mv compiler to compiler/

compiler/rustc_errors/src/registry.rs

@@ -0,0 +1,29 @@
+use rustc_data_structures::fx::FxHashMap;
+
+#[derive(Debug)]
+pub struct InvalidErrorCode;
+
+#[derive(Clone)]
+pub struct Registry {
+    long_descriptions: FxHashMap<&'static str, Option<&'static str>>,
+}
+
+impl Registry {
+    pub fn new(long_descriptions: &[(&'static str, Option<&'static str>)]) -> Registry {
+        Registry { long_descriptions: long_descriptions.iter().copied().collect() }
+    }
+
+    /// This will panic if an invalid error code is passed in
+    pub fn find_description(&self, code: &str) -> Option<&'static str> {
+        self.long_descriptions[code]
+    }
+    /// Returns `InvalidErrorCode` if the code requested does not exist in the
+    /// registry. Otherwise, returns an `Option` where `None` means the error
+    /// code is valid but has no extended information.
+    pub fn try_find_description(
+        &self,
+        code: &str,
+    ) -> Result<Option<&'static str>, InvalidErrorCode> {
+        self.long_descriptions.get(code).copied().ok_or(InvalidErrorCode)
+    }
+}