From ff95ba3a8c1cc2cf9b1901a18ba73434f3380c0d Mon Sep 17 00:00:00 2001 From: Aravind Gollakota Date: Tue, 5 Jul 2016 21:35:12 -0700 Subject: [PATCH] syntax: Better error message for inner attr following doc comment --- src/libsyntax/parse/attr.rs | 70 +++++++++++++++---- .../inner-attr-after-doc-comment.rs | 20 ++++++ src/test/parse-fail/inner-attr.rs | 16 +++++ 3 files changed, 92 insertions(+), 14 deletions(-) create mode 100644 src/test/parse-fail/inner-attr-after-doc-comment.rs create mode 100644 src/test/parse-fail/inner-attr.rs diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs index 15344cef1db..2ae3236cd5a 100644 --- a/src/libsyntax/parse/attr.rs +++ b/src/libsyntax/parse/attr.rs @@ -18,23 +18,43 @@ use parse::token; use parse::parser::{Parser, TokenType}; use ptr::P; +#[derive(PartialEq, Eq, Debug)] +enum InnerAttributeParsePolicy<'a> { + Permitted, + NotPermitted { reason: &'a str }, +} + +const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &'static str = "an inner attribute is not \ + permitted in this context"; + impl<'a> Parser<'a> { /// Parse attributes that appear before an item pub fn parse_outer_attributes(&mut self) -> PResult<'a, Vec> { let mut attrs: Vec = Vec::new(); + let mut just_parsed_doc_comment = false; loop { debug!("parse_outer_attributes: self.token={:?}", self.token); match self.token { token::Pound => { - attrs.push(self.parse_attribute(false)?); + let inner_error_reason = if just_parsed_doc_comment { + "an inner attribute is not permitted following an outer doc comment" + } else if !attrs.is_empty() { + "an inner attribute is not permitted following an outer attribute" + } else { + DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG + }; + let inner_parse_policy = + InnerAttributeParsePolicy::NotPermitted { reason: inner_error_reason }; + attrs.push(self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?); + just_parsed_doc_comment = false; } token::DocComment(s) => { let attr = ::attr::mk_sugared_doc_attr( - attr::mk_attr_id(), - self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), - self.span.lo, - self.span.hi - ); + attr::mk_attr_id(), + self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), + self.span.lo, + self.span.hi + ); if attr.node.style != ast::AttrStyle::Outer { let mut err = self.fatal("expected outer doc comment"); err.note("inner doc comments like this (starting with \ @@ -43,6 +63,7 @@ impl<'a> Parser<'a> { } attrs.push(attr); self.bump(); + just_parsed_doc_comment = true; } _ => break, } @@ -55,26 +76,46 @@ impl<'a> Parser<'a> { /// If permit_inner is true, then a leading `!` indicates an inner /// attribute pub fn parse_attribute(&mut self, permit_inner: bool) -> PResult<'a, ast::Attribute> { - debug!("parse_attributes: permit_inner={:?} self.token={:?}", + debug!("parse_attribute: permit_inner={:?} self.token={:?}", permit_inner, self.token); + let inner_parse_policy = if permit_inner { + InnerAttributeParsePolicy::Permitted + } else { + InnerAttributeParsePolicy::NotPermitted + { reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG } + }; + self.parse_attribute_with_inner_parse_policy(inner_parse_policy) + } + + /// The same as `parse_attribute`, except it takes in an `InnerAttributeParsePolicy` + /// that prescribes how to handle inner attributes. + fn parse_attribute_with_inner_parse_policy(&mut self, + inner_parse_policy: InnerAttributeParsePolicy) + -> PResult<'a, ast::Attribute> { + debug!("parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}", + inner_parse_policy, + self.token); let (span, value, mut style) = match self.token { token::Pound => { let lo = self.span.lo; self.bump(); - if permit_inner { + if inner_parse_policy == InnerAttributeParsePolicy::Permitted { self.expected_tokens.push(TokenType::Token(token::Not)); } let style = if self.token == token::Not { self.bump(); - if !permit_inner { + if let InnerAttributeParsePolicy::NotPermitted { reason } = inner_parse_policy + { let span = self.span; self.diagnostic() - .struct_span_err(span, - "an inner attribute is not permitted in this context") - .help("place inner attribute at the top of the module or \ - block") + .struct_span_err(span, reason) + .note("inner attributes and doc comments, like `#![no_std]` or \ + `//! My crate`, annotate the item enclosing them, and are \ + usually found at the beginning of source files. Outer \ + attributes and doc comments, like `#[test]` and + `/// My function`, annotate the item following them.") .emit() } ast::AttrStyle::Inner @@ -95,7 +136,8 @@ impl<'a> Parser<'a> { } }; - if permit_inner && self.token == token::Semi { + if inner_parse_policy == InnerAttributeParsePolicy::Permitted && + self.token == token::Semi { self.bump(); self.span_warn(span, "this inner attribute syntax is deprecated. The new syntax is \ diff --git a/src/test/parse-fail/inner-attr-after-doc-comment.rs b/src/test/parse-fail/inner-attr-after-doc-comment.rs new file mode 100644 index 00000000000..ed8342d9f5a --- /dev/null +++ b/src/test/parse-fail/inner-attr-after-doc-comment.rs @@ -0,0 +1,20 @@ +// Copyright 2016 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// compile-flags: -Z parse-only + +#![feature(lang_items)] +/** + * My module + */ + +#![recursion_limit="100"] +//~^ ERROR an inner attribute is not permitted following an outer doc comment +fn main() {} diff --git a/src/test/parse-fail/inner-attr.rs b/src/test/parse-fail/inner-attr.rs new file mode 100644 index 00000000000..8cebda66445 --- /dev/null +++ b/src/test/parse-fail/inner-attr.rs @@ -0,0 +1,16 @@ +// Copyright 2016 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// compile-flags: -Z parse-only + +#[feature(lang_items)] + +#![recursion_limit="100"] //~ ERROR an inner attribute is not permitted following an outer attribute +fn main() {}