2 files changed, 77 insertions, 9 deletions

diff --git a/crates/ra_ide/src/syntax_highlighting/html.rs b/crates/ra_ide/src/syntax_highlighting/html.rs
index 4496529a1..010db4017 100644
--- a/crates/ra_ide/src/syntax_highlighting/html.rs
+++ b/crates/ra_ide/src/syntax_highlighting/html.rs
@@ -1,11 +1,9 @@
 //! Renders a bit of code as HTML.
 
 use ra_db::SourceDatabase;
-use ra_syntax::{AstNode, TextUnit};
+use ra_syntax::{AstNode, TextRange, TextSize};
 
-use crate::{FileId, RootDatabase};
-
-use super::highlight;
+use crate::{syntax_highlighting::highlight, FileId, RootDatabase};
 
 pub(crate) fn highlight_as_html(db: &RootDatabase, file_id: FileId, rainbow: bool) -> String {
     let parse = db.parse(file_id);
@@ -23,17 +21,17 @@ pub(crate) fn highlight_as_html(db: &RootDatabase, file_id: FileId, rainbow: boo
 
     let ranges = highlight(db, file_id, None);
     let text = parse.tree().syntax().to_string();
-    let mut prev_pos = TextUnit::from(0);
+    let mut prev_pos = TextSize::from(0);
     let mut buf = String::new();
     buf.push_str(&STYLE);
     buf.push_str("<pre><code>");
     for range in &ranges {
         if range.range.start() > prev_pos {
-            let curr = &text[prev_pos.to_usize()..range.range.start().to_usize()];
+            let curr = &text[TextRange::new(prev_pos, range.range.start())];
             let text = html_escape(curr);
             buf.push_str(&text);
         }
-        let curr = &text[range.range.start().to_usize()..range.range.end().to_usize()];
+        let curr = &text[TextRange::new(range.range.start(), range.range.end())];
 
         let class = range.highlight.to_string().replace('.', " ");
         let color = match (rainbow, range.binding_hash) {
@@ -47,7 +45,7 @@ pub(crate) fn highlight_as_html(db: &RootDatabase, file_id: FileId, rainbow: boo
         prev_pos = range.range.end();
     }
     // Add the remaining (non-highlighted) text
-    let curr = &text[prev_pos.to_usize()..];
+    let curr = &text[TextRange::new(prev_pos, TextSize::of(&text))];
     let text = html_escape(curr);
     buf.push_str(&text);
     buf.push_str("</code></pre>");
diff --git a/crates/ra_ide/src/syntax_highlighting/tests.rs b/crates/ra_ide/src/syntax_highlighting/tests.rs
index 73611e23a..d2926ba78 100644
--- a/crates/ra_ide/src/syntax_highlighting/tests.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tests.rs
@@ -126,7 +126,7 @@ fn test_ranges() {
 
     // The "x"
     let highlights = &analysis
-        .highlight_range(FileRange { file_id, range: TextRange::offset_len(82.into(), 1.into()) })
+        .highlight_range(FileRange { file_id, range: TextRange::at(82.into(), 1.into()) })
         .unwrap();
 
     assert_eq!(&highlights[0].highlight.to_string(), "field.declaration");
@@ -168,3 +168,73 @@ macro_rules! test {}
     );
     let _ = analysis.highlight(file_id).unwrap();
 }
+
+#[test]
+fn test_string_highlighting() {
+    // The format string detection is based on macro-expansion,
+    // thus, we have to copy the macro definition from `std`
+    let (analysis, file_id) = single_file(
+        r#"
+macro_rules! println {
+    ($($arg:tt)*) => ({
+        $crate::io::_print($crate::format_args_nl!($($arg)*));
+    })
+}
+#[rustc_builtin_macro]
+macro_rules! format_args_nl {
+    ($fmt:expr) => {{ /* compiler built-in */ }};
+    ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
+}
+
+fn main() {
+    // from https://doc.rust-lang.org/std/fmt/index.html
+    println!("Hello");                 // => "Hello"
+    println!("Hello, {}!", "world");   // => "Hello, world!"
+    println!("The number is {}", 1);   // => "The number is 1"
+    println!("{:?}", (3, 4));          // => "(3, 4)"
+    println!("{value}", value=4);      // => "4"
+    println!("{} {}", 1, 2);           // => "1 2"
+    println!("{:04}", 42);             // => "0042" with leading zerosV
+    println!("{1} {} {0} {}", 1, 2);   // => "2 1 1 2"
+    println!("{argument}", argument = "test");   // => "test"
+    println!("{name} {}", 1, name = 2);          // => "2 1"
+    println!("{a} {c} {b}", a="a", b='b', c=3);  // => "a 3 b"
+    println!("Hello {:5}!", "x");
+    println!("Hello {:1$}!", "x", 5);
+    println!("Hello {1:0$}!", 5, "x");
+    println!("Hello {:width$}!", "x", width = 5);
+    println!("Hello {:<5}!", "x");
+    println!("Hello {:-<5}!", "x");
+    println!("Hello {:^5}!", "x");
+    println!("Hello {:>5}!", "x");
+    println!("Hello {:+}!", 5);
+    println!("{:#x}!", 27);
+    println!("Hello {:05}!", 5);
+    println!("Hello {:05}!", -5);
+    println!("{:#010x}!", 27);
+    println!("Hello {0} is {1:.5}", "x", 0.01);
+    println!("Hello {1} is {2:.0$}", 5, "x", 0.01);
+    println!("Hello {0} is {2:.1$}", "x", 5, 0.01);
+    println!("Hello {} is {:.*}",    "x", 5, 0.01);
+    println!("Hello {} is {2:.*}",   "x", 5, 0.01);
+    println!("Hello {} is {number:.prec$}", "x", prec = 5, number = 0.01);
+    println!("{}, `{name:.*}` has 3 fractional digits", "Hello", 3, name=1234.56);
+    println!("{}, `{name:.*}` has 3 characters", "Hello", 3, name="1234.56");
+    println!("{}, `{name:>8.*}` has 3 right-aligned characters", "Hello", 3, name="1234.56");
+    println!("Hello {{}}");
+    println!("{{ Hello");
+
+    println!(r"Hello, {}!", "world");
+
+    println!("{\x41}", A = 92);
+    println!("{ничоси}", ничоси = 92);
+}"#
+        .trim(),
+    );
+
+    let dst_file = project_dir().join("crates/ra_ide/src/snapshots/highlight_strings.html");
+    let actual_html = &analysis.highlight_as_html(file_id, false).unwrap();
+    let expected_html = &read_text(&dst_file);
+    fs::write(dst_file, &actual_html).unwrap();
+    assert_eq_text!(expected_html, actual_html);
+}