1 files changed, 47 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/regionck.rs b/compiler/rustc_typeck/src/check/regionck.rs
new file mode 100644
index 000000000..d49a6138f
--- /dev/null
+++ b/compiler/rustc_typeck/src/check/regionck.rs
@@ -0,0 +1,47 @@
+use crate::outlives::outlives_bounds::InferCtxtExt as _;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_hir as hir;
+use rustc_infer::infer::outlives::env::OutlivesEnvironment;
+use rustc_infer::infer::InferCtxt;
+use rustc_middle::ty::Ty;
+
+pub(crate) trait OutlivesEnvironmentExt<'tcx> {
+    fn add_implied_bounds(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        fn_sig_tys: FxHashSet<Ty<'tcx>>,
+        body_id: hir::HirId,
+    );
+}
+
+impl<'tcx> OutlivesEnvironmentExt<'tcx> for OutlivesEnvironment<'tcx> {
+    /// This method adds "implied bounds" into the outlives environment.
+    /// Implied bounds are outlives relationships that we can deduce
+    /// on the basis that certain types must be well-formed -- these are
+    /// either the types that appear in the function signature or else
+    /// the input types to an impl. For example, if you have a function
+    /// like
+    ///
+    /// ```
+    /// fn foo<'a, 'b, T>(x: &'a &'b [T]) { }
+    /// ```
+    ///
+    /// we can assume in the caller's body that `'b: 'a` and that `T:
+    /// 'b` (and hence, transitively, that `T: 'a`). This method would
+    /// add those assumptions into the outlives-environment.
+    ///
+    /// Tests: `src/test/ui/regions/regions-free-region-ordering-*.rs`
+    #[instrument(level = "debug", skip(self, infcx))]
+    fn add_implied_bounds<'a>(
+        &mut self,
+        infcx: &InferCtxt<'a, 'tcx>,
+        fn_sig_tys: FxHashSet<Ty<'tcx>>,
+        body_id: hir::HirId,
+    ) {
+        for ty in fn_sig_tys {
+            let ty = infcx.resolve_vars_if_possible(ty);
+            let implied_bounds = infcx.implied_outlives_bounds(self.param_env, body_id, ty);
+            self.add_outlives_bounds(Some(infcx), implied_bounds)
+        }
+    }
+}