Elide ZEND_VERIFY_RETURN_TYPE when returning $this if possible

Zend/tests/return_types/025_2.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Return type of self is allowed in closure but $this return value must be checked as closure might not be bound to a class
+--FILE--
+<?php
+
+$c = function(): self { return $this; };
+try {
+	var_dump($c());
+} catch (Throwable $e) {
+	echo $e::class, ': ', $e->getMessage(), PHP_EOL;
+}
+?>
+--EXPECT--
+Error: Using $this when not in object context

Zend/zend_compile.c

@@ -2642,6 +2642,58 @@ static void zend_compile_memoized_expr(znode *result, zend_ast *expr, uint32_t t
 }
 /* }}} */
 
+static bool zend_is_this_instance_of_name(const zend_string *type_name)
+{
+	if (zend_string_equals_ci(CG(active_class_entry)->name, type_name)) {
+		return true;
+	}
+	if (zend_string_equals_ci(type_name, ZSTR_KNOWN(ZEND_STR_SELF))) {
+		return true;
+	}
+	if (zend_string_equals_ci(type_name, ZSTR_KNOWN(ZEND_STR_PARENT))) {
+		return true;
+	}
+
+	ZEND_ASSERT((CG(active_class_entry)->ce_flags & ZEND_ACC_LINKED) == 0);
+	if (CG(active_class_entry)->num_interfaces) {
+		for (uint32_t i = 0; i < CG(active_class_entry)->num_interfaces; i++) {
+			if (zend_string_equals_ci(CG(active_class_entry)->interface_names[i].lc_name, type_name)) {
+				return true;
+			}
+		}
+	}
+	const zend_string *parent_name = CG(active_class_entry)->parent_name;
+	if (parent_name && zend_string_equals_ci(parent_name, type_name)) {
+		return true;
+	}
+
+	return false;
+}
+
+static bool zend_is_this_valid_for_return_type(zend_type type)
+{
+	/* Closures can be bound to a class scope, however it might not and this must type error */
+	if (CG(active_op_array)->fn_flags & ZEND_ACC_CLOSURE) {
+		return false;
+	}
+
+	if (ZEND_TYPE_FULL_MASK(type) & (MAY_BE_OBJECT|MAY_BE_STATIC)) {
+		return true;
+	}
+
+	const zend_type *single_type;
+	ZEND_TYPE_FOREACH(type, single_type) {
+		if (ZEND_TYPE_HAS_NAME(*single_type)) {
+			const zend_string *name = ZEND_TYPE_NAME(*single_type);
+			if (zend_is_this_instance_of_name(name)) {
+				return true;
+			}
+		}
+	} ZEND_TYPE_FOREACH_END();
+
+	return false;
+}
+
 static void zend_emit_return_type_check(
 		znode *expr, const zend_arg_info *return_info, bool implicit) /* {{{ */
 {
@@ -2697,6 +2749,16 @@ static void zend_emit_return_type_check(
 			return;
 		}
 
+		/* If return type contains static and we are returning $this
+		 * (determined by checking if the previous opcode is ZEND_FETCH_THIS)
+		 * then we don't need to check the return type */
+		const zend_op_array *op_array = CG(active_op_array);
+		if (expr && op_array->last >= 1
+			&& op_array->opcodes[op_array->last-1].opcode == ZEND_FETCH_THIS
+			&& zend_is_this_valid_for_return_type(type)) {
+			return;
+		}
+
 		opline = zend_emit_op(NULL, ZEND_VERIFY_RETURN_TYPE, expr, NULL);
 		if (expr && expr->op_type == IS_CONST) {
 			opline->result_type = expr->op_type = IS_TMP_VAR;

ext/opcache/tests/opt/elide_self_verify_return_type_for_this.phpt

@@ -0,0 +1,100 @@
+--TEST--
+Return type check elision
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.optimization_level=-1
+opcache.opt_debug_level=0x20000
+opcache.preload=
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+
+class C1 {
+    public function foo(): self {
+        return $this;
+    }
+}
+
+class C2 {}
+class C3 extends C2 {
+    public function foo(): C3 {
+        return $this;
+    }
+}
+
+interface I1 {}
+
+class C4 implements I1 {
+    public function foo(): I1 {
+        return $this;
+    }
+}
+
+interface I2 extends I1 {}
+
+class C5 implements I2 {
+    public function foo(): I1 {
+        return $this;
+    }
+}
+
+class C6 extends C5 {
+    public function foo(): I2 {
+        return $this;
+    }
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=5, args=0, vars=0, tmps=0)
+     ; (after optimizer)
+     ; %s:1-39
+0000 DECLARE_CLASS string("c4")
+0001 DECLARE_CLASS string("i2")
+0002 DECLARE_CLASS string("c5")
+0003 DECLARE_CLASS_DELAYED string("c6") string("c5")
+0004 RETURN int(1)
+
+C1::foo:
+     ; (lines=2, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:4-6
+0000 T0 = FETCH_THIS
+0001 RETURN T0
+
+C3::foo:
+     ; (lines=2, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:11-13
+0000 T0 = FETCH_THIS
+0001 RETURN T0
+
+C4::foo:
+     ; (lines=2, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:19-21
+0000 T0 = FETCH_THIS
+0001 RETURN T0
+
+C5::foo:
+     ; (lines=3, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:27-29
+0000 T0 = FETCH_THIS
+0001 VERIFY_RETURN_TYPE T0
+0002 RETURN T0
+LIVE RANGES:
+     0: 0001 - 0002 (tmp/var)
+
+C6::foo:
+     ; (lines=3, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:33-35
+0000 T0 = FETCH_THIS
+0001 VERIFY_RETURN_TYPE T0
+0002 RETURN T0
+LIVE RANGES:
+     0: 0001 - 0002 (tmp/var)

ext/opcache/tests/opt/elide_static_verify_return_type_for_this.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Return type check elision
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.optimization_level=-1
+opcache.opt_debug_level=0x20000
+opcache.preload=
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+
+class C {
+    public function returnStatic(): static {
+        return $this;
+    }
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=1, args=0, vars=0, tmps=0)
+     ; (after optimizer)
+     ; %s:1-10
+0000 RETURN int(1)
+
+C::returnStatic:
+     ; (lines=2, args=0, vars=0, tmps=1)
+     ; (after optimizer)
+     ; %s:4-6
+0000 T0 = FETCH_THIS
+0001 RETURN T0