From 61c51f0ac96f91254c6acc6c23b8d09f38b49480 Mon Sep 17 00:00:00 2001
From: g-w1 <58830309+g-w1@users.noreply.github.com>
Date: Wed, 11 Nov 2020 08:54:08 -0500
Subject: [PATCH] Add error for missing positional arguments in zig build-*

Closes #6938
---
 src/main.zig | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 0520724f73..1a838f1755 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1267,9 +1267,17 @@ fn buildOutputType(
     }
 
     if (link_objects.items.len == 0 and root_src_file == null and
-        c_source_files.items.len == 0 and arg_mode == .run)
+        c_source_files.items.len == 0 and !show_builtin)
     {
-        fatal("`zig run` expects at least one positional argument", .{});
+        switch (arg_mode) {
+            .run => fatal("`zig run` expects at least one positional argument", .{}),
+            .build => |build_type| switch (build_type) {
+                .Exe => fatal("`zig build-exe` expects at least one positional argument", .{}),
+                .Lib => fatal("`zig build-lib` expects at least one positional argument", .{}),
+                .Obj => fatal("`zig build-obj` expects at least one positional argument", .{}),
+            },
+            else => {},
+        }
     }
 
     const root_name = if (provided_name) |n| n else blk: {