checker: check option and result handling in as casts (#17133)

vlib/v/checker/checker.v

@@ -1052,6 +1052,8 @@ fn (mut c Checker) check_expr_opt_call(expr ast.Expr, ret_type ast.Type) ast.Typ
 		}
 	} else if expr is ast.CastExpr {
 		c.check_expr_opt_call(expr.expr, ret_type)
+	} else if expr is ast.AsCast {
+		c.check_expr_opt_call(expr.expr, ret_type)
 	}
 	return ret_type
 }
@@ -1088,7 +1090,6 @@ fn (mut c Checker) check_or_expr(node ast.OrExpr, ret_type ast.Type, expr_return
 		}
 		return
 	}
-
 	if node.stmts.len == 0 {
 		if ret_type != ast.void_type {
 			// x := f() or {}
@@ -1176,7 +1177,7 @@ fn (mut c Checker) check_or_last_stmt(stmt ast.Stmt, ret_type ast.Type, expr_ret
 				}
 			}
 			else {
-				if stmt.typ == ast.void_type {
+				if stmt.typ == ast.void_type || expr_return_type == ast.void_type {
 					return
 				}
 				if is_noreturn_callexpr(stmt.expr) {

vlib/v/checker/tests/as_cast_option_result_unhandled_err.out

@@ -0,0 +1,11 @@
+vlib/v/checker/tests/as_cast_option_result_unhandled_err.vv:11:6: error: ret_sum_result() returns a result, so it should have either an `or {}` block, or `!` at the end
+    9 | }
+   10 |
+   11 | _ := ret_sum_result() as int
+      |      ~~~~~~~~~~~~~~~~
+   12 | _ := ret_sum_option() as string
+vlib/v/checker/tests/as_cast_option_result_unhandled_err.vv:12:6: error: ret_sum_option() returns an option, so it should have either an `or {}` block, or `?` at the end
+   10 |
+   11 | _ := ret_sum_result() as int
+   12 | _ := ret_sum_option() as string
+      |      ~~~~~~~~~~~~~~~~

vlib/v/checker/tests/as_cast_option_result_unhandled_err.vv

@@ -0,0 +1,12 @@
+type Sum = int | string
+
+fn ret_sum_result() !Sum {
+	return 0
+}
+
+fn ret_sum_option() ?Sum {
+	return '0'
+}
+
+_ := ret_sum_result() as int
+_ := ret_sum_option() as string

vlib/v/eval/eval.v

@@ -45,7 +45,7 @@ pub struct EvalTrace {
 pub fn (mut e Eval) eval(mut files []&ast.File) {
 	e.register_symbols(mut files)
 	// println(files.map(it.path_base))
-	e.run_func(e.mods['main']['main'] or { ast.EmptyStmt{} } as ast.FnDecl)
+	e.run_func(e.mods['main']['main'] or { ast.FnDecl{} } as ast.FnDecl)
 }
 
 // first arg is reciever (if method)