4 files changed, 61 insertions, 1 deletions

diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index 1ec9881b9..277532a8c 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -16,7 +16,7 @@ use crate::{
 };
 
 pub use self::{
-    expr_extensions::{ArrayExprKind, BinOp, ElseBranch, LiteralKind, PrefixOp},
+    expr_extensions::{ArrayExprKind, BinOp, ElseBranch, LiteralKind, PrefixOp, RangeOp},
     extensions::{FieldKind, PathSegmentKind, SelfParamKind, StructKind, TypeBoundKind},
     generated::*,
     tokens::*,
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
index 25dbd0bed..7c53aa934 100644
--- a/crates/ra_syntax/src/ast/expr_extensions.rs
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -189,6 +189,52 @@ impl ast::BinExpr {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum RangeOp {
+    /// `..`
+    Exclusive,
+    /// `..=`
+    Inclusive,
+}
+
+impl ast::RangeExpr {
+    fn op_details(&self) -> Option<(usize, SyntaxToken, RangeOp)> {
+        self.syntax().children_with_tokens().enumerate().find_map(|(ix, child)| {
+            let token = child.into_token()?;
+            let bin_op = match token.kind() {
+                T![..] => RangeOp::Exclusive,
+                T![..=] => RangeOp::Inclusive,
+                _ => return None,
+            };
+            Some((ix, token, bin_op))
+        })
+    }
+
+    pub fn op_kind(&self) -> Option<RangeOp> {
+        self.op_details().map(|t| t.2)
+    }
+
+    pub fn op_token(&self) -> Option<SyntaxToken> {
+        self.op_details().map(|t| t.1)
+    }
+
+    pub fn start(&self) -> Option<ast::Expr> {
+        let op_ix = self.op_details()?.0;
+        self.syntax()
+            .children_with_tokens()
+            .take(op_ix)
+            .find_map(|it| ast::Expr::cast(it.into_node()?))
+    }
+
+    pub fn end(&self) -> Option<ast::Expr> {
+        let op_ix = self.op_details()?.0;
+        self.syntax()
+            .children_with_tokens()
+            .skip(op_ix + 1)
+            .find_map(|it| ast::Expr::cast(it.into_node()?))
+    }
+}
+
 impl ast::IndexExpr {
     pub fn base(&self) -> Option<ast::Expr> {
         children(self).nth(0)
diff --git a/crates/ra_syntax/src/syntax_error.rs b/crates/ra_syntax/src/syntax_error.rs
index 1f60a7aab..6c171df8d 100644
--- a/crates/ra_syntax/src/syntax_error.rs
+++ b/crates/ra_syntax/src/syntax_error.rs
@@ -83,6 +83,7 @@ pub enum SyntaxErrorKind {
     InvalidMatchInnerAttr,
     InvalidTupleIndexFormat,
     VisibilityNotAllowed,
+    InclusiveRangeMissingEnd,
 }
 
 impl fmt::Display for SyntaxErrorKind {
@@ -103,6 +104,9 @@ impl fmt::Display for SyntaxErrorKind {
             VisibilityNotAllowed => {
                 write!(f, "unnecessary visibility qualifier")
             }
+            InclusiveRangeMissingEnd => {
+                write!(f, "An inclusive range must have an end expression")
+            }
         }
     }
 }
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
index 2d596763e..222ac15f8 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/crates/ra_syntax/src/validation.rs
@@ -103,6 +103,7 @@ pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
                 ast::FieldExpr(it) => { validate_numeric_name(it.name_ref(), &mut errors) },
                 ast::RecordField(it) => { validate_numeric_name(it.name_ref(), &mut errors) },
                 ast::Visibility(it) => { validate_visibility(it, &mut errors) },
+                ast::RangeExpr(it) => { validate_range_expr(it, &mut errors) },
                 _ => (),
             }
         }
@@ -227,3 +228,12 @@ fn validate_visibility(vis: ast::Visibility, errors: &mut Vec<SyntaxError>) {
             .push(SyntaxError::new(SyntaxErrorKind::VisibilityNotAllowed, vis.syntax.text_range()))
     }
 }
+
+fn validate_range_expr(expr: ast::RangeExpr, errors: &mut Vec<SyntaxError>) {
+    if expr.op_kind() == Some(ast::RangeOp::Inclusive) && expr.end().is_none() {
+        errors.push(SyntaxError::new(
+            SyntaxErrorKind::InclusiveRangeMissingEnd,
+            expr.syntax().text_range(),
+        ));
+    }
+}