Fix docs appearance at cargo.io and docs.rs
diff --git a/Cargo.toml b/Cargo.toml
index b0c318f..1a17078 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
[package]
name = "proc-macro-error"
-version = "0.1.1"
+version = "0.1.2"
authors = ["CreepySkeleton <creepy-skeleton@yandex.ru>"]
description = "Drop-in replacement to panics in proc-macros"
diff --git a/src/lib.rs b/src/lib.rs
index e3a64e2..362b6e2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,105 @@
+//! Drop-in replacement to panics in proc-macros.
+//!
+//! # Motivation
+//!
+//! Error handling in proc-macros sucks. It's not much of a choice today:
+//! you either "bubble up" the error up to top-level of you macro and convert it to
+//! a [`compile_error!`][compl_err] invocation or just use a good old panic. Both these ways suck:
+//!
+//! - Former sucks because it's quite redundant to unroll a proper error handling
+//! just for critical errors that will crash the macro anyway so people mostly
+//! choose not to bother with it at all and use panic. I have yet to see a crate > 700
+//! lines of code that does it, simple `.expect` is too tempting.
+//! - Later sucks because there's no way to carry out span info via panic. `rustc` will highlight
+//! the whole invocation itself but not some specific token inside it.
+//! Furthermore, panics aren't for error-reporting at all; panics are for bug-detecting
+//! (like unwrapping on `None` or out-of range indexing) or for early development stages
+//! when you need a prototype ASAP and error handling can wait. Mixing these usages only
+//! messes things up.
+//!
+//! # Solution
+//!
+//! That said, we need a solution, but this solution must meet these conditions:
+//!
+//! - It must be better than panics. The main point: it must offer a way to carry span information
+//! over to user.
+//! - It must require as little effort as possible to migrate from panic. Ideally, a new
+//! macro with the same semantics plus ability to carry out span info.
+//!
+//! This crate aims to provide such a mechanism. All you have to do is enclose all
+//! the code inside your top-level `#[proc_macro]` function in [`filter_macro_errors!`]
+//! invocation and change panics to [`span_error!`]/[`call_site_error!`] where appropriate:
+//!
+//! ```rust, ignore
+//! // This is your main entry point
+//! #[proc_macro]
+//! pub fn make_answer(input: TokenStream) -> TokenStream {
+//! // This macro **must** be placed at the top level.
+//! // No need to touch the code inside though.
+//! filter_macro_errors! {
+//! // `parse_macro_input!` and friends work just fine inside this macro
+//! let input = parse_macro_input!(input as MyParser);
+//!
+//! if let Err(err) = some_logic(&input) {
+//! // we've got a span to blame, let's use it
+//! let span = err.span_should_be_highlighted();
+//! let msg = err.message();
+//! // This call jumps directly to the end of `filter_macro_errors!` invocation
+//! span_error!(span, "You made an error, go fix it: {}", msg);
+//! }
+//!
+//! // `Result` gets some handy shortcuts if your error type implements
+//! // `Into<``MacroError``>`. `Option` has some unconditionally
+//! use proc_macro_error::ResultExt;
+//! more_logic(&input).expect_or_exit("What a careless user, behave!");
+//!
+//! if !more_logic_for_logic_god!(&input) {
+//! // We don't have an exact location this time,
+//! // so just highlight the proc-macro invocation itself
+//! call_site_error!(
+//! "Bad, bad user! Now go stand in the corner and think about what you did!");
+//! }
+//!
+//! // Now all the processing is done, return `proc_macro::TokenStream`
+//! quote!(/* stuff */).into()
+//! }
+//!
+//! // At this point we have a new shining `proc_macro::TokenStream`!
+//! }
+//! ```
+//!
+//! # How it works
+//! I must confess: I used panics as a try/catch mechanism. I've committed this
+//! sin so others may live in peace and prosperity, god save my soul.
+//!
+//! Essentially, the [`filter_macro_errors!`] macro is a
+//! ```C++
+//! try {
+//! /* your code */
+//! } catch (MacroError) {
+//! /* conversion to compile_error! */
+//! }
+//! ```
+//!
+//! [`span_error!`] and co are
+//! ```C++
+//! throw MacroError::new(span, format!(msg...));
+//! ```
+//!
+//! By calling [`span_error!`] you trigger panic
+//! that will be caught by [`filter_macro_errors!`] and converted to [`compile_error!`][compl_err] invocation.
+//! All the panics that wasn't triggered by [`span_error!`] and co but any other reason will be resumed as is.
+//!
+//! Panic catching is indeed *slow* but the macro is about to abort anyway so speed is not
+//! a concern here. Please note that this crate is not intended to be used in any other way
+//! than a proc-macro error reporting, use [`Result`] and `?` instead.
+//!
+//! # Testing
+//! TODO: fork https://github.com/laumann/compiletest-rs and make it understand explicit line numbers.
+//!
+//! [compl_err]: https://doc.rust-lang.org/std/macro.compile_error.html
+//!
+
// reexports for use in macros
pub extern crate proc_macro;
pub extern crate proc_macro2;
