            Some(self.optimized_mir(did))
-        } else {
-            None
-        }
-    }
-
     /// Get the attributes of a definition.
     pub fn get_attrs(self, did: DefId) -> Attributes<'gcx> {
         if let Some(id) = self.hir().as_local_node_id(did) {

src/librustc_driver/driver.rs

@@ -22,7 +22,7 @@ use rustc_incremental;
 use rustc_metadata::creader::CrateLoader;
 use rustc_metadata::cstore::{self, CStore};
 use rustc_mir as mir;
-use rustc_passes::{self, ast_validation, hir_stats, loops, rvalue_promotion};
+use rustc_passes::{self, ast_validation, hir_stats, loops, rvalue_promotion, layout_test};
 use rustc_plugin as plugin;
 use rustc_plugin::registry::Registry;
 use rustc_privacy;
@@ -1287,6 +1287,9 @@ where
                     mir::transform::check_unsafety::check_unsafety(tcx, def_id)
                 }
             });
+
+            time(sess, "layout testing", || layout_test::test_layout(tcx));
+
             // Avoid overwhelming user with errors if type checking failed.
             // I'm not sure how helpful this is, to be honest, but it avoids
             // a

src/librustc_lint/types.rs

@@ -21,6 +21,8 @@ use syntax::source_map;
 
 use rustc::hir;
 
+use rustc::mir::interpret::{sign_extend, truncate};
+
 declare_lint! {
     UNUSED_COMPARISONS,
     Warn,
@@ -368,14 +370,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
             let (t, actually) = match ty {
                 ty::Int(t) => {
                     let ity = attr::IntType::SignedInt(t);
-                    let bits = layout::Integer::from_attr(&cx.tcx, ity).size().bits();
-                    let actually = (val << (128 - bits)) as i128 >> (128 - bits);
+                    let size = layout::Integer::from_attr(&cx.tcx, ity).size();
+                    let actually = sign_extend(val, size) as i128;
                     (format!("{:?}", t), actually.to_string())
                 }
                 ty::Uint(t) => {
                     let ity = attr::IntType::UnsignedInt(t);
-                    let bits = layout::Integer::from_attr(&cx.tcx, ity).size().bits();
-                    let actually = (val << (128 - bits)) >> (128 - bits);
+                    let size = layout::Integer::from_attr(&cx.tcx, ity).size();
+                    let actually = truncate(val, size);
                     (format!("{:?}", t), actually.to_string())
                 }
                 _ => bug!(),

src/librustc_mir/const_eval.rs

@@ -340,19 +340,22 @@ impl<'a, 'mir, 'tcx> interpret::Machine<'a, 'mir, 'tcx>
         ret: Option<mir::BasicBlock>,
     ) -> EvalResult<'tcx, Option<&'mir mir::Mir<'tcx>>> {
         debug!("eval_fn_call: {:?}", instance);
-        // Execution might have wandered off into other crates, so we cannot to a stability-
-        // sensitive check here.  But we can at least rule out functions that are not const
-        // at all.
-        if !ecx.tcx.is_const_fn_raw(instance.def_id()) {
-            // Some functions we support even if they are non-const -- but avoid testing
-            // that for const fn!  We certainly do *not* want to actually call the fn
-            // though, so be sure we return here.
-            return if ecx.hook_fn(instance, args, dest)? {
-                ecx.goto_block(ret)?; // fully evaluated and done
-                Ok(None)
-            } else {
-                err!(MachineError(format!("calling non-const function `{}`", instance)))
-            };
+        // Only check non-glue functions
+        if let ty::InstanceDef::Item(def_id) = instance.def {
+            // Execution might have wandered off into other crates, so we cannot to a stability-
+            // sensitive check here.  But we can at least rule out functions that are not const
+            // at all.
+            if !ecx.tcx.is_const_fn_raw(def_id) {
+                // Some functions we support even if they are non-const -- but avoid testing
+                // that for const fn!  We certainly do *not* want to actually call the fn
+                // though, so be sure we return here.
+                return if ecx.hook_fn(instance, args, dest)? {
+                    ecx.goto_block(ret)?; // fully evaluated and done
+                    Ok(None)
+                } else {
+                    err!(MachineError(format!("calling non-const function `{}`", instance)))
+                };
+            }
         }
         // This is a const fn. Call it.
         Ok(Some(match ecx.load_mir(instance.def) {

src/librustc_mir/interpret/eval_context.rs

@@ -273,11 +273,11 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tc
         }
         trace!("load mir {:?}", instance);
         match instance {
-            ty::InstanceDef::Item(def_id) => {
-                self.tcx.maybe_optimized_mir(def_id).ok_or_else(||
-                    EvalErrorKind::NoMirFor(self.tcx.item_path_str(def_id)).into()
-                )
-            }
+            ty::InstanceDef::Item(def_id) => if self.tcx.is_mir_available(did) {
+                Ok(self.tcx.optimized_mir(did))
+            } else {
+                err!(NoMirFor(self.tcx.item_path_str(def_id)))
+            },
             _ => Ok(self.tcx.instance_mir(instance)),
         }
     }

src/librustc_passes/layout_test.rs

@@ -0,0 +1,132 @@
+use rustc::hir;
+use rustc::hir::def_id::DefId;
+use rustc::hir::itemlikevisit::ItemLikeVisitor;
+use rustc::hir::ItemKind;
+use rustc::ty::layout::HasDataLayout;
+use rustc::ty::layout::HasTyCtxt;
+use rustc::ty::layout::LayoutOf;
+use rustc::ty::layout::TargetDataLayout;
+use rustc::ty::layout::TyLayout;
+use rustc::ty::ParamEnv;
+use rustc::ty::Ty;
+use rustc::ty::TyCtxt;
+use syntax::ast::Attribute;
+
+pub fn test_layout<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
+    if tcx.features().rustc_attrs {
+        // if the `rustc_attrs` feature is not enabled, don't bother testing layout
+        tcx.hir()
+            .krate()
+            .visit_all_item_likes(&mut VarianceTest { tcx });
+    }
+}
+
+struct VarianceTest<'a, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+}
+
+impl<'a, 'tcx> ItemLikeVisitor<'tcx> for VarianceTest<'a, 'tcx> {
+    fn visit_item(&mut self, item: &'tcx hir::Item) {
+        let item_def_id = self.tcx.hir().local_def_id(item.id);
+
+        if let ItemKind::Ty(..) = item.node {
+            for attr in self.tcx.get_attrs(item_def_id).iter() {
+                if attr.check_name("rustc_layout") {
+                    self.dump_layout_of(item_def_id, item, attr);
+                }
+            }
+        }
+    }
+
+    fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) {}
+    fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) {}
+}
+
+impl<'a, 'tcx> VarianceTest<'a, 'tcx> {
+    fn dump_layout_of(&self, item_def_id: DefId, item: &hir::Item, attr: &Attribute) {
+        let tcx = self.tcx;
+        let param_env = self.tcx.param_env(item_def_id);
+        let ty = self.tcx.type_of(item_def_id);
+        match self.tcx.layout_of(param_env.and(ty)) {
+            Ok(ty_layout) => {
+                // Check out the `#[rustc_layout(..)]` attribute to tell what to dump.
+                // The `..` are the names of fields to dump.
+                let meta_items = attr.meta_item_list().unwrap_or_default();
+                for meta_item in meta_items {
+                    let name = meta_item.word().map(|mi| mi.name().as_str());
+                    let name = name.as_ref().map(|s| &s[..]).unwrap_or("");
+
+                    match name {
+                        "abi" => {
+                            self.tcx
+                                .sess
+                                .span_err(item.span, &format!("abi: {:?}", ty_layout.abi));
+                        }
+
+                        "align" => {
+                            self.tcx
+                                .sess
+                                .span_err(item.span, &format!("align: {:?}", ty_layout.align));
+                        }
+
+                        "size" => {
+                            self.tcx
+                                .sess
+                                .span_err(item.span, &format!("size: {:?}", ty_layout.size));
+                        }
+
+                        "homogeneous_aggregate" => {
+                            self.tcx.sess.span_err(
+                                item.span,
+                                &format!(
+                                    "homogeneous_aggregate: {:?}",
+                                    ty_layout
+                                        .homogeneous_aggregate(&UnwrapLayoutCx { tcx, param_env }),
+                                ),
+                            );
+                        }
+
+                        _ => {
+                            self.tcx.sess.span_err(
+                                meta_item.span,
+                                &format!("unrecognized field name `{}`", name),
+                            );
+                        }
+                    }
+                }
+            }
+
+            Err(layout_error) => {
+                self.tcx
+                    .sess
+                    .span_err(item.span, &format!("layout error: {:?}", layout_error));
+            }
+        }
+    }
+}
+
+struct UnwrapLayoutCx<'me, 'tcx> {
+    tcx: TyCtxt<'me, 'tcx, 'tcx>,
+    param_env: ParamEnv<'tcx>,
+}
+
+impl<'me, 'tcx> LayoutOf for UnwrapLayoutCx<'me, 'tcx> {
+    type Ty = Ty<'tcx>;
+    type TyLayout = TyLayout<'tcx>;
+
+    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
+        self.tcx.layout_of(self.param_env.and(ty)).unwrap()
+    }
+}
+
+impl<'me, 'tcx> HasTyCtxt<'tcx> for UnwrapLayoutCx<'me, 'tcx> {
+    fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
+        self.tcx
+    }
+}
+
+impl<'me, 'tcx> HasDataLayout for UnwrapLayoutCx<'me, 'tcx> {
+    fn data_layout(&self) -> &TargetDataLayout {
+        self.tcx.data_layout()
+    }
+}

src/librustc_passes/lib.rs

@@ -32,6 +32,7 @@ mod diagnostics;
 pub mod ast_validation;
 pub mod rvalue_promotion;
 pub mod hir_stats;
+pub mod layout_test;
 pub mod loops;
 
 __build_diagnostic_array! { librustc_passes, DIAGNOSTICS }

src/librustc_target/abi/call/aarch64.rs

@@ -6,7 +6,7 @@ fn is_homogeneous_aggregate<'a, Ty, C>(cx: &C, arg: &mut ArgType<'a, Ty>)
     where Ty: TyLayoutMethods<'a, C> + Copy,
           C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
 {
-    arg.layout.homogeneous_aggregate(cx).and_then(|unit| {
+    arg.layout.homogeneous_aggregate(cx).unit().and_then(|unit| {
         let size = arg.layout.size;
 
         // Ensure we have at most four uniquely addressable members.

src/librustc_target/abi/call/arm.rs

@@ -7,7 +7,7 @@ fn is_homogeneous_aggregate<'a, Ty, C>(cx: &C, arg: &mut ArgType<'a, Ty>)
     where Ty: TyLayoutMethods<'a, C> + Copy,
           C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
 {
-    arg.layout.homogeneous_aggregate(cx).and_then(|unit| {
+    arg.layout.homogeneous_aggregate(cx).unit().and_then(|unit| {
         let size = arg.layout.size;
 
         // Ensure we have at most four uniquely addressable members.

src/librustc_target/abi/call/asmjs.rs

@@ -11,7 +11,7 @@ fn classify_ret_ty<'a, Ty, C>(cx: &C, ret: &mut ArgType<'a, Ty>)
           C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
 {
     if ret.layout.is_aggregate() {
-        if let Some(unit) = ret.layout.homogeneous_aggregate(cx) {
+        if let Some(unit) = ret.layout.homogeneous_aggregate(cx).unit() {
             let size = ret.layout.size;
             if unit.size == size {
                 ret.cast_to(Uniform {