From 393a3e5e5e272e29e7bfd57fa2e8f986d3d11101 Mon Sep 17 00:00:00 2001
From: Stephen Gutekanst <stephen@hexops.com>
Date: Sun, 7 Apr 2024 13:54:46 -0700
Subject: [PATCH] module: add check for missing injected arguments

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
---
 src/module/module.zig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/module/module.zig b/src/module/module.zig
index a0551f6a..c40a1558 100644
--- a/src/module/module.zig
+++ b/src/module/module.zig
@@ -578,6 +578,12 @@ inline fn injectArgs(
                 continue :outer;
             }
         }
+        if (@typeInfo(arg.type) == .Pointer and @hasDecl(std.meta.Child(arg.type), "IsInjectedArgument")) {
+            // Argument is declared as injectable, but we do not have a value to inject for it.
+            // This can be the case if e.g. a Mod() parameter is specified, but that module is
+            // not registered.
+            @compileError("mach: cannot inject argument of type: " ++ @typeName(arg.type) ++ " - is it registered in your program's top-level `pub const modules = .{};`?");
+        }
 
         // First standard argument
         @field(args, arg.name) = std_args[std_args_index];