Improve "already declared" error message

If this error is missing because the rtd_key was renamed to lcname,
fetch the class based on lcname and use the class type and cased
name from there.

Author: nikic

Zend/tests/declare_already_in_use.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Cannot declare class, because the name is already in use
+--FILE--
+<?php
+
+function test() {
+    class A {}
+}
+test();
+test();
+
+?>
+--EXPECTF--
+Fatal error: Cannot declare class A, because the name is already in use in %s on line %d

Zend/zend_compile.c

@@ -1067,12 +1067,9 @@ ZEND_API int do_bind_class(zval *lcname, zend_string *lc_parent_name) /* {{{ */
 	zv = zend_hash_find_ex(EG(class_table), Z_STR_P(rtd_key), 1);
 
 	if (UNEXPECTED(!zv)) {
-		/* If we're in compile time, in practice, it's quite possible
-		 * that we'll never reach this class declaration at runtime,
-		 * so we shut up about it.  This allows the if (!defined('FOO')) { return; }
-		 * approach to work.
-		 */
-		zend_error_noreturn(E_COMPILE_ERROR, "Cannot declare  %s, because the name is already in use", Z_STRVAL_P(lcname));
+		ce = zend_hash_find_ptr(EG(class_table), Z_STR_P(lcname));
+		ZEND_ASSERT(ce && "Class with lcname should be registered");
+		zend_error_noreturn(E_COMPILE_ERROR, "Cannot declare %s %s, because the name is already in use", zend_get_object_type(ce), ZSTR_VAL(ce->name));
 		return FAILURE;
 	}