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use errors::DiagnosticBuilder;
use syntax::ast::{self, *};
use syntax::source_map::Spanned;
use syntax::ext::base::*;
use syntax::ext::build::AstBuilder;
use syntax::parse::token;
use syntax::print::pprust;
use syntax::ptr::P;
use syntax::symbol::Symbol;
use syntax::tokenstream::{TokenStream, TokenTree};
use syntax_pos::{Span, DUMMY_SP};
pub fn expand_assert<'cx>(
cx: &'cx mut ExtCtxt,
sp: Span,
tts: &[TokenTree],
) -> Box<dyn MacResult + 'cx> {
let Assert { cond_expr, custom_message } = match parse_assert(cx, sp, tts) {
Ok(assert) => assert,
Err(mut err) => {
err.emit();
return DummyResult::expr(sp);
}
};
let sp = sp.apply_mark(cx.current_expansion.mark);
let panic_call = Mac_ {
path: Path::from_ident(Ident::new(Symbol::intern("panic"), sp)),
tts: custom_message.unwrap_or_else(|| {
TokenStream::from(TokenTree::Token(
DUMMY_SP,
token::Literal(
token::Lit::Str_(Name::intern(&format!(
"assertion failed: {}",
pprust::expr_to_string(&cond_expr).escape_debug()
))),
None,
),
))
}).into(),
delim: MacDelimiter::Parenthesis,
};
let if_expr = cx.expr_if(
sp,
cx.expr(sp, ExprKind::Unary(UnOp::Not, cond_expr)),
cx.expr(
sp,
ExprKind::Mac(Spanned {
span: sp,
node: panic_call,
}),
),
None,
);
MacEager::expr(if_expr)
}
struct Assert {
cond_expr: P<ast::Expr>,
custom_message: Option<TokenStream>,
}
fn parse_assert<'a>(
cx: &mut ExtCtxt<'a>,
sp: Span,
tts: &[TokenTree]
) -> Result<Assert, DiagnosticBuilder<'a>> {
let mut parser = cx.new_parser_from_tts(tts);
if parser.token == token::Eof {
let mut err = cx.struct_span_err(sp, "macro requires a boolean expression as an argument");
err.span_label(sp, "boolean expression required");
return Err(err);
}
Ok(Assert {
cond_expr: parser.parse_expr()?,
custom_message: if parser.eat(&token::Comma) {
let ts = parser.parse_tokens();
if !ts.is_empty() {
Some(ts)
} else {
None
}
} else {
None
},
})
}
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