merge(glittershark/achilles): Subtree import at 'b93268085a'

Imported from https://github.com/glittershark/achilles/

git-subtree-dir: users/glittershark/achilles
git-subtree-mainline: 4d193f2395
git-subtree-split: b93268085a
Change-Id: I64a583b454bbe03e20358ad7808939a4cbc212ba

users/glittershark/achilles/src/common/error.rs

@@ -0,0 +1,59 @@
+use std::{io, result};
+
+use thiserror::Error;
+
+use crate::{codegen, interpreter, parser, tc};
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    IOError(#[from] io::Error),
+
+    #[error("Error parsing input: {0}")]
+    ParseError(#[from] parser::Error),
+
+    #[error("Error evaluating expression: {0}")]
+    EvalError(#[from] interpreter::Error),
+
+    #[error("Compile error: {0}")]
+    CodegenError(#[from] codegen::Error),
+
+    #[error("Type error: {0}")]
+    TypeError(#[from] tc::Error),
+
+    #[error("{0}")]
+    Message(String),
+}
+
+impl From<String> for Error {
+    fn from(s: String) -> Self {
+        Self::Message(s)
+    }
+}
+
+impl<'a> From<&'a str> for Error {
+    fn from(s: &'a str) -> Self {
+        Self::Message(s.to_owned())
+    }
+}
+
+impl<'a> From<nom::Err<nom::error::Error<&'a str>>> for Error {
+    fn from(e: nom::Err<nom::error::Error<&'a str>>) -> Self {
+        use nom::error::Error as NomError;
+        use nom::Err::*;
+
+        Self::ParseError(match e {
+            Incomplete(i) => Incomplete(i),
+            Error(NomError { input, code }) => Error(NomError {
+                input: input.to_owned(),
+                code,
+            }),
+            Failure(NomError { input, code }) => Failure(NomError {
+                input: input.to_owned(),
+                code,
+            }),
+        })
+    }
+}
+
+pub type Result<T> = result::Result<T, Error>;