zend_language_scanner: Lex clone as identifier when followed by (

This greatly simplifies the parser to support `clone()` as a function and
effectively reverts php#18938.

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>

Author: TimWolla

Zend/zend_language_parser.y

@@ -259,7 +259,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %type <ast> unprefixed_use_declarations const_decl inner_statement
 %type <ast> expr optional_expr while_statement for_statement foreach_variable
 %type <ast> foreach_statement declare_statement finally_statement unset_variable variable
-%type <ast> extends_from parameter optional_type_without_static argument argument_no_expr global_var
+%type <ast> extends_from parameter optional_type_without_static argument global_var
 %type <ast> static_var class_statement trait_adaptation trait_precedence trait_alias
 %type <ast> absolute_trait_method_reference trait_method_reference property echo_expr
 %type <ast> new_dereferenceable new_non_dereferenceable anonymous_class class_name class_name_reference simple_variable
@@ -287,7 +287,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %type <ast> enum_declaration_statement enum_backing_type enum_case enum_case_expr
 %type <ast> function_name non_empty_member_modifiers
 %type <ast> property_hook property_hook_list optional_property_hook_list hooked_property property_hook_body
-%type <ast> optional_parameter_list clone_argument_list non_empty_clone_argument_list
+%type <ast> optional_parameter_list
 
 %type <num> returns_ref function fn is_reference is_variadic property_modifiers property_hook_modifiers
 %type <num> method_modifiers class_const_modifiers member_modifier optional_cpp_modifiers
@@ -914,42 +914,13 @@ non_empty_argument_list:
 			{ $$ = zend_ast_list_add($1, $3); }
 ;
 
-/* `clone_argument_list` is necessary to resolve a parser ambiguity (shift-reduce conflict)
- * of `clone($expr)`, which could either be parsed as a function call with `$expr` as the first
- * argument or as a use of the `clone` language construct with an expression with useless
- * parenthesis. Both would be valid and result in the same AST / the same semantics.
- * `clone_argument_list` is defined in a way that an `expr` in the first position needs to
- * be followed by a `,` which is not valid syntax for a parenthesized `expr`, ensuring
- * that calling `clone()` with a single unnamed parameter is handled by the language construct
- * syntax.
- */
-clone_argument_list:
-		'(' ')'	{ $$ = zend_ast_create_list(0, ZEND_AST_ARG_LIST); }
-	|	'(' non_empty_clone_argument_list possible_comma ')' { $$ = $2; }
-	|	'(' expr ',' ')' { $$ = zend_ast_create_list(1, ZEND_AST_ARG_LIST, $2); }
-	|	'(' T_ELLIPSIS ')' { $$ = zend_ast_create_fcc(); }
-;
-
-non_empty_clone_argument_list:
-		expr ',' argument
-			{ $$ = zend_ast_create_list(2, ZEND_AST_ARG_LIST, $1, $3); }
-	|	argument_no_expr
-			{ $$ = zend_ast_create_list(1, ZEND_AST_ARG_LIST, $1); }
-	|	non_empty_clone_argument_list ',' argument
-			{ $$ = zend_ast_list_add($1, $3); }
-;
-
-argument_no_expr:
-		identifier ':' expr
+argument:
+		expr				{ $$ = $1; }
+	|	identifier ':' expr
 			{ $$ = zend_ast_create(ZEND_AST_NAMED_ARG, $1, $3); }
 	|	T_ELLIPSIS expr	{ $$ = zend_ast_create(ZEND_AST_UNPACK, $2); }
 ;
 
-argument:
-		expr { $$ = $1; }
-	|	argument_no_expr { $$ = $1; }
-;
-
 global_var_list:
 		global_var_list ',' global_var { $$ = zend_ast_list_add($1, $3); }
 	|	global_var { $$ = zend_ast_create_list(1, ZEND_AST_STMT_LIST, $1); }
@@ -1257,11 +1228,6 @@ expr:
 			{ $$ = zend_ast_create(ZEND_AST_ASSIGN, $1, $3); }
 	|	variable '=' ampersand variable
 			{ $$ = zend_ast_create(ZEND_AST_ASSIGN_REF, $1, $4); }
-	|	T_CLONE clone_argument_list {
-			zend_ast *name = zend_ast_create_zval_from_str(ZSTR_KNOWN(ZEND_STR_CLONE));
-			name->attr = ZEND_NAME_FQ;
-			$$ = zend_ast_create(ZEND_AST_CALL, name, $2);
-		}
 	|	T_CLONE expr {
 			zend_ast *name = zend_ast_create_zval_from_str(ZSTR_KNOWN(ZEND_STR_CLONE));
 			name->attr = ZEND_NAME_FQ;

Zend/zend_language_scanner.l

@@ -1613,6 +1613,11 @@ OPTIONAL_WHITESPACE_OR_COMMENTS ({WHITESPACE}|{MULTI_LINE_COMMENT}|{SINGLE_LINE_
 	RETURN_TOKEN_WITH_IDENT(T_NEW);
 }
 
+<ST_IN_SCRIPTING>"clone"{OPTIONAL_WHITESPACE_OR_COMMENTS}"(" {
+	yyless(5);
+	RETURN_TOKEN_WITH_STR(T_NAME_FULLY_QUALIFIED, 0);
+}
+
 <ST_IN_SCRIPTING>"clone" {
 	RETURN_TOKEN_WITH_IDENT(T_CLONE);
 }