Partial function application (#20848)

RFC: https://wiki.php.net/rfc/partial_function_application_v2

Co-authored-by: Joe Watkins <krakjoe@php.net>

Author: arnaud-lb

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.6.0alpha3
 
+- Core:
+  . Implemented partial function application RFC. (Arnaud)
+
 - GMP:
   . Fixed GMP power and shift operators to reject GMP right operands outside
     the unsigned long range instead of silently truncating them. (Weilin Du)

UPGRADING

@@ -235,6 +235,8 @@ PHP 8.6 UPGRADE NOTES
     RFC: https://wiki.php.net/rfc/debugable-enums
   . #[\Override] can now be applied to class constants, including enum cases.
     RFC: https://wiki.php.net/rfc/override_constants
+  . Implemented partial function application
+    RFC: https://wiki.php.net/rfc/partial_function_application_v2
 
 - Curl:
   . curl_getinfo() return array now includes a new size_delivered key, which

UPGRADING.INTERNALS

@@ -132,6 +132,10 @@ PHP 8.6 INTERNALS UPGRADE NOTES
   . zend_argument_error_variadic() now takes a new 'function' parameters.
   . Added zend_argument_error_ex(), zend_argument_type_error_ex(),
     zend_argument_value_error_ex().
+  . Added zend_ast_dup().
+  . Added zend_compile_ast().
+  . Added zend_check_type_ex().
+  . Added zend_create_partial_closure().
 
 ========================
 2. Build system changes

Zend/Optimizer/compact_literals.c

@@ -733,6 +733,7 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 				case ZEND_SEND_VAR_NO_REF_EX:
 				case ZEND_SEND_REF:
 				case ZEND_SEND_FUNC_ARG:
+				case ZEND_SEND_PLACEHOLDER:
 				case ZEND_CHECK_FUNC_ARG:
 					if (opline->op2_type == IS_CONST) {
 						opline->result.num = cache_size;
@@ -745,6 +746,10 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 						cache_size += sizeof(void *);
 					}
 					break;
+				case ZEND_CALLABLE_CONVERT_PARTIAL:
+					opline->op1.num = cache_size;
+					cache_size += 2 * sizeof(void *);
+					break;
 			}
 			opline++;
 		}

Zend/Optimizer/optimize_func_calls.c

@@ -191,6 +191,7 @@ void zend_optimize_func_calls(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 			case ZEND_DO_UCALL:
 			case ZEND_DO_FCALL_BY_NAME:
 			case ZEND_CALLABLE_CONVERT:
+			case ZEND_CALLABLE_CONVERT_PARTIAL:
 				call--;
 				if (call_stack[call].func && call_stack[call].opline) {
 					zend_op *fcall = call_stack[call].opline;
@@ -223,13 +224,14 @@ void zend_optimize_func_calls(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 					 * At this point we also know whether or not the result of
 					 * the DO opcode is used, allowing to optimize calls to
 					 * ZEND_ACC_NODISCARD functions. */
-					if (opline->opcode != ZEND_CALLABLE_CONVERT) {
+					if (opline->opcode != ZEND_CALLABLE_CONVERT && opline->opcode != ZEND_CALLABLE_CONVERT_PARTIAL) {
 						opline->opcode = zend_get_call_op(fcall, call_stack[call].func, !RESULT_UNUSED(opline));
 					}
 
 					if ((ZEND_OPTIMIZER_PASS_16 & ctx->optimization_level)
 							&& call_stack[call].try_inline
-							&& opline->opcode != ZEND_CALLABLE_CONVERT) {
+							&& opline->opcode != ZEND_CALLABLE_CONVERT
+							&& opline->opcode != ZEND_CALLABLE_CONVERT_PARTIAL) {
 						zend_try_inline_call(op_array, fcall, opline, call_stack[call].func);
 					}
 				}

Zend/Optimizer/zend_call_graph.c

@@ -124,6 +124,7 @@ ZEND_API void zend_analyze_calls(zend_arena **arena, zend_script *script, uint32
 			case ZEND_DO_UCALL:
 			case ZEND_DO_FCALL_BY_NAME:
 			case ZEND_CALLABLE_CONVERT:
+			case ZEND_CALLABLE_CONVERT_PARTIAL:
 				func_info->flags |= ZEND_FUNC_HAS_CALLS;
 				if (call_info) {
 					call_info->caller_call_opline = opline;
@@ -140,6 +141,7 @@ ZEND_API void zend_analyze_calls(zend_arena **arena, zend_script *script, uint32
 			case ZEND_SEND_VAR_NO_REF:
 			case ZEND_SEND_VAR_NO_REF_EX:
 			case ZEND_SEND_USER:
+			case ZEND_SEND_PLACEHOLDER:
 				if (call_info) {
 					if (opline->op2_type == IS_CONST) {
 						call_info->named_args = true;

Zend/Optimizer/zend_inference.c

@@ -3903,6 +3903,7 @@ static zend_always_inline zend_result _zend_update_type_info(
 			}
 			break;
 		case ZEND_CALLABLE_CONVERT:
+		case ZEND_CALLABLE_CONVERT_PARTIAL:
 			UPDATE_SSA_TYPE(MAY_BE_OBJECT | MAY_BE_RC1 | MAY_BE_RCN, ssa_op->result_def);
 			UPDATE_SSA_OBJ_TYPE(zend_ce_closure, /* is_instanceof */ false, ssa_op->result_def);
 			break;

Zend/tests/first_class_callable/first_class_callable_non_unary_error.phpt

@@ -0,0 +1,45 @@
+--TEST--
+PFA of assert() behaves like a dynamic call to assert()
+--FILE--
+<?php
+
+try {
+    echo "# Static call:\n";
+    assert(false);
+} catch (Error $e) {
+    echo $e::class, ": ", $e->getMessage(), "\n";
+}
+
+try {
+    echo "# Dynamic call:\n";
+    (function ($f) { $f(false); })('assert');
+} catch (Error $e) {
+    echo $e::class, ": ", $e->getMessage() ?: '(no message)', "\n";
+}
+
+try {
+    echo "# PFA call:\n";
+    $f = assert(?);
+    $f(false);
+} catch (Error $e) {
+    echo $e::class, ": ", $e->getMessage() ?: '(no message)', "\n";
+}
+
+try {
+    echo "# Upper-case assert():\n";
+    $f = ASSERT(?);
+    $f(false);
+} catch (Error $e) {
+    echo $e::class, ": ", $e->getMessage() ?: '(no message)', "\n";
+}
+
+?>
+--EXPECT--
+# Static call:
+AssertionError: assert(false)
+# Dynamic call:
+AssertionError: (no message)
+# PFA call:
+AssertionError: (no message)
+# Upper-case assert():
+AssertionError: (no message)