assembler: enhance error handling and tokenization logic

assembler/src/source/token_info.rs

@@ -21,14 +21,14 @@ pub struct RegisterToken {
 }
 
 impl RegisterToken {
+    #[must_use]
+    pub const fn new(reg: Register) -> Self {
+        Self { reg }
+    }
+
     /// Returns the name of a valid [`Register`]
     #[must_use]
     pub fn name(&self) -> String {
         self.reg.to_string()
     }
 }
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct InstructionToken {
-    pub mnemonic: String,
-}