MacroError type

src/error.rs

@@ -0,0 +1,32 @@
+use std::borrow::Cow;
+
+use proc_macro2::Span;
+use quote::quote_spanned;
+
+#[derive(Clone, Debug)]
+pub(crate) struct MacroError {
+    message: Cow<'static, str>,
+    span: Span,
+}
+
+impl MacroError {
+    pub(crate) fn new(message: Cow<'static, str>, span: Span) -> Self {
+        MacroError {
+            message,
+            span,
+        }
+    }
+
+    pub(crate) fn to_token_stream(&self) -> proc_macro::TokenStream {
+        self.to_token_stream2().into()
+    }
+
+    pub(crate) fn to_token_stream2(&self) -> proc_macro2::TokenStream {
+        let message = &self.message;
+        quote_spanned! {
+            self.span => ::std::compile_error!(#message);
+        }
+    }
+}
+
+pub(crate) type Result<T> = std::result::Result<T, MacroError>;