From 5645c153e0379874d1f44ab149c3ec9257812692 Mon Sep 17 00:00:00 2001
From: Geoffry Song <goffrie@gmail.com>
Date: Fri, 15 Nov 2019 12:05:29 -0800
Subject: Attempt to implement typed accessors

---
 crates/ra_syntax/src/ast.rs                        |  2 +-
 crates/ra_syntax/src/ast/expr_extensions.rs        | 46 ++++++++++++++++++++++
 crates/ra_syntax/src/validation.rs                 |  8 +---
 .../parser/err/0038_endless_inclusive_range.txt    |  2 +-
 4 files changed, 50 insertions(+), 8 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/validation.rs b/crates/ra_syntax/src/validation.rs
index e01333e23..222ac15f8 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/crates/ra_syntax/src/validation.rs
@@ -230,14 +230,10 @@ fn validate_visibility(vis: ast::Visibility, errors: &mut Vec<SyntaxError>) {
 }
 
 fn validate_range_expr(expr: ast::RangeExpr, errors: &mut Vec<SyntaxError>) {
-    let last_child = match expr.syntax().last_child_or_token() {
-        Some(it) => it,
-        None => return,
-    };
-    if last_child.kind() == T![..=] {
+    if expr.op_kind() == Some(ast::RangeOp::Inclusive) && expr.end().is_none() {
         errors.push(SyntaxError::new(
             SyntaxErrorKind::InclusiveRangeMissingEnd,
-            last_child.text_range(),
+            expr.syntax().text_range(),
         ));
     }
 }
diff --git a/crates/ra_syntax/test_data/parser/err/0038_endless_inclusive_range.txt b/crates/ra_syntax/test_data/parser/err/0038_endless_inclusive_range.txt
index 749d53609..3810b9680 100644
--- a/crates/ra_syntax/test_data/parser/err/0038_endless_inclusive_range.txt
+++ b/crates/ra_syntax/test_data/parser/err/0038_endless_inclusive_range.txt
@@ -26,5 +26,5 @@ SOURCE_FILE@[0; 33)
         WHITESPACE@[30; 31) "\n"
         R_CURLY@[31; 32) "}"
   WHITESPACE@[32; 33) "\n"
-error [17; 20): An inclusive range must have an end expression
+error [16; 20): An inclusive range must have an end expression
 error [26; 29): An inclusive range must have an end expression
-- 
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