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Rollup merge of rust-lang#54683 - zackmdavis:critique_of_pure_lints, …
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…r=petrochenkov

lint reasons (RFC 2883, part 1)

This implements the `reason =` functionality described in [the RFC](https://github.com/rust-lang/rfcs/blob/master/text/2383-lint-reasons.md) under a `lint_reasons` feature gate.

![lint_reasons_pt_1](https://user-images.githubusercontent.com/1076988/46252097-eed51000-c418-11e8-8212-939d3f02f95d.png)
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Mark-Simulacrum authored Oct 27, 2018
2 parents cae6efc + f66ea66 commit 80c1f0b
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Showing 12 changed files with 304 additions and 20 deletions.
99 changes: 82 additions & 17 deletions src/librustc/lint/levels.rs
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ use rustc_data_structures::stable_hasher::{HashStable, ToStableHashKey,
use session::Session;
use syntax::ast;
use syntax::attr;
use syntax::feature_gate;
use syntax::source_map::MultiSpan;
use syntax::symbol::Symbol;
use util::nodemap::FxHashMap;
Expand Down Expand Up @@ -199,8 +200,7 @@ impl<'a> LintLevelsBuilder<'a> {
let store = self.sess.lint_store.borrow();
let sess = self.sess;
let bad_attr = |span| {
span_err!(sess, span, E0452,
"malformed lint attribute");
struct_span_err!(sess, span, E0452, "malformed lint attribute")
};
for attr in attrs {
let level = match Level::from_str(&attr.name().as_str()) {
Expand All @@ -211,19 +211,76 @@ impl<'a> LintLevelsBuilder<'a> {
let meta = unwrap_or!(attr.meta(), continue);
attr::mark_used(attr);

let metas = if let Some(metas) = meta.meta_item_list() {
let mut metas = if let Some(metas) = meta.meta_item_list() {
metas
} else {
bad_attr(meta.span);
continue
let mut err = bad_attr(meta.span);
err.emit();
continue;
};

if metas.is_empty() {
// FIXME (#55112): issue unused-attributes lint for `#[level()]`
continue;
}

// Before processing the lint names, look for a reason (RFC 2383)
// at the end.
let mut reason = None;
let tail_li = &metas[metas.len()-1];
if let Some(item) = tail_li.meta_item() {
match item.node {
ast::MetaItemKind::Word => {} // actual lint names handled later
ast::MetaItemKind::NameValue(ref name_value) => {
let gate_reasons = !self.sess.features_untracked().lint_reasons;
if item.ident == "reason" {
// found reason, reslice meta list to exclude it
metas = &metas[0..metas.len()-1];
// FIXME (#55112): issue unused-attributes lint if we thereby
// don't have any lint names (`#[level(reason = "foo")]`)
if let ast::LitKind::Str(rationale, _) = name_value.node {
if gate_reasons {
feature_gate::emit_feature_err(
&self.sess.parse_sess,
"lint_reasons",
item.span,
feature_gate::GateIssue::Language,
"lint reasons are experimental"
);
} else {
reason = Some(rationale);
}
} else {
let mut err = bad_attr(name_value.span);
err.help("reason must be a string literal");
err.emit();
}
} else {
let mut err = bad_attr(item.span);
err.emit();
}
},
ast::MetaItemKind::List(_) => {
let mut err = bad_attr(item.span);
err.emit();
}
}
}

for li in metas {
let word = match li.word() {
Some(word) => word,
None => {
bad_attr(li.span);
continue
let mut err = bad_attr(li.span);
if let Some(item) = li.meta_item() {
if let ast::MetaItemKind::NameValue(_) = item.node {
if item.ident == "reason" {
err.help("reason in lint attribute must come last");
}
}
}
err.emit();
continue;
}
};
let tool_name = if let Some(lint_tool) = word.is_scoped() {
Expand All @@ -245,7 +302,7 @@ impl<'a> LintLevelsBuilder<'a> {
let name = word.name();
match store.check_lint_name(&name.as_str(), tool_name) {
CheckLintNameResult::Ok(ids) => {
let src = LintSource::Node(name, li.span);
let src = LintSource::Node(name, li.span, reason);
for id in ids {
specs.insert(*id, (level, src));
}
Expand All @@ -255,7 +312,9 @@ impl<'a> LintLevelsBuilder<'a> {
match result {
Ok(ids) => {
let complete_name = &format!("{}::{}", tool_name.unwrap(), name);
let src = LintSource::Node(Symbol::intern(complete_name), li.span);
let src = LintSource::Node(
Symbol::intern(complete_name), li.span, reason
);
for id in ids {
specs.insert(*id, (level, src));
}
Expand Down Expand Up @@ -286,7 +345,9 @@ impl<'a> LintLevelsBuilder<'a> {
Applicability::MachineApplicable,
).emit();

let src = LintSource::Node(Symbol::intern(&new_lint_name), li.span);
let src = LintSource::Node(
Symbol::intern(&new_lint_name), li.span, reason
);
for id in ids {
specs.insert(*id, (level, src));
}
Expand Down Expand Up @@ -368,11 +429,11 @@ impl<'a> LintLevelsBuilder<'a> {
};
let forbidden_lint_name = match forbid_src {
LintSource::Default => id.to_string(),
LintSource::Node(name, _) => name.to_string(),
LintSource::Node(name, _, _) => name.to_string(),
LintSource::CommandLine(name) => name.to_string(),
};
let (lint_attr_name, lint_attr_span) = match *src {
LintSource::Node(name, span) => (name, span),
LintSource::Node(name, span, _) => (name, span),
_ => continue,
};
let mut diag_builder = struct_span_err!(self.sess,
Expand All @@ -384,15 +445,19 @@ impl<'a> LintLevelsBuilder<'a> {
forbidden_lint_name);
diag_builder.span_label(lint_attr_span, "overruled by previous forbid");
match forbid_src {
LintSource::Default => &mut diag_builder,
LintSource::Node(_, forbid_source_span) => {
LintSource::Default => {},
LintSource::Node(_, forbid_source_span, reason) => {
diag_builder.span_label(forbid_source_span,
"`forbid` level set here")
"`forbid` level set here");
if let Some(rationale) = reason {
diag_builder.note(&rationale.as_str());
}
},
LintSource::CommandLine(_) => {
diag_builder.note("`forbid` lint level was set on command line")
diag_builder.note("`forbid` lint level was set on command line");
}
}.emit();
}
diag_builder.emit();
// don't set a separate error for every lint in the group
break
}
Expand Down
9 changes: 6 additions & 3 deletions src/librustc/lint/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -470,15 +470,15 @@ pub enum LintSource {
Default,

/// Lint level was set by an attribute.
Node(ast::Name, Span),
Node(ast::Name, Span, Option<Symbol> /* RFC 2383 reason */),

/// Lint level was set by a command-line flag.
CommandLine(Symbol),
}

impl_stable_hash_for!(enum self::LintSource {
Default,
Node(name, span),
Node(name, span, reason),
CommandLine(text)
});

Expand Down Expand Up @@ -578,7 +578,10 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
hyphen_case_flag_val));
}
}
LintSource::Node(lint_attr_name, src) => {
LintSource::Node(lint_attr_name, src, reason) => {
if let Some(rationale) = reason {
err.note(&rationale.as_str());
}
sess.diag_span_note_once(&mut err, DiagnosticMessageId::from(lint),
src, "lint level defined here");
if lint_attr_name.as_str() != name {
Expand Down
3 changes: 3 additions & 0 deletions src/libsyntax/feature_gate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -504,6 +504,9 @@ declare_features! (

// `extern crate foo as bar;` puts `bar` into extern prelude.
(active, extern_crate_item_prelude, "1.31.0", Some(54658), None),

// `reason = ` in lint attributes and `expect` lint attribute
(active, lint_reasons, "1.31.0", Some(54503), None),
);

declare_features! (
Expand Down
4 changes: 4 additions & 0 deletions src/test/ui/feature-gates/feature-gate-lint-reasons.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
#![warn(nonstandard_style, reason = "the standard should be respected")]
//~^ ERROR lint reasons are experimental

fn main() {}
11 changes: 11 additions & 0 deletions src/test/ui/feature-gates/feature-gate-lint-reasons.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
error[E0658]: lint reasons are experimental (see issue #54503)
--> $DIR/feature-gate-lint-reasons.rs:1:28
|
LL | #![warn(nonstandard_style, reason = "the standard should be respected")]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(lint_reasons)] to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.
17 changes: 17 additions & 0 deletions src/test/ui/lint/empty-lint-attributes.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
#![feature(lint_reasons)]

// run-pass

// Empty (and reason-only) lint attributes are legal—although we may want to
// lint them in the future (Issue #55112).

#![allow()]
#![warn(reason = "observationalism")]

#[forbid()]
fn devoir() {}

#[deny(reason = "ultion")]
fn waldgrave() {}

fn main() {}
24 changes: 24 additions & 0 deletions src/test/ui/lint/reasons-erroneous.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
#![feature(lint_reasons)]

#![warn(absolute_paths_not_starting_with_crate, reason = 0)]
//~^ ERROR malformed lint attribute
//~| HELP reason must be a string literal
#![warn(anonymous_parameters, reason = b"consider these, for we have condemned them")]
//~^ ERROR malformed lint attribute
//~| HELP reason must be a string literal
#![warn(bare_trait_objects, reasons = "leaders to no sure land, guides their bearings lost")]
//~^ ERROR malformed lint attribute
#![warn(box_pointers, blerp = "or in league with robbers have reversed the signposts")]
//~^ ERROR malformed lint attribute
#![warn(elided_lifetimes_in_paths, reason("disrespectful to ancestors", "irresponsible to heirs"))]
//~^ ERROR malformed lint attribute
#![warn(ellipsis_inclusive_range_patterns, reason = "born barren", reason = "a freak growth")]
//~^ ERROR malformed lint attribute
//~| HELP reason in lint attribute must come last
#![warn(keyword_idents, reason = "root in rubble", macro_use_extern_crate)]
//~^ ERROR malformed lint attribute
//~| HELP reason in lint attribute must come last
#![warn(missing_copy_implementations, reason)]
//~^ WARN unknown lint

fn main() {}
61 changes: 61 additions & 0 deletions src/test/ui/lint/reasons-erroneous.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:3:58
|
LL | #![warn(absolute_paths_not_starting_with_crate, reason = 0)]
| ^
|
= help: reason must be a string literal

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:6:40
|
LL | #![warn(anonymous_parameters, reason = b"consider these, for we have condemned them")]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: reason must be a string literal

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:9:29
|
LL | #![warn(bare_trait_objects, reasons = "leaders to no sure land, guides their bearings lost")]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:11:23
|
LL | #![warn(box_pointers, blerp = "or in league with robbers have reversed the signposts")]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:13:36
|
LL | #![warn(elided_lifetimes_in_paths, reason("disrespectful to ancestors", "irresponsible to heirs"))]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:15:44
|
LL | #![warn(ellipsis_inclusive_range_patterns, reason = "born barren", reason = "a freak growth")]
| ^^^^^^^^^^^^^^^^^^^^^^
|
= help: reason in lint attribute must come last

error[E0452]: malformed lint attribute
--> $DIR/reasons-erroneous.rs:18:25
|
LL | #![warn(keyword_idents, reason = "root in rubble", macro_use_extern_crate)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: reason in lint attribute must come last

warning: unknown lint: `reason`
--> $DIR/reasons-erroneous.rs:21:39
|
LL | #![warn(missing_copy_implementations, reason)]
| ^^^^^^
|
= note: #[warn(unknown_lints)] on by default

error: aborting due to 7 previous errors

For more information about this error, try `rustc --explain E0452`.
21 changes: 21 additions & 0 deletions src/test/ui/lint/reasons-forbidden.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
#![feature(lint_reasons)]

#![forbid(
unsafe_code,
//~^ NOTE `forbid` level set here
reason = "our errors & omissions insurance policy doesn't cover unsafe Rust"
)]

use std::ptr;

fn main() {
let a_billion_dollar_mistake = ptr::null();

#[allow(unsafe_code)]
//~^ ERROR allow(unsafe_code) overruled by outer forbid(unsafe_code)
//~| NOTE overruled by previous forbid
//~| NOTE our errors & omissions insurance policy doesn't cover unsafe Rust
unsafe {
*a_billion_dollar_mistake
}
}
14 changes: 14 additions & 0 deletions src/test/ui/lint/reasons-forbidden.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0453]: allow(unsafe_code) overruled by outer forbid(unsafe_code)
--> $DIR/reasons-forbidden.rs:14:13
|
LL | unsafe_code,
| ----------- `forbid` level set here
...
LL | #[allow(unsafe_code)]
| ^^^^^^^^^^^ overruled by previous forbid
|
= note: our errors & omissions insurance policy doesn't cover unsafe Rust

error: aborting due to previous error

For more information about this error, try `rustc --explain E0453`.
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