Forbid "return;" for typed returns already at compile-time

These would otherwise generate a "none returned" error at runtime.
Catch them early.

Author: nikic

Zend/tests/return_types/029.phpt

@@ -9,7 +9,7 @@ function foo() : array {
 	try {
 		throw new Exception("xxxx");
 	} finally {
-		return ;
+		return null;
 	}
 }
 
@@ -21,7 +21,7 @@ Stack trace:
 #0 %s(%d): foo()
 #1 {main}
 
-Next TypeError: Return value of foo() must be of the type array, none returned in %s29.php:%d
+Next TypeError: Return value of foo() must be of the type array, null returned in %s29.php:%d
 Stack trace:
 #0 %s(%d): foo()
 #1 {main}

Zend/tests/return_types/bug71092.phpt

@@ -9,14 +9,14 @@ function boom(): array {
 	$data = [['id']];
 	switch ($data[0]) {
 	case ['id']:
-		return;
+		return null;
 	}
 }
 
 boom();
 ?>
 --EXPECTF--
-Fatal error: Uncaught TypeError: Return value of boom() must be of the type array, none returned in %sbug71092.php:%d
+Fatal error: Uncaught TypeError: Return value of boom() must be of the type array, null returned in %sbug71092.php:%d
 Stack trace:
 #0 %s(%d): boom()
 #1 {main}

Zend/tests/type_declarations/typed_return_without_value.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Typed return without value generates compile-time error
+--FILE--
+<?php
+
+function test() : int {
+    return;
+}
+
+test();
+
+?>
+--EXPECTF--
+Fatal error: A function with return type must return a value in %s on line %d

Zend/zend_compile.c

@@ -2264,7 +2264,8 @@ static zend_op *zend_delayed_compile_end(uint32_t offset) /* {{{ */
 }
 /* }}} */
 
-static void zend_emit_return_type_check(znode *expr, zend_arg_info *return_info) /* {{{ */
+static void zend_emit_return_type_check(
+		znode *expr, zend_arg_info *return_info, zend_bool implicit) /* {{{ */
 {
 	/* `return ...;` is illegal in a void function (but `return;` isn't) */
 	if (return_info->type_hint == IS_VOID) {
@@ -2278,6 +2279,11 @@ static void zend_emit_return_type_check(znode *expr, zend_arg_info *return_info)
 	if (return_info->type_hint != IS_UNDEF) {
 		zend_op *opline;
 
+		if (!expr && !implicit) {
+			zend_error_noreturn(E_COMPILE_ERROR,
+				"A function with return type must return a value");
+		}
+
 		if (expr && expr->op_type == IS_CONST) {
 			if ((return_info->type_hint == Z_TYPE(expr->u.constant))
 			 ||((return_info->type_hint == _IS_BOOL)
@@ -2312,7 +2318,7 @@ void zend_emit_final_return(int return_one) /* {{{ */
 	zend_bool returns_reference = (CG(active_op_array)->fn_flags & ZEND_ACC_RETURN_REFERENCE) != 0;
 
 	if (CG(active_op_array)->fn_flags & ZEND_ACC_HAS_RETURN_TYPE) {
-		zend_emit_return_type_check(NULL, CG(active_op_array)->arg_info - 1);
+		zend_emit_return_type_check(NULL, CG(active_op_array)->arg_info - 1, 1);
 	}
 
 	zn.op_type = IS_CONST;
@@ -4058,7 +4064,8 @@ void zend_compile_return(zend_ast *ast) /* {{{ */
 
 	/* Generator return types are handled separately */
 	if (!(CG(active_op_array)->fn_flags & ZEND_ACC_GENERATOR) && CG(active_op_array)->fn_flags & ZEND_ACC_HAS_RETURN_TYPE) {
-		zend_emit_return_type_check(expr_ast ? &expr_node : NULL, CG(active_op_array)->arg_info - 1);
+		zend_emit_return_type_check(
+			expr_ast ? &expr_node : NULL, CG(active_op_array)->arg_info - 1, 0);
 	}
 
 	zend_handle_loops_and_finally();