Refactor logos-derive from tree to graph

Cargo.toml

@@ -8,3 +8,6 @@ members = [
 [profile]
 release = { lto = true }
 bench = { lto = true }
+
+[patch.crates-io]
+logos-derive = { path = "./logos-derive" }

logos-derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "logos-derive"
-version = "0.10.0-rc2"
+version = "0.10.0-rc3"
 authors = ["maciejhirsz <maciej.hirsz@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Create ridiculously fast Lexers"
@@ -16,9 +16,14 @@ name = "logos_derive"
 proc-macro = true
 
 [dependencies]
+beef = "0.4.1"
+fnv = "1.0.6"
 rustc-hash = "1.0.1"
-syn = { version = "0.15", features = ["extra-traits", "full"] }
-quote = "0.6"
-proc-macro2 = "0.4"
+syn = { version = "1.0.17", features = ["extra-traits", "full"] }
+quote = "1.0.3"
+proc-macro2 = "1.0.9"
 regex-syntax = "0.6"
 utf8-ranges = "1.0"
+
+[dev-dependencies]
+pretty_assertions = "0.6.1"

logos-derive/src/error.rs

@@ -0,0 +1,73 @@
+use std::fmt;
+
+use beef::lean::Cow;
+use proc_macro2::{Span, TokenStream};
+use quote::{quote_spanned, ToTokens, TokenStreamExt};
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+pub struct Error(Cow<'static, str>);
+
+#[derive(Debug)]
+pub struct SpannedError {
+    message: Cow<'static, str>,
+    span: Span,
+}
+
+impl Error {
+    pub fn new<M>(message: M) -> Self
+    where
+        M: Into<Cow<'static, str>>,
+    {
+        Error(message.into())
+    }
+
+    pub fn span(self, span: Span) -> SpannedError {
+        SpannedError {
+            message: self.0,
+            span,
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl From<regex_syntax::Error> for Error {
+    fn from(err: regex_syntax::Error) -> Error {
+        Error(err.to_string().into())
+    }
+}
+
+impl From<&'static str> for Error {
+    fn from(err: &'static str) -> Error {
+        Error(err.into())
+    }
+}
+
+impl From<String> for Error {
+    fn from(err: String) -> Error {
+        Error(err.into())
+    }
+}
+
+impl ToTokens for SpannedError {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let message = &*self.message;
+
+        tokens.append_all(
+            quote_spanned!(self.span => {
+                compile_error!(#message)
+            })
+        )
+    }
+}