Fix lack of location for reporting lambdas with missing return statement #1857.

test/test_suite/functions/missing_return_lambda.c3

@@ -0,0 +1,9 @@
+import std::io::path;
+
+fn void! process_dir(String dir_name)
+{
+	path::Path p = path::temp_new(dir_name)!;
+	path::PathWalker fnwalk = fn bool!(Path p, bool is_dir, void*) { // #error: issing return statement at the end
+		io::printfn("path is %s", p);
+    };
+}