7 files changed, 185 insertions, 1 deletions

diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 331736cb2..be1eaa523 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -429,10 +429,19 @@ where
                 let index = self.collect_expr_opt(e.index());
                 self.alloc_expr(Expr::Index { base, index }, syntax_ptr)
             }
+            ast::Expr::RangeExpr(e) => {
+                let lhs = e.start().map(|lhs| self.collect_expr(lhs));
+                let rhs = e.end().map(|rhs| self.collect_expr(rhs));
+                match e.op_kind() {
+                    Some(range_type) => {
+                        self.alloc_expr(Expr::Range { lhs, rhs, range_type }, syntax_ptr)
+                    }
+                    None => self.alloc_expr(Expr::Missing, syntax_ptr),
+                }
+            }
 
             // FIXME implement HIR for these:
             ast::Expr::Label(_e) => self.alloc_expr(Expr::Missing, syntax_ptr),
-            ast::Expr::RangeExpr(_e) => self.alloc_expr(Expr::Missing, syntax_ptr),
             ast::Expr::MacroCall(e) => match self.expander.enter_expand(self.db, e) {
                 Some((mark, expansion)) => {
                     let id = self.collect_expr(expansion);
diff --git a/crates/ra_hir_def/src/expr.rs b/crates/ra_hir_def/src/expr.rs
index 04c1d8f69..6fad80a8d 100644
--- a/crates/ra_hir_def/src/expr.rs
+++ b/crates/ra_hir_def/src/expr.rs
@@ -14,6 +14,7 @@
 
 use hir_expand::name::Name;
 use ra_arena::{impl_arena_id, RawId};
+use ra_syntax::ast::RangeOp;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt},
@@ -130,6 +131,11 @@ pub enum Expr {
         rhs: ExprId,
         op: Option<BinaryOp>,
     },
+    Range {
+        lhs: Option<ExprId>,
+        rhs: Option<ExprId>,
+        range_type: RangeOp,
+    },
     Index {
         base: ExprId,
         index: ExprId,
@@ -288,6 +294,14 @@ impl Expr {
                 f(*lhs);
                 f(*rhs);
             }
+            Expr::Range { lhs, rhs, .. } => {
+                if let Some(lhs) = rhs {
+                    f(*lhs);
+                }
+                if let Some(rhs) = lhs {
+                    f(*rhs);
+                }
+            }
             Expr::Index { base, index } => {
                 f(*base);
                 f(*index);
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 10688df4d..ff252fe44 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -409,6 +409,36 @@ pub mod known {
         Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::TRY_TYPE])
     }
 
+    pub fn std_ops_range() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::RANGE_TYPE])
+    }
+
+    pub fn std_ops_range_from() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::RANGE_FROM_TYPE])
+    }
+
+    pub fn std_ops_range_full() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::RANGE_FULL_TYPE])
+    }
+
+    pub fn std_ops_range_inclusive() -> Path {
+        Path::from_simple_segments(
+            PathKind::Abs,
+            vec![name::STD, name::OPS, name::RANGE_INCLUSIVE_TYPE],
+        )
+    }
+
+    pub fn std_ops_range_to() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::RANGE_TO_TYPE])
+    }
+
+    pub fn std_ops_range_to_inclusive() -> Path {
+        Path::from_simple_segments(
+            PathKind::Abs,
+            vec![name::STD, name::OPS, name::RANGE_TO_INCLUSIVE_TYPE],
+        )
+    }
+
     pub fn std_result_result() -> Path {
         Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::RESULT, name::RESULT_TYPE])
     }
diff --git a/crates/ra_hir_expand/src/name.rs b/crates/ra_hir_expand/src/name.rs
index 7824489d7..05ba37070 100644
--- a/crates/ra_hir_expand/src/name.rs
+++ b/crates/ra_hir_expand/src/name.rs
@@ -140,6 +140,12 @@ pub const RESULT_TYPE: Name = Name::new_inline_ascii(6, b"Result");
 pub const OUTPUT_TYPE: Name = Name::new_inline_ascii(6, b"Output");
 pub const TARGET_TYPE: Name = Name::new_inline_ascii(6, b"Target");
 pub const BOX_TYPE: Name = Name::new_inline_ascii(3, b"Box");
+pub const RANGE_FROM_TYPE: Name = Name::new_inline_ascii(9, b"RangeFrom");
+pub const RANGE_FULL_TYPE: Name = Name::new_inline_ascii(9, b"RangeFull");
+pub const RANGE_INCLUSIVE_TYPE: Name = Name::new_inline_ascii(14, b"RangeInclusive");
+pub const RANGE_TO_INCLUSIVE_TYPE: Name = Name::new_inline_ascii(16, b"RangeToInclusive");
+pub const RANGE_TO_TYPE: Name = Name::new_inline_ascii(7, b"RangeTo");
+pub const RANGE_TYPE: Name = Name::new_inline_ascii(5, b"Range");
 
 // Builtin Macros
 pub const FILE_MACRO: Name = Name::new_inline_ascii(4, b"file");
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..4014f4732 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -12,6 +12,7 @@ use hir_def::{
     AdtId, ContainerId, Lookup, StructFieldId,
 };
 use hir_expand::name::{self, Name};
+use ra_syntax::ast::RangeOp;
 
 use crate::{
     autoderef, db::HirDatabase, method_resolution, op, traits::InEnvironment, utils::variant_data,
@@ -415,6 +416,44 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
                 _ => Ty::Unknown,
             },
+            Expr::Range { lhs, rhs, range_type } => {
+                let lhs_ty = lhs.map(|e| self.infer_expr(e, &Expectation::none()));
+                let rhs_expect = lhs_ty
+                    .as_ref()
+                    .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
+                let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
+                match (range_type, lhs_ty, rhs_ty) {
+                    (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
+                        Some(adt) => Ty::simple(TypeCtor::Adt(adt)),
+                        None => Ty::Unknown,
+                    },
+                    (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
+                        Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                        None => Ty::Unknown,
+                    },
+                    (RangeOp::Inclusive, None, Some(ty)) => {
+                        match self.resolve_range_to_inclusive() {
+                            Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                            None => Ty::Unknown,
+                        }
+                    }
+                    (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
+                        Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                        None => Ty::Unknown,
+                    },
+                    (RangeOp::Inclusive, Some(_), Some(ty)) => {
+                        match self.resolve_range_inclusive() {
+                            Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                            None => Ty::Unknown,
+                        }
+                    }
+                    (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
+                        Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
+                        None => Ty::Unknown,
+                    },
+                    (RangeOp::Inclusive, _, 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#"