Allow prefixed string expression (regex strings like re'/foo/') in constant initializer positions

Summary: These are constants.

Reviewed By: madgen

Differential Revision: D89828200

fbshipit-source-id: a8be49c24d6df8d5aac9160018f42baab25bbc80

Author: viratyosin

hphp/hack/src/parser/rust_parser_errors.rs

@@ -4827,6 +4827,14 @@ impl<'a, State: 'a + Clone> ParserErrors<'a, State> {
                     default(self);
                 }
             }
+            PrefixedStringExpression(x) => {
+                // Allow prefixed strings (e.g., re'/foo/') in constant expressions for runtime only
+                if self.env.is_typechecker() {
+                    default(self)
+                } else {
+                    self.check_constant_expression(&x.str, static_allowed)
+                }
+            }
             _ => default(self),
         }
     }

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_default_values.php

@@ -0,0 +1,7 @@
+<?hh
+
+function test_with_default(
+  HH\Lib\Regex\Pattern<shape(...)> $pattern = re'/default/',
+): void {
+  echo $pattern;
+}

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_default_values.php.exp

@@ -0,0 +1 @@
+No errors

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_enum_values.php

@@ -0,0 +1,5 @@
+<?hh
+
+enum PatternEnum: HH\Lib\Regex\Pattern<shape(...)> as string {
+  SIMPLE = re'/simple/';
+}

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_enum_values.php.exp

@@ -0,0 +1,4 @@
+ERROR: File "prefixed_string_enum_values.php", line 4, characters 12-23:
+Expected constant expression for initializer (Parsing[1002])
+ERROR: File "prefixed_string_enum_values.php", line 4, characters 12-23:
+Illegal constant value (Naming[2023])

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_in_constants.php

@@ -0,0 +1,7 @@
+<?hh
+
+class MyClass {
+  const HH\Lib\Regex\Pattern<shape(...)> PATTERN = re'/[a-z]+/';
+  const HH\Lib\Regex\Pattern<shape('x' => string, ...)> NAMED =
+    re'/(?P<x>[a-z]+)/';
+}

hphp/hack/test/typecheck/re_prefixed_string/prefixed_string_in_constants.php.exp

@@ -0,0 +1,8 @@
+ERROR: File "prefixed_string_in_constants.php", line 4, characters 52-63:
+Expected constant expression for initializer (Parsing[1002])
+ERROR: File "prefixed_string_in_constants.php", line 6, characters 5-23:
+Expected constant expression for initializer (Parsing[1002])
+ERROR: File "prefixed_string_in_constants.php", line 4, characters 52-63:
+Illegal constant value (Naming[2023])
+ERROR: File "prefixed_string_in_constants.php", line 6, characters 5-23:
+Illegal constant value (Naming[2023])

hphp/test/slow/prefixed_string/prefixed_string.php

@@ -1,7 +1,6 @@
 <?hh
 
-function f(): void {
-  $x = re"blah blah\n";
+function f(string $x = re"blah blah\n"): void {
   echo($x);
   $s1 = "Be";
   $s2 = "diff";