Consolidate string offset by reference errors

Use the same error message for all scenarios where a reference to
a string offset is acquired.

Author: nikic

Zend/tests/bug70089.phpt

@@ -31,5 +31,5 @@ try {
 --EXPECT--
 string(36) "Cannot use string offset as an array"
 string(27) "Cannot unset string offsets"
-string(41) "Only variables can be passed by reference"
+string(47) "Cannot create references to/from string offsets"
 string(41) "Cannot increment/decrement string offsets"

Zend/tests/bug73792.phpt

@@ -14,7 +14,7 @@ echo 'done';
 --EXPECTF--
 Warning: Illegal string offset "2bbb" in %s on line %d
 
-Fatal error: Uncaught Error: Cannot iterate on string offsets by reference in %sbug73792.php:4
+Fatal error: Uncaught Error: Cannot create references to/from string offsets in %s:%d
 Stack trace:
 #0 {main}
   thrown in %sbug73792.php on line 4

Zend/tests/string_offset_errors.phpt

@@ -8,6 +8,11 @@ function &test() : string {
     return $str[0];
 }
 
+function &gen() {
+    $str = "foo";
+    yield $str[0];
+}
+
 try {
     test();
 } catch (Error $e) {
@@ -21,7 +26,14 @@ try {
     echo $e->getMessage(), "\n";
 }
 
+try {
+    foreach (gen() as $v) {}
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
 ?>
 --EXPECT--
-Cannot return string offsets by reference
+Cannot create references to/from string offsets
+Cannot create references to/from string offsets
 Cannot create references to/from string offsets

Zend/zend_execute.c

@@ -1585,25 +1585,17 @@ ZEND_API ZEND_COLD void zend_wrong_string_offset_error(void)
 					case ZEND_ADD_ARRAY_ELEMENT:
 					case ZEND_INIT_ARRAY:
 					case ZEND_MAKE_REF:
-						msg = "Cannot create references to/from string offsets";
-						break;
 					case ZEND_RETURN_BY_REF:
 					case ZEND_VERIFY_RETURN_TYPE:
-						msg = "Cannot return string offsets by reference";
-						break;
-					case ZEND_UNSET_DIM:
-						msg = "Cannot unset string offsets";
-						break;
 					case ZEND_YIELD:
-						msg = "Cannot yield string offsets by reference";
-						break;
 					case ZEND_SEND_REF:
 					case ZEND_SEND_VAR_EX:
 					case ZEND_SEND_FUNC_ARG:
-						msg = "Only variables can be passed by reference";
-						break;
 					case ZEND_FE_RESET_RW:
-						msg = "Cannot iterate on string offsets by reference";
+						msg = "Cannot create references to/from string offsets";
+						break;
+					case ZEND_UNSET_DIM:
+						msg = "Cannot unset string offsets";
 						break;
 					EMPTY_SWITCH_DEFAULT_CASE();
 				}