Always memoize calls in lhs of coalesce assignment

We don't want to invoke calls twice, even if they are considered "variables",
i.e. might be writable if returning a reference. Function calls behave the same
in all BP contexts so they don't need to be invoked twice. The singular
exception to this is nullsafe coalesce in isset/empty, because it needs to
return false/true respectively when short-circuited. However, since nullsafe
calls are not allwed in write context we may ignore this problem.

Author: iluuu1994

Zend/tests/assign_coalesce_008.phpt

@@ -0,0 +1,64 @@
+--TEST--
+Assign coalesce: All calls should be memoized
+--FILE--
+<?php
+class Foo {
+    public $prop;
+
+    public function foo() {
+        echo __METHOD__, "\n";
+        return $this;
+    }
+
+    public function bar() {
+        echo __METHOD__, "\n";
+        return 'prop';
+    }
+
+    public function __isset($name) {
+        echo __METHOD__, "\n";
+        return false;
+    }
+
+    public function __set($name, $value) {
+        echo __METHOD__, "\n";
+        var_dump($value);
+    }
+}
+
+function &foo() {
+    global $foo;
+    echo __FUNCTION__, "\n";
+    return $foo;
+}
+function bar() {
+    echo __FUNCTION__, "\n";
+}
+
+foo(bar())['bar'] ??= 42;
+var_dump($foo);
+
+$foo = new Foo();
+$foo->foo()->foo()->{$foo->bar()} ??= 42;
+var_dump($foo);
+$foo->foo()->baz ??= 42;
+
+?>
+--EXPECT--
+bar
+foo
+array(1) {
+  ["bar"]=>
+  int(42)
+}
+Foo::foo
+Foo::foo
+Foo::bar
+object(Foo)#1 (1) {
+  ["prop"]=>
+  int(42)
+}
+Foo::foo
+Foo::__isset
+Foo::__set
+int(42)

Zend/zend_compile.c

@@ -10558,6 +10558,17 @@ static zend_op *zend_compile_var_inner(znode *result, zend_ast *ast, uint32_t ty
 {
 	CG(zend_lineno) = zend_ast_get_lineno(ast);
 
+	if (CG(memoize_mode) != ZEND_MEMOIZE_NONE) {
+		switch (ast->kind) {
+			case ZEND_AST_CALL:
+			case ZEND_AST_METHOD_CALL:
+			case ZEND_AST_NULLSAFE_METHOD_CALL:
+			case ZEND_AST_STATIC_CALL:
+				zend_compile_memoized_expr(result, ast);
+				return &CG(active_op_array)->opcodes[CG(active_op_array)->last - 1];
+		}
+	}
+
 	switch (ast->kind) {
 		case ZEND_AST_VAR:
 			return zend_compile_simple_var(result, ast, type, 0);