3 files changed, 23 insertions, 8 deletions

diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index ae8829807..9f6f1cc53 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -112,10 +112,14 @@ pub fn expr_prefix(op: SyntaxKind, expr: ast::Expr) -> ast::Expr {
     let token = token(op);
     expr_from_text(&format!("{}{}", token, expr.syntax()))
 }
-pub fn expr_from_text(text: &str) -> ast::Expr {
+fn expr_from_text(text: &str) -> ast::Expr {
     ast_from_text(&format!("const C: () = {};", text))
 }
 
+pub fn try_expr_from_text(text: &str) -> Option<ast::Expr> {
+    try_ast_from_text(&format!("const C: () = {};", text))
+}
+
 pub fn bind_pat(name: ast::Name) -> ast::BindPat {
     return from_text(name.text());
 
@@ -239,6 +243,16 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
     node
 }
 
+fn try_ast_from_text<N: AstNode>(text: &str) -> Option<N> {
+    let parse = SourceFile::parse(text);
+    let node = parse.tree().syntax().descendants().find_map(N::cast)?;
+    let node = node.syntax().clone();
+    let node = unroot(node);
+    let node = N::cast(node).unwrap();
+    assert_eq!(node.syntax().text_range().start(), 0.into());
+    Some(node)
+}
+
 fn unroot(n: SyntaxNode) -> SyntaxNode {
     SyntaxNode::new_root(n.green().clone())
 }
diff --git a/crates/ra_syntax/src/parsing/lexer.rs b/crates/ra_syntax/src/parsing/lexer.rs
index f2684c852..d1baaa607 100644
--- a/crates/ra_syntax/src/parsing/lexer.rs
+++ b/crates/ra_syntax/src/parsing/lexer.rs
@@ -65,7 +65,7 @@ pub fn tokenize(text: &str) -> (Vec<Token>, Vec<SyntaxError>) {
 /// Beware that unescape errors are not checked at tokenization time.
 pub fn lex_single_syntax_kind(text: &str) -> Option<(SyntaxKind, Option<SyntaxError>)> {
     lex_first_token(text)
-        .filter(|(token, _)| token.len.to_usize() == text.len())
+        .filter(|(token, _)| token.len == TextUnit::of_str(text))
         .map(|(token, error)| (token.kind, error))
 }
 
@@ -75,7 +75,7 @@ pub fn lex_single_syntax_kind(text: &str) -> Option<(SyntaxKind, Option<SyntaxEr
 /// Beware that unescape errors are not checked at tokenization time.
 pub fn lex_single_valid_syntax_kind(text: &str) -> Option<SyntaxKind> {
     lex_first_token(text)
-        .filter(|(token, error)| !error.is_some() && token.len.to_usize() == text.len())
+        .filter(|(token, error)| !error.is_some() && token.len == TextUnit::of_str(text))
         .map(|(token, _error)| token.kind)
 }
 
diff --git a/crates/ra_syntax/src/tests.rs b/crates/ra_syntax/src/tests.rs
index 912e6aec0..6a8cb6bb5 100644
--- a/crates/ra_syntax/src/tests.rs
+++ b/crates/ra_syntax/src/tests.rs
@@ -5,7 +5,7 @@ use std::{
 
 use test_utils::{collect_tests, dir_tests, project_dir, read_text};
 
-use crate::{fuzz, tokenize, SourceFile, SyntaxError, Token};
+use crate::{fuzz, tokenize, SourceFile, SyntaxError, TextRange, TextUnit, Token};
 
 #[test]
 fn lexer_tests() {
@@ -34,6 +34,7 @@ fn main() {
     "##;
 
     let parse = SourceFile::parse(code);
+    // eprintln!("{:#?}", parse.syntax_node());
     assert!(parse.ok().is_ok());
 }
 
@@ -120,11 +121,11 @@ fn assert_errors_are_absent(errors: &[SyntaxError], path: &Path) {
 
 fn dump_tokens_and_errors(tokens: &[Token], errors: &[SyntaxError], text: &str) -> String {
     let mut acc = String::new();
-    let mut offset = 0;
+    let mut offset = TextUnit::from_usize(0);
     for token in tokens {
-        let token_len = token.len.to_usize();
-        let token_text = &text[offset..offset + token_len];
-        offset += token_len;
+        let token_len = token.len;
+        let token_text = &text[TextRange::offset_len(offset, token.len)];
+        offset += token.len;
         writeln!(acc, "{:?} {} {:?}", token.kind, token_len, token_text).unwrap();
     }
     for err in errors {