Add regex syntax inside of expansions

corpus/expressions.txt

@@ -33,6 +33,7 @@ The regex operator
 [[ "35d8b" =~ ^[0-9a-fA-F] ]]
 [[ $CMD =~ (^|;)update_terminal_cwd($|;) ]]
 [[ ! " ${completions[*]} " =~ " $alias_cmd " ]]
+! [[ "$a" =~ ^a|b\ *c|d$ ]]
 
 ---
 
@@ -46,7 +47,13 @@ The regex operator
   (bracket_command
     (word)
     (string (expansion (subscript (variable_name) (word))))
-    (string (simple_expansion (variable_name)))))
+    (string (simple_expansion (variable_name))))
+  (command
+    (command_name (word))
+    (word)
+    (string (simple_expansion (variable_name)))
+    (regex)
+    (word)))
 
 =============================
 Simple variable expansions
@@ -108,7 +115,7 @@ F="${G%% *}"
     (string (expansion (subscript (variable_name) (word)))))
   (variable_assignment
     (variable_name)
-    (string (expansion (variable_name) (word) (word))))
+    (string (expansion (variable_name) (regex) (word) (word))))
   (variable_assignment
     (variable_name)
     (string (expansion (variable_name) (word) (word)))))
@@ -118,7 +125,7 @@ Variable expansions in strings
 ===================================
 
 A="${A:-$B/c}"
-A="${b/$c/$d}"
+A="${b=$c/$d}"
 
 ---
 
@@ -139,6 +146,22 @@ A="${b/$c/$d}"
           (word)
           (simple_expansion (variable_name)))))))
 
+===================================
+Variable expansions with regexes
+===================================
+
+A=${B//:;;/$'\n'}
+
+# escaped space
+C=${D/;\ *;|}
+
+---
+
+(program
+  (variable_assignment (variable_name) (expansion (variable_name) (regex)))
+  (comment)
+  (variable_assignment (variable_name) (expansion (variable_name) (regex))))
+
 ===================================
 Other variable expansion operators
 ===================================

grammar.js

@@ -373,9 +373,13 @@ module.exports = grammar({
             $._simple_variable_name,
             $._special_variable_name
           ),
+          optional(seq(
+            token(prec(1, '/')),
+            alias($.regex_without_right_brace, $.regex)
+          )),
           repeat(choice(
             $._expression,
-            ':', ':?', '=', ':-', '%', '/', '-', '#'
+            ':', ':?', '=', ':-', '%', '-', '#'
           ))
         ),
       ),
@@ -404,7 +408,8 @@ module.exports = grammar({
       seq('\\', noneOf('\\s'))
     ))),
 
-    regex: $ => /\S+/,
+    regex: $ => /([^\s]|\\.)+/,
+    regex_without_right_brace: $ => /([^\s}]|\\.)+/,
 
     _terminator: $ => choice(';', ';;', '\n', '&')
   }