Use more accurate ConstraintCategorys

Adds UseAsConst and UseAsStatic to replace Return in consts/statics.
Don't report the arguments to an overloaded operator as CallArguments.
Also don't report "escaping data" in these items.

Author: matthewjasper

src/librustc/ich/impls_mir.rs

@@ -557,6 +557,8 @@ impl_stable_hash_for!(struct mir::ClosureOutlivesRequirement<'tcx> {
 
 impl_stable_hash_for!(enum mir::ConstraintCategory {
     Return,
+    UseAsConst,
+    UseAsStatic,
     TypeAnnotation,
     Cast,
     ClosureBounds,

src/librustc/mir/mod.rs

@@ -2725,6 +2725,8 @@ pub struct ClosureOutlivesRequirement<'tcx> {
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub enum ConstraintCategory {
     Return,
+    UseAsConst,
+    UseAsStatic,
     TypeAnnotation,
     Cast,
 

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs

@@ -40,6 +40,8 @@ impl ConstraintDescription for ConstraintCategory {
         match self {
             ConstraintCategory::Assignment => "assignment ",
             ConstraintCategory::Return => "returning this value ",
+            ConstraintCategory::UseAsConst => "using this value as a constant ",
+            ConstraintCategory::UseAsStatic => "using this value as a static ",
             ConstraintCategory::Cast => "cast ",
             ConstraintCategory::CallArgument => "argument ",
             ConstraintCategory::TypeAnnotation => "type annotation ",
@@ -375,12 +377,18 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         let outlived_fr_name_and_span =
             self.get_var_name_and_span_for_region(infcx.tcx, mir, outlived_fr);
 
-        let escapes_from = if infcx.tcx.is_closure(mir_def_id) { "closure" } else { "function" };
+        let escapes_from = match self.universal_regions.defining_ty {
+            DefiningTy::Closure(..) => "closure",
+            DefiningTy::Generator(..) => "generator",
+            DefiningTy::FnDef(..) => "function",
+            DefiningTy::Const(..) => "const"
+        };
 
         // Revert to the normal error in these cases.
         // Assignments aren't "escapes" in function items.
         if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none())
             || (category == ConstraintCategory::Assignment && escapes_from == "function")
+            || escapes_from == "const"
         {
             return self.report_general_error(mir, infcx, mir_def_id,
                                              fr, true, outlived_fr, false,

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -23,7 +23,7 @@ use borrow_check::nll::renumber;
 use borrow_check::nll::type_check::free_region_relations::{
     CreateResult, UniversalRegionRelations,
 };
-use borrow_check::nll::universal_regions::UniversalRegions;
+use borrow_check::nll::universal_regions::{DefiningTy, UniversalRegions};
 use borrow_check::nll::ToRegionVid;
 use dataflow::move_paths::MoveData;
 use dataflow::FlowAtLocation;
@@ -1209,7 +1209,21 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 // of lowering. Assignments to other sorts of places *are* interesting
                 // though.
                 let category = match *place {
-                    Place::Local(RETURN_PLACE) => ConstraintCategory::Return,
+                    Place::Local(RETURN_PLACE) => if let Some(BorrowCheckContext {
+                        universal_regions: UniversalRegions {
+                            defining_ty: DefiningTy::Const(def_id, _),
+                            ..
+                        },
+                        ..
+                    }) = self.borrowck_context {
+                        if tcx.is_static(*def_id).is_some() {
+                            ConstraintCategory::UseAsStatic
+                        } else {
+                            ConstraintCategory::UseAsConst
+                        }
+                    } else {
+                        ConstraintCategory::Return
+                    }
                     Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -1391,6 +1405,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 ref func,
                 ref args,
                 ref destination,
+                from_hir_call,
                 ..
             } => {
                 let func_ty = func.ty(mir, tcx);
@@ -1435,7 +1450,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     }
                 }
 
-                self.check_call_inputs(mir, term, &sig, args, term_location);
+                self.check_call_inputs(mir, term, &sig, args, term_location, from_hir_call);
             }
             TerminatorKind::Assert {
                 ref cond, ref msg, ..
@@ -1493,7 +1508,23 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             Some((ref dest, _target_block)) => {
                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
                 let category = match *dest {
-                    Place::Local(RETURN_PLACE) => ConstraintCategory::Return,
+                    Place::Local(RETURN_PLACE) => {
+                        if let Some(BorrowCheckContext {
+                            universal_regions: UniversalRegions {
+                                defining_ty: DefiningTy::Const(def_id, _),
+                                ..
+                            },
+                            ..
+                        }) = self.borrowck_context {
+                            if tcx.is_static(*def_id).is_some() {
+                                ConstraintCategory::UseAsStatic
+                            } else {
+                                ConstraintCategory::UseAsConst
+                            }
+                        } else {
+                            ConstraintCategory::Return
+                        }
+                    },
                     Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
                         ConstraintCategory::Boring
                     }
@@ -1538,18 +1569,24 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
         sig: &ty::FnSig<'tcx>,
         args: &[Operand<'tcx>],
         term_location: Location,
+        from_hir_call: bool,
     ) {
         debug!("check_call_inputs({:?}, {:?})", sig, args);
         if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.variadic) {
             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
         }
         for (n, (fn_arg, op_arg)) in sig.inputs().iter().zip(args).enumerate() {
             let op_arg_ty = op_arg.ty(mir, self.tcx());
+            let category = if from_hir_call {
+                ConstraintCategory::CallArgument
+            } else {
+                ConstraintCategory::Boring
+            };
             if let Err(terr) = self.sub_types(
                 op_arg_ty,
                 fn_arg,
                 term_location.to_locations(),
-                ConstraintCategory::CallArgument,
+                category,
             ) {
                 span_mirbug!(
                     self,