aster 0.37.0

A libsyntax ast builder
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use syntax::ast;
use syntax::codemap::{self, DUMMY_SP, Span, respan};
use syntax::ext::base::{DummyResolver, ExtCtxt};
use syntax::ext::expand;
use syntax::ext::quote::rt::ToTokens;
use syntax::parse::ParseSess;
use syntax::ptr::P;
use syntax::tokenstream::TokenTree;

use expr::ExprBuilder;
use invoke::{Invoke, Identity};
use path::PathBuilder;
use symbol::ToSymbol;

/// A Builder for macro invocations.
///
/// Note that there are no commas added between args, as otherwise
/// that macro invocations that could be expressed would be limited.
/// You will need to add all required symbols with `with_arg` or
/// `with_argss`.
pub struct MacBuilder<F=Identity> {
    callback: F,
    span: Span,
}

impl MacBuilder {
    pub fn new() -> Self {
        MacBuilder::with_callback(Identity)
    }
}

impl<F> MacBuilder<F>
    where F: Invoke<ast::Mac>
{
    pub fn with_callback(callback: F) -> Self {
        MacBuilder {
            callback: callback,
            span: DUMMY_SP,
        }
    }

    pub fn span(mut self, span: Span) -> Self {
        self.span = span;
        self
    }

    pub fn build_path(self, path: ast::Path) -> MacPathBuilder<F> {
        MacPathBuilder {
            callback: self.callback,
            span: self.span,
            path: path,
            tokens: vec![],
        }
    }

    pub fn path(self) -> PathBuilder<Self> {
        let span = self.span;
        PathBuilder::with_callback(self).span(span)
    }
}

impl<F> Invoke<ast::Path> for MacBuilder<F>
    where F: Invoke<ast::Mac>,
{
    type Result = MacPathBuilder<F>;

    fn invoke(self, path: ast::Path) -> Self::Result {
        self.build_path(path)
    }
}

//////////////////////////////////////////////////////////////////////////////

pub struct MacPathBuilder<F> {
    callback: F,
    span: Span,
    path: ast::Path,
    tokens: Vec<TokenTree>,
}

impl<F> MacPathBuilder<F>
    where F: Invoke<ast::Mac>,
{
    pub fn with_args<I, T>(self, iter: I) -> Self
        where I: IntoIterator<Item=T>, T: ToTokens
    {
        iter.into_iter().fold(self, |self_, expr| self_.with_arg(expr))
    }

    pub fn with_arg<T>(mut self, expr: T) -> Self
        where T: ToTokens
    {
        let parse_sess = ParseSess::new();
        let mut macro_loader = DummyResolver;
        let cx = make_ext_ctxt(&parse_sess, &mut macro_loader);
        let tokens = expr.to_tokens(&cx);
        assert!(tokens.len() == 1);
        self.tokens.push(tokens[0].clone());
        self
    }

    pub fn expr(self) -> ExprBuilder<Self> {
        let span = self.span;
        ExprBuilder::with_callback(self).span(span)
    }

    pub fn build(self) -> F::Result {
        let mac = ast::Mac_ {
            path: self.path,
            tts: self.tokens,
        };
        self.callback.invoke(respan(self.span, mac))
    }
}

impl<F> Invoke<P<ast::Expr>> for MacPathBuilder<F>
    where F: Invoke<ast::Mac>,
{
    type Result = Self;

    fn invoke(self, expr: P<ast::Expr>) -> Self {
        self.with_arg(expr)
    }
}

//////////////////////////////////////////////////////////////////////////////

fn make_ext_ctxt<'a>(sess: &'a ParseSess,
                     macro_loader: &'a mut DummyResolver) -> ExtCtxt<'a> {
    let info = codemap::ExpnInfo {
        call_site: codemap::DUMMY_SP,
        callee: codemap::NameAndSpan {
            format: codemap::MacroAttribute("test".to_symbol()),
            allow_internal_unstable: false,
            span: None
        }
    };

    let ecfg = expand::ExpansionConfig::default(String::new());
    let mut cx = ExtCtxt::new(sess, ecfg, macro_loader);
    cx.bt_push(info);

    cx
}