Implement short functions with auto capture

Zend/Optimizer/zend_cfg.h

@@ -99,6 +99,7 @@ typedef struct _zend_cfg {
 #define ZEND_CFG_RECV_ENTRY            (1<<24)
 #define ZEND_CALL_TREE                 (1<<23)
 #define ZEND_SSA_USE_CV_RESULTS        (1<<22)
+#define ZEND_DFG_SHORT_CLOSURE         (1<<21)
 
 #define CRT_CONSTANT_EX(op_array, opline, node) \
 	(((op_array)->fn_flags & ZEND_ACC_DONE_PASS_TWO) ? \

Zend/Optimizer/zend_dfg.c

@@ -25,18 +25,44 @@ static zend_always_inline void _zend_dfg_add_use_def_op(const zend_op_array *op_
 	const zend_op *next;
 
 	if (opline->op1_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
-		var_num = EX_VAR_TO_NUM(opline->op1.var);
-		if (!zend_bitset_in(def, var_num)) {
-			zend_bitset_incl(use, var_num);
+		if (build_flags & ZEND_DFG_SHORT_CLOSURE) {
+			switch (opline->opcode) {
+				case ZEND_ASSIGN:
+				case ZEND_ASSIGN_REF:
+				case ZEND_BIND_GLOBAL:
+				case ZEND_BIND_STATIC:
+				case ZEND_UNSET_CV:
+					break;
+				default:
+					var_num = EX_VAR_TO_NUM(opline->op1.var);
+					if (!zend_bitset_in(def, var_num)) {
+						zend_bitset_incl(use, var_num);
+					}
+					break;
+			}
+		} else {
+			var_num = EX_VAR_TO_NUM(opline->op1.var);
+			if (!zend_bitset_in(def, var_num)) {
+				zend_bitset_incl(use, var_num);
+			}
 		}
 	}
 	if (((opline->op2_type & (IS_VAR|IS_TMP_VAR)) != 0
 	  && opline->opcode != ZEND_FE_FETCH_R
 	  && opline->opcode != ZEND_FE_FETCH_RW)
 	 || (opline->op2_type == IS_CV)) {
-		var_num = EX_VAR_TO_NUM(opline->op2.var);
-		if (!zend_bitset_in(def, var_num)) {
-			zend_bitset_incl(use, var_num);
+		if (build_flags & ZEND_DFG_SHORT_CLOSURE) {
+			if (opline->opcode != ZEND_FE_FETCH_R && opline->opcode != ZEND_FE_FETCH_RW) {
+				var_num = EX_VAR_TO_NUM(opline->op2.var);
+				if (!zend_bitset_in(def, var_num)) {
+					zend_bitset_incl(use, var_num);
+				}
+			}
+		} else {
+			var_num = EX_VAR_TO_NUM(opline->op2.var);
+			if (!zend_bitset_in(def, var_num)) {
+				zend_bitset_incl(use, var_num);
+			}
 		}
 	}
 	if ((build_flags & ZEND_SSA_USE_CV_RESULTS)

Zend/tests/short_closures/001.phpt

@@ -0,0 +1,34 @@
+--TEST--
+Short closures
+--FILE--
+<?php
+
+$a = 1;
+$b = 2;
+
+$f = fn ($x) {
+    return [$a, $b, $x];
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "Result:\n";
+var_dump($f(3));
+--EXPECT--
+Captures:
+array(2) {
+  ["a"]=>
+  int(1)
+  ["b"]=>
+  int(2)
+}
+Result:
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  [2]=>
+  int(3)
+}

Zend/tests/short_closures/002.phpt

@@ -0,0 +1,77 @@
+--TEST--
+Short closures syntax variations
+--FILE--
+<?php
+
+$a = 1;
+
+function printFunctionSignature($f) {
+    $rf = new ReflectionFunction($f);
+    if ($rf->isStatic()) {
+        print 'static ';
+    }
+    print 'fn ';
+    if ($rf->returnsReference()) {
+        print '& ';
+    }
+    print '(...)';
+    $usedVars = $rf->getClosureUsedVariables();
+    if (count($usedVars) > 0) {
+        print ' use (';
+        $n = 0;
+        foreach ($usedVars as $var => $_) {
+            if ($n++ > 0) {
+                print ', ';
+            }
+            print $var;
+        }
+        print ')';
+    }
+    $type = $rf->getReturnType();
+    if ($type !== null) {
+        print ': ' . $type->getName();
+    }
+    print "\n";
+};
+
+$f = fn () {
+    return 1;
+};
+
+printFunctionSignature($f);
+
+$f = fn & () {
+    return 1;
+};
+
+printFunctionSignature($f);
+
+$f = static fn () {
+    return 1;
+};
+
+printFunctionSignature($f);
+
+$f = fn (): Foo {
+    return 1;
+};
+
+printFunctionSignature($f);
+
+$f = fn () use ($a) {
+};
+
+printFunctionSignature($f);
+
+$f = fn () use ($a): Foo {
+};
+
+printFunctionSignature($f);
+
+--EXPECTF--
+fn (...)
+fn & (...)
+static fn (...)
+fn (...): Foo
+fn (...) use (a)
+fn (...) use (a): Foo

Zend/tests/short_closures/explicit_use.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Short closures: explicit use
+--FILE--
+<?php
+
+$a = 1;
+$b = 2;
+
+$f = fn ($x) use ($a, &$b) {
+    $b = 4;
+    return [$a, $b, $x];
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "Result:\n";
+var_dump($f(3));
+
+echo "\$b:\n";
+var_dump($b);
+--EXPECT--
+Captures:
+array(2) {
+  ["a"]=>
+  int(1)
+  ["b"]=>
+  &int(2)
+}
+Result:
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(4)
+  [2]=>
+  int(3)
+}
+$b:
+int(4)

Zend/tests/short_closures/minimal_capture_001.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Short closures minimal capture: simple case
+--FILE--
+<?php
+
+$a = 1;
+$x = 1;
+
+$f = fn () {
+    $x = 2;
+    return $x + $a;
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f():\n";
+var_dump($f());
+--EXPECT--
+Captures:
+array(1) {
+  ["a"]=>
+  int(1)
+}
+f():
+int(3)

Zend/tests/short_closures/minimal_capture_002.phpt

@@ -0,0 +1,34 @@
+--TEST--
+Short closures minimal capture: loop
+--FILE--
+<?php
+
+$a = -1;
+$b = 2;
+
+// Captures $a because it may be used before definition
+$f = fn ($x) {
+    for ($i = 0; $i < $x; $i++) {
+        $a = $i;
+    }
+    return $a;
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f(3):\n";
+var_dump($f(3));
+
+echo "f(0):\n";
+var_dump($f(0));
+--EXPECT--
+Captures:
+array(1) {
+  ["a"]=>
+  int(-1)
+}
+f(3):
+int(2)
+f(0):
+int(-1)

Zend/tests/short_closures/minimal_capture_003.phpt

@@ -0,0 +1,38 @@
+--TEST--
+Short closures minimal capture: goto
+--FILE--
+<?php
+
+$a = -1;
+$b = 2;
+
+// Does not capture $a because it's always defined
+$f = fn ($x) {
+    goto end;
+
+    ret:
+    return $a + $x;
+
+    end:
+    $a = $b;
+    goto ret;
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f(3):\n";
+var_dump($f(3));
+
+echo "f(0):\n";
+var_dump($f(0));
+--EXPECT--
+Captures:
+array(1) {
+  ["b"]=>
+  int(2)
+}
+f(3):
+int(5)
+f(0):
+int(2)

Zend/tests/short_closures/minimal_capture_004.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Short closures minimal capture: static
+--FILE--
+<?php
+
+$a = 1;
+$x = 1;
+
+$f = fn () {
+    static $a;
+    $x = 2;
+    return $x + (int) $a;
+};
+
+echo "Captures or statics:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f():\n";
+var_dump($f(3));
+--EXPECT--
+Captures or statics:
+array(1) {
+  ["a"]=>
+  NULL
+}
+f():
+int(2)

Zend/tests/short_closures/minimal_capture_005.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Short closures minimal capture: assign ref
+--FILE--
+<?php
+
+$a = 1;
+$x = 1;
+
+$f = fn () {
+    $b = 2;
+    $x = &$b;
+    return $x + $a;
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f():\n";
+var_dump($f());
+--EXPECT--
+Captures:
+array(1) {
+  ["a"]=>
+  int(1)
+}
+f():
+int(3)

Zend/tests/short_closures/minimal_capture_006.phpt

@@ -0,0 +1,23 @@
+--TEST--
+Short closures minimal capture: global
+--FILE--
+<?php
+
+$a = 1;
+
+$f = fn () {
+    global $a;
+    return $a;
+};
+
+echo "Captures:\n";
+var_dump((new ReflectionFunction($f))->getStaticVariables());
+
+echo "f():\n";
+var_dump($f());
+--EXPECT--
+Captures:
+array(0) {
+}
+f():
+int(1)