1 files changed, 48 insertions, 2 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index f4eee835f..cfe07156b 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -19,7 +19,7 @@ use std::{fmt, mem};
 use crate::{Name, AdtDef, type_ref::Mutability, db::HirDatabase, Trait, GenericParams};
 use display::{HirDisplay, HirFormatter};
 
-pub(crate) use lower::{TypableDef, type_for_def, type_for_field, callable_item_sig};
+pub(crate) use lower::{TypableDef, type_for_def, type_for_field, callable_item_sig, generic_predicates};
 pub(crate) use infer::{infer, InferenceResult, InferTy};
 pub use lower::CallableDef;
 
@@ -234,13 +234,42 @@ impl TraitRef {
     }
 }
 
+/// Like `generics::WherePredicate`, but with resolved types: A condition on the
+/// parameters of a generic item.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum GenericPredicate {
+    /// The given trait needs to be implemented for its type parameters.
+    Implemented(TraitRef),
+    /// We couldn't resolve the trait reference. (If some type parameters can't
+    /// be resolved, they will just be Unknown).
+    Error,
+}
+
+impl GenericPredicate {
+    pub fn is_error(&self) -> bool {
+        match self {
+            GenericPredicate::Error => true,
+            _ => false,
+        }
+    }
+
+    pub fn subst(self, substs: &Substs) -> GenericPredicate {
+        match self {
+            GenericPredicate::Implemented(trait_ref) => {
+                GenericPredicate::Implemented(trait_ref.subst(substs))
+            }
+            GenericPredicate::Error => self,
+        }
+    }
+}
+
 /// Basically a claim (currently not validated / checked) that the contained
 /// type / trait ref contains no inference variables; any inference variables it
 /// contained have been replaced by bound variables, and `num_vars` tells us how
 /// many there are. This is used to erase irrelevant differences between types
 /// before using them in queries.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub(crate) struct Canonical<T> {
+pub struct Canonical<T> {
     pub value: T,
     pub num_vars: usize,
 }
@@ -534,3 +563,20 @@ impl HirDisplay for Ty {
         Ok(())
     }
 }
+
+impl HirDisplay for TraitRef {
+    fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+        write!(
+            f,
+            "{}: {}",
+            self.substs[0].display(f.db),
+            self.trait_.name(f.db).unwrap_or_else(Name::missing)
+        )?;
+        if self.substs.len() > 1 {
+            write!(f, "<")?;
+            f.write_joined(&self.substs[1..], ", ")?;
+            write!(f, ">")?;
+        }
+        Ok(())
+    }
+}