Support every argument syntax for clone()

[TimWolla]

Follow-up for #18919 and extracted out of #18747.

[nielsdos]

Right... shift-reduce conflict on argument vs expression...
I'll have a better look tomorrow or so, but on first sight this seems fine. I wonder if it's possible to make it even simpler, but this is already quite simple.

[nielsdos]

It seems right to me. Please add a comment to the parser to explain that the reason you do this is to resolve a shift-reduce conflict.

[iluuu1994]

Looks correct. As mentioned, this could also have been solved with lexer lookahead, which would have been simpler. But I understand why people don't like these solutions as much. 😋

[iluuu1994]

A few minutes too late, I had the idea that we could just treat clone as an identifier rather than a keyword when it's followed by (. This way, clone ($foo) is just treated as a function call, which solves the problem automatically, while also not requiring any new special tokens. Something like:

diff --git a/Zend/zend_language_parser.y b/Zend/zend_language_parser.y
index 805f378cb98..c92e830b8f1 100644
--- a/Zend/zend_language_parser.y
+++ b/Zend/zend_language_parser.y
@@ -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
@@ -914,31 +914,6 @@ 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
-			{ $$ = zend_ast_list_add($1, $3); }
-;
-
 argument_no_expr:
 		identifier ':' expr
 			{ $$ = zend_ast_create(ZEND_AST_NAMED_ARG, $1, $3); }
@@ -1257,11 +1232,6 @@ 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;
diff --git a/Zend/zend_language_scanner.l b/Zend/zend_language_scanner.l
index 5e377249422..d3917c4dc89 100644
--- a/Zend/zend_language_scanner.l
+++ b/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);
 }

WDYT?