3 files changed, 127 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index f6283ab6d..fe259371f 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -577,6 +577,42 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
         Some(struct_.into())
     }
+
+    fn resolve_range_full(&self) -> Option<AdtId> {
+        let path = known::std_ops_range_full();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
+
+    fn resolve_range(&self) -> Option<AdtId> {
+        let path = known::std_ops_range();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
+
+    fn resolve_range_inclusive(&self) -> Option<AdtId> {
+        let path = known::std_ops_range_inclusive();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
+
+    fn resolve_range_from(&self) -> Option<AdtId> {
+        let path = known::std_ops_range_from();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
+
+    fn resolve_range_to(&self) -> Option<AdtId> {
+        let path = known::std_ops_range_to();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
+
+    fn resolve_range_to_inclusive(&self) -> Option<AdtId> {
+        let path = known::std_ops_range_to_inclusive();
+        let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
+        Some(struct_.into())
+    }
 }
 
 /// The ID of a type variable.
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 2f9ca4bbb..a00aa426a 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -415,6 +415,47 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
                 _ => Ty::Unknown,
             },
+            Expr::RangeFull => match self.resolve_range_full() {
+                Some(adt) => Ty::simple(TypeCtor::Adt(adt)),
+                None => Ty::Unknown,
+            },
+            Expr::Range { lhs, rhs } => {
+                let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
+                let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(lhs_ty));
+                match self.resolve_range() {
+                    Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), rhs_ty),
+                    None => Ty::Unknown,
+                }
+            }
+            Expr::RangeInclusive { lhs, rhs } => {
+                let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
+                let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(lhs_ty));
+                match self.resolve_range_inclusive() {
+                    Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), rhs_ty),
+                    None => Ty::Unknown,
+                }
+            }
+            Expr::RangeFrom { lhs } => {
+                let ty = self.infer_expr(*lhs, &Expectation::none());
+                match self.resolve_range_from() {
+                    Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                    None => Ty::Unknown,
+                }
+            }
+            Expr::RangeTo { rhs } => {
+                let ty = self.infer_expr(*rhs, &Expectation::none());
+                match self.resolve_range_to() {
+                    Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                    None => Ty::Unknown,
+                }
+            }
+            Expr::RangeToInclusive { rhs } => {
+                let ty = self.infer_expr(*rhs, &Expectation::none());
+                match self.resolve_range_to_inclusive() {
+                    Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                    None => Ty::Unknown,
+                }
+            }
             Expr::Index { base, index } => {
                 let _base_ty = self.infer_expr(*base, &Expectation::none());
                 let _index_ty = self.infer_expr(*index, &Expectation::none());
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index abbc1546c..4ba87e667 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -222,6 +222,56 @@ mod collections {
 }
 
 #[test]
+fn infer_ranges() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+fn test() {
+    let a = ..;
+    let b = 1..;
+    let c = ..2u32;
+    let d = 1..2usize;
+    let e = ..=10;
+    let f = 'a'..='z';
+
+    let t = (a, b, c, d, e, f);
+    t<|>;
+}
+
+//- /std.rs crate:std
+#[prelude_import] use prelude::*;
+mod prelude {}
+
+pub mod ops {
+    pub struct Range<Idx> {
+        pub start: Idx,
+        pub end: Idx,
+    }
+    pub struct RangeFrom<Idx> {
+        pub start: Idx,
+    }
+    struct RangeFull;
+    pub struct RangeInclusive<Idx> {
+        start: Idx,
+        end: Idx,
+        is_empty: u8,
+    }
+    pub struct RangeTo<Idx> {
+        pub end: Idx,
+    }
+    pub struct RangeToInclusive<Idx> {
+        pub end: Idx,
+    }
+}
+"#,
+    );
+    assert_eq!(
+        "(RangeFull, RangeFrom<i32>, RangeTo<u32>, Range<usize>, RangeToInclusive<i32>, RangeInclusive<char>)",
+        type_at_pos(&db, pos),
+    );
+}
+
+#[test]
 fn infer_while_let() {
     let (db, pos) = TestDB::with_position(
         r#"