Make nested ternary without parentheses a compile error

This was deprecated in PHP 7.4.

Author: nikic

UPGRADING

@@ -208,6 +208,8 @@ PHP 8.0 UPGRADE NOTES
     recognized as a namespaced name, `Foo \ Bar` will not. Conversely, reserved
     keywords are now permitted as namespace segments.
     RFC: https://wiki.php.net/rfc/namespaced_names_as_token
+  . Nested ternaries now require explicit parentheses.
+    RFC: https://wiki.php.net/rfc/ternary_associativity
 
 - COM:
   . Removed the ability to import case-insensitive constants from type

Zend/tests/ternary_associativity.phpt

@@ -1,30 +1,22 @@
 --TEST--
-Using ternary associativity is deprecated
+Allowed nested ternary cases
 --FILE--
 <?php
 
-1 ? 2 : 3 ? 4 : 5;   // deprecated
 (1 ? 2 : 3) ? 4 : 5; // ok
 1 ? 2 : (3 ? 4 : 5); // ok
 
-// While the associativity of ?: is also incorrect, it will not cause a
-// functional difference, only some unnecessary checks.
 1 ?: 2 ?: 3;   // ok
 (1 ?: 2) ?: 3; // ok
 1 ?: (2 ?: 3); // ok
 
-1 ?: 2 ? 3 : 4;   // deprecated
 (1 ?: 2) ? 3 : 4; // ok
 1 ?: (2 ? 3 : 4); // ok
 
-1 ? 2 : 3 ?: 4;   // deprecated
 (1 ? 2 : 3) ?: 4; // ok
 1 ? 2 : (3 ?: 4); // ok
 
 ?>
---EXPECTF--
-Deprecated: Unparenthesized `a ? b : c ? d : e` is deprecated. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` in %s on line 3
-
-Deprecated: Unparenthesized `a ?: b ? c : d` is deprecated. Use either `(a ?: b) ? c : d` or `a ?: (b ? c : d)` in %s on line 13
-
-Deprecated: Unparenthesized `a ? b : c ?: d` is deprecated. Use either `(a ? b : c) ?: d` or `a ? b : (c ?: d)` in %s on line 17
+===DONE===
+--EXPECT--
+===DONE===

Zend/tests/ternary_associativity_1.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Forbidden nested ternary, case 1
+--FILE--
+<?php
+
+1 ? 2 : 3 ? 4 : 5;
+
+?>
+--EXPECTF--
+Fatal error: Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` in %s on line %d

Zend/tests/ternary_associativity_2.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Forbidden nested ternary, case 2
+--FILE--
+<?php
+
+1 ?: 2 ? 3 : 4;
+
+?>
+--EXPECTF--
+Fatal error: Unparenthesized `a ?: b ? c : d` is not supported. Use either `(a ?: b) ? c : d` or `a ?: (b ? c : d)` in %s on line %d

Zend/tests/ternary_associativity_3.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Forbidden nested ternary, case 3
+--FILE--
+<?php
+
+1 ? 2 : 3 ?: 4;
+
+?>
+--EXPECTF--
+Fatal error: Unparenthesized `a ? b : c ?: d` is not supported. Use either `(a ? b : c) ?: d` or `a ? b : (c ?: d)` in %s on line %d

Zend/zend_compile.c

@@ -8234,18 +8234,18 @@ void zend_compile_conditional(znode *result, zend_ast *ast) /* {{{ */
 			&& cond_ast->attr != ZEND_PARENTHESIZED_CONDITIONAL) {
 		if (cond_ast->child[1]) {
 			if (true_ast) {
-				zend_error(E_DEPRECATED,
-					"Unparenthesized `a ? b : c ? d : e` is deprecated. "
+				zend_error(E_COMPILE_ERROR,
+					"Unparenthesized `a ? b : c ? d : e` is not supported. "
 					"Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)`");
 			} else {
-				zend_error(E_DEPRECATED,
-					"Unparenthesized `a ? b : c ?: d` is deprecated. "
+				zend_error(E_COMPILE_ERROR,
+					"Unparenthesized `a ? b : c ?: d` is not supported. "
 					"Use either `(a ? b : c) ?: d` or `a ? b : (c ?: d)`");
 			}
 		} else {
 			if (true_ast) {
-				zend_error(E_DEPRECATED,
-					"Unparenthesized `a ?: b ? c : d` is deprecated. "
+				zend_error(E_COMPILE_ERROR,
+					"Unparenthesized `a ?: b ? c : d` is not supported. "
 					"Use either `(a ?: b) ? c : d` or `a ?: (b ? c : d)`");
 			} else {
 				/* This case is harmless:  (a ?: b) ?: c always produces the same result