Rust: skeleton trap file emission code

rust/src/main.rs

@@ -8,7 +8,7 @@ use ra_ap_load_cargo::{load_workspace_at, LoadCargoConfig, ProcMacroServerChoice
 
 
 mod config;
-
+mod trap;
 
 fn main() -> anyhow::Result<()> {
     let cfg = config::Config::extract().context("failed to load configuration")?;

rust/src/trap.rs

@@ -0,0 +1,53 @@
+use std::fmt::Formatter;
+use std::fs::File;
+use std::io::Write;
+use std::path::{PathBuf};
+
+#[derive(Debug)]
+struct TrapLabel(u64);
+
+impl std::fmt::Display for TrapLabel {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "#{:x}", self.0)
+    }
+}
+
+trait TrapEntry: std::fmt::Display {}
+
+#[derive(Debug)]
+struct TrapFile {
+    label_index: u64,
+    file: File,
+}
+
+impl TrapFile {
+    pub fn new(path: &PathBuf) -> std::io::Result<TrapFile> {
+        let file = File::create(path)?;
+        Ok(TrapFile {
+            label_index: 0,
+            file: file,
+        })
+    }
+
+    pub fn insert_comment(&mut self, comment: &str) -> std::io::Result<()> {
+        write!(self.file, "/* {comment} */\n")
+    }
+
+    pub fn allocate_label(&mut self) -> std::io::Result<TrapLabel> {
+        let ret = TrapLabel(self.label_index);
+        write!(self.file, "{ret}=*\n")?;
+        self.label_index += 1;
+        Ok(ret)
+    }
+
+    pub fn allocate_label_for(&mut self, key: &str) -> std::io::Result<TrapLabel> {
+        let ret = TrapLabel(self.label_index);
+        write!(self.file, "{ret}=\"{}\"\n", key.replace("\"", "\"\""))?;
+        self.label_index += 1;
+        Ok(ret)
+    }
+
+    pub fn emit<T: TrapEntry>(&mut self, entry: T) -> std::io::Result<()> {
+        write!(self.file, "{entry}\n")
+    }
+}