add better panic message and restructure src/args.rs

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

src/main.rs

@@ -1,6 +1,28 @@
-use tricc::args;
+use std::fs;
+use std::panic;
+
+use tricc::args::Args;
 
 fn main() {
-    let file: String = args::handle();
-    println!("{}", file);
+    panic::set_hook(Box::new(|panic_info| {
+        if let Some(msg) = panic_info.payload().downcast_ref::<&str>() {
+            eprintln!("{}", msg);
+        } else if let Some(msg) = panic_info.payload().downcast_ref::<String>() {
+            eprintln!("{}", msg);
+        } else if let Some(location) = panic_info.location() {
+            eprintln!(
+                "panic occurred in file '{}' at line {}",
+                location.file(),
+                location.line(),
+            );
+        } else {
+            eprintln!("panic occurred");
+        }
+    }));
+
+    let mut args = Args::new();
+    args.handle();
+
+    let file = args.get_file();
+    let contents = fs::read_to_string(&file).expect("Couldn't read the file");
 }