Support for string escapes

grammar.js

@@ -1,4 +1,4 @@
 const PREC = {
   comment: 1,
   using_directive: 2,
   control: 1,
@@ -32,19 +32,24 @@
   externals: $ => [
     $._automatic_semicolon,
     $._indent,
+    $._outdent,
+    $._simple_string_start,
+    $._simple_string_middle,
+    $._simple_multiline_string_start,
     $._interpolated_string_middle,
-    $._interpolated_string_end,
     $._interpolated_multiline_string_middle,
-    $._interpolated_multiline_string_end,
-    $._outdent,
-    $._simple_multiline_string,
-    $._simple_string,
+    $._raw_string_start,
+    $._raw_string_middle,
+    $._raw_string_multiline_middle,
+    $._single_line_string_end,
+    $._multiline_string_end,
     "else",
     "catch",
     "finally",
     "extends",
     "derives",
     "with",
+    $.error_sentinel,
   ],
 
   inline: $ => [
@@ -209,7 +214,7 @@
           "package",
           field("name", $.package_identifier),
           // This is slightly more permissive than the EBNF in that it allows any
-          // kind of delcaration inside of the package blocks. As we're more
+          // kind of declaration inside of the package blocks. As we're more
           // concerned with the structure rather than the validity of the program
           // we'll allow it.
           field("body", optional($.template_body)),
@@ -677,7 +682,7 @@
           // In theory structural_type should just be added to simple_type,
           // but doing so increases the state of template_body to 4000
           $._structural_type,
-          // This adds _simple_type, but not the above intentionall/y.
+          // This adds _simple_type, but not the above intentionally.
           seq($._simple_type, field("arguments", $.arguments)),
           seq($._annotated_type, field("arguments", $.arguments)),
           seq($.compound_type, field("arguments", $.arguments)),
@@ -936,7 +941,7 @@
         ),
       ),
 
     tuple_type: $ => seq("(", trailingCommaSep1($._type), ")"),
 
     named_tuple_type: $ => seq("(", trailingCommaSep1($.name_and_type), ")"),
 
@@ -1540,14 +1545,14 @@
 
     /**
      * Regex patterns created to avoid matching // comments and /* comment starts.
-     * This could technically match illeagal tokens such as val ?// = 1
+     * This could technically match illegal tokens such as val ?// = 1
      */
     operator_identifier: $ =>
       token(
         choice(
           // opchar minus colon, equal, at
           // Technically speaking, Sm (Math symbols https://www.compart.com/en/unicode/category/Sm)
-          // should be allowed as a single-characeter opchar, however, it includes `=`,
+          // should be allowed as a single-character opchar, however, it includes `=`,
           // so we should to avoid that to prevent bad parsing of `=` as infix term or type.
           /[\-!#%&*+\/\\<>?\u005e\u007c~\u00ac\u00b1\u00d7\u00f7\u2190-\u2194\p{So}]/,
           seq(
@@ -1616,7 +1621,7 @@
             choice(
               seq(
                 "\\",
-                choice(/[^xu]/, /uu?[0-9a-fA-F]{4}/, /x[0-9a-fA-F]{2}/),
+                choice(/[^xu]/, /[uU]+[0-9a-fA-F]{4}/, /x[0-9a-fA-F]{2}/),
               ),
               /[^\\'\n]/,
             ),
@@ -1625,14 +1630,13 @@
         ),
       ),
 
-    interpolated_string_expression: $ =>
-      seq(field("interpolator", $.identifier), $.interpolated_string),
-
-    _interpolated_string_start: $ => '"',
-
-    _interpolated_multiline_string_start: $ => '"""',
+    interpolated_string_expression: $ => 
+        choice(
+          seq(field("interpolator", alias($._raw_string_start, $.identifier)), alias($._raw_string, $.interpolated_string)),
+          seq(field("interpolator", $.identifier), $.interpolated_string),
+      ),
 
-    _dollar_escape: $ => seq("$", choice("$", '"')),
+    _dollar_escape: $ => alias(token(seq("$", choice("$", '"'))), $.escape_sequence),
 
     _aliased_interpolation_identifier: $ =>
       alias($._interpolation_identifier, $.identifier),
@@ -1643,28 +1647,88 @@
     interpolated_string: $ =>
       choice(
         seq(
-          $._interpolated_string_start,
+          token.immediate('"'),
           repeat(
             seq(
               $._interpolated_string_middle,
-              choice($._dollar_escape, $.interpolation),
+              choice($._dollar_escape, $.interpolation, $.escape_sequence),
             ),
           ),
-          $._interpolated_string_end,
+          $._single_line_string_end,
         ),
         seq(
-          $._interpolated_multiline_string_start,
+          token.immediate('"""'),
           repeat(
             seq(
               $._interpolated_multiline_string_middle,
+              // Multiline strings ignore escape sequences
               choice($._dollar_escape, $.interpolation),
             ),
           ),
-          $._interpolated_multiline_string_end,
+          $._multiline_string_end,
+        ),
+      ),
+
+    // We need to handle single-line raw strings separately from interpolated strings,
+    // because raw strings are not parsed for escape sequences. For example, raw strings 
+    // are often used for regular expressions, which contain backslashes that would
+    // be invalid if parsed as escape sequences. We do not special case multiline
+    // raw strings, because multiline strings do not parse escape sequences anyway.
+    // Scala handles multiline raw strings identically to other multiline interpolated,
+    // so we could parse them as interpolated strings, but I think the code is cleaner
+    // if we maintain the distinction.
+    _raw_string: $ => 
+      choice(
+        seq(
+          $._simple_string_start,
+          seq(
+            repeat(
+              seq(
+                $._raw_string_middle,
+                choice($._dollar_escape, $.interpolation),
+              ),
+            ),
+            $._single_line_string_end,
+          ), 
+        ),
+        seq(
+          $._simple_multiline_string_start,
+          repeat(
+            seq(
+              $._raw_string_multiline_middle,
+              choice($._dollar_escape, $.interpolation),
+            )
+          ),
+          $._multiline_string_end,
         ),
       ),
 
-    string: $ => choice($._simple_string, $._simple_multiline_string),
+    escape_sequence: _ => token.immediate(seq(
+      '\\',
+      choice(
+        /[tbnrf"'\\]/,
+        // The Java spec allows any number of u's and U's at the start of a unicode escape.
+        /[uU]+[0-9a-fA-F]{4}/,
+        // Octals are not allowed in Scala 3, but are allowed in Scala 2. tree-sitter 
+        // does not have a mechanism for distinguishing between different versions of a
+        // language, so I think it makes sense to allow them. Maybe in the future we
+        // should move them to a `deprecated` syntax node?
+        /[0-3]?[0-7]{1,2}/,
+      ),
+    )),
+
+    string: $ => choice(
+      seq(
+        $._simple_string_start,
+        repeat(seq($._simple_string_middle, $.escape_sequence)),
+        $._single_line_string_end,
+      ),
+      seq(
+        $._simple_multiline_string_start,
+        /// Multiline strings ignore escape sequences
+        $._multiline_string_end,
+      ),
+    ),
 
     _semicolon: $ => choice(";", $._automatic_semicolon),