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--print option to list available feature gates
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The option is only made available on nightly builds, for the obvious
reason. While we're here, also prevent the unstable `target-spec-json`
(tracking issue rust-lang#38338) from showing up in the --help on stable builds
(although the way in which we accomplish this is slightly clumsy for
lifetime reasons, as noted in the FIXME).

We make REMOVED_FEATURES, ACCEPTED_FEATURES, &c. public for consistency,
even though the functionality at issue only needs ACTIVE_FEATURES.

The UI test will add a little bit of friction for future feature
developers, but it's better than under-testing.

Resolves rust-lang#38768.
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@zackmdavis
zackmdavis committed Oct 12, 2017
1 parent cbf5d39 commit cfe0033
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Showing 5 changed files with 185 additions and 9 deletions.
31 changes: 27 additions & 4 deletions src/librustc/session/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -369,6 +369,7 @@ pub enum PrintRequest {
CodeModels,
TargetSpec,
NativeStaticLibs,
UnstableFeatures,
}

pub enum Input {
Expand Down Expand Up @@ -1306,6 +1307,17 @@ mod opt {
/// including metadata for each option, such as whether the option is
/// part of the stable long-term interface for rustc.
pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
// FIXME: unfortunately, we need to hardcode these nightly vs. stable
// option value listings separately (rather than, say, plumbing in the
// extra nightly values with `format!`) because the `opt` interface
// requires a static lifetime
let stable_print_options = "[crate-name|file-names|sysroot|cfg|target-list|\
target-cpus|target-features|relocation-models|\
code-models|native-static-libs]";
let nightly_print_options = "[crate-name|file-names|sysroot|cfg|target-list|\
target-cpus|target-features|relocation-models|\
code-models|native-static-libs|target-spec-json|\
unstable-features]";
vec![
opt::flag_s("h", "help", "Display this message"),
opt::multi_s("", "cfg", "Configure the compilation environment", "SPEC"),
Expand All @@ -1325,10 +1337,12 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
the compiler to emit",
"[asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]"),
opt::multi_s("", "print", "Comma separated list of compiler information to \
print on stdout",
"[crate-name|file-names|sysroot|cfg|target-list|\
target-cpus|target-features|relocation-models|\
code-models|target-spec-json|native-static-libs]"),
print on stdout",
if nightly_options::is_nightly_build() {
nightly_print_options
} else {
stable_print_options
}),
opt::flagmulti_s("g", "", "Equivalent to -C debuginfo=2"),
opt::flagmulti_s("O", "", "Equivalent to -C opt-level=2"),
opt::opt_s("o", "", "Write output to <filename>", "FILENAME"),
Expand Down Expand Up @@ -1679,6 +1693,15 @@ pub fn build_session_options_and_crate_config(matches: &getopts::Matches)
enable the target-spec-json print option"));
}
},
"unstable-features" => {
if nightly_options::is_nightly_build() {
PrintRequest::UnstableFeatures
} else {
early_error(error_format,
&format!("unstable features require a nightly \
build of the compiler"));
}
},
req => {
early_error(error_format, &format!("unknown print request `{}`", req))
}
Expand Down
34 changes: 33 additions & 1 deletion src/librustc_driver/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,7 @@ use std::thread;

use syntax::ast;
use syntax::codemap::{CodeMap, FileLoader, RealFileLoader};
use syntax::feature_gate::{GatedCfg, UnstableFeatures};
use syntax::feature_gate::{ACTIVE_FEATURES, GatedCfg, UnstableFeatures};
use syntax::parse::{self, PResult};
use syntax_pos::{DUMMY_SP, MultiSpan};

Expand Down Expand Up @@ -801,6 +801,38 @@ impl RustcDefaultCalls {
PrintRequest::NativeStaticLibs => {
println!("Native static libs can be printed only during linking");
}
PrintRequest::UnstableFeatures => {
let (feat_width, ver_width, iss_width) = ACTIVE_FEATURES.iter()
.map(|&(feat, ver, iss_maybe, _)| {
(feat.len(),
ver.len(),
iss_maybe.map(|no| no.to_string().len()).unwrap_or(1))
})
.fold((7, 7, 5), // lengths of col. headings: "feature", "version", "issue"
|max_widths, feat_widths| {
(max(max_widths.0, feat_widths.0),
max(max_widths.1, feat_widths.1),
max(max_widths.2, feat_widths.2))
});
println!("| {0:feat_width$} | {1:ver_width$} | {2:iss_width$} |",
"feature", "version", "issue",
feat_width = feat_width,
ver_width = ver_width,
iss_width = iss_width);
println!("{:->total_width$}", "",
// `+ 10` is for ` | ` column borders: 2 + 3 + 3 + 2
total_width = feat_width + ver_width + iss_width + 10);
let mut features = ACTIVE_FEATURES.to_vec();
features.sort_by_key(|&f| f.0);
for &(feature, version, issue_maybe, _) in &features {
println!("| {0:feat_width$} | {1:>ver_width$} | {2:>iss_width$} |",
feature, version,
issue_maybe.map(|no| no.to_string()).unwrap_or("—".to_owned()),
feat_width = feat_width,
ver_width = ver_width,
iss_width = iss_width);
}
}
}
}
return Compilation::Stop;
Expand Down
8 changes: 4 additions & 4 deletions src/libsyntax/feature_gate.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ macro_rules! declare_features {
($((active, $feature: ident, $ver: expr, $issue: expr),)+) => {
/// Represents active features that are currently being implemented or
/// currently being considered for addition/removal.
const ACTIVE_FEATURES:
pub const ACTIVE_FEATURES:
&'static [(&'static str, &'static str, Option<u32>, fn(&mut Features, Span))] =
&[$((stringify!($feature), $ver, $issue, set!($feature))),+];

Expand All @@ -84,21 +84,21 @@ macro_rules! declare_features {

($((removed, $feature: ident, $ver: expr, $issue: expr),)+) => {
/// Represents unstable features which have since been removed (it was once Active)
const REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
pub const REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
$((stringify!($feature), $ver, $issue)),+
];
};

($((stable_removed, $feature: ident, $ver: expr, $issue: expr),)+) => {
/// Represents stable features which have since been removed (it was once Accepted)
const STABLE_REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
pub const STABLE_REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
$((stringify!($feature), $ver, $issue)),+
];
};

($((accepted, $feature: ident, $ver: expr, $issue: expr),)+) => {
/// Those language feature has since been Accepted (it was once Active)
const ACCEPTED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
pub const ACCEPTED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
$((stringify!($feature), $ver, $issue)),+
];
}
Expand Down
13 changes: 13 additions & 0 deletions src/test/ui/print/unstable-features.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// compile-flags: --print unstable-features

fn main() {}
108 changes: 108 additions & 0 deletions src/test/ui/print/unstable-features.stdout
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@@ -0,0 +1,108 @@
| feature | version | issue |
-----------------------------------------------------
| abi_msp430_interrupt | 1.16.0 | 38487 |
| abi_ptx | 1.15.0 | — |
| abi_sysv64 | 1.13.0 | 36167 |
| abi_thiscall | 1.19.0 | — |
| abi_unadjusted | 1.16.0 | — |
| abi_vectorcall | 1.7.0 | — |
| abi_x86_interrupt | 1.17.0 | 40180 |
| advanced_slice_patterns | 1.0.0 | 23121 |
| allocator_internals | 1.20.0 | — |
| allow_fail | 1.19.0 | 42219 |
| allow_internal_unsafe | 1.0.0 | — |
| allow_internal_unstable | 1.0.0 | — |
| asm | 1.0.0 | 29722 |
| associated_type_defaults | 1.2.0 | 29661 |
| attr_literals | 1.13.0 | 34981 |
| box_patterns | 1.0.0 | 29641 |
| box_syntax | 1.0.0 | 27779 |
| catch_expr | 1.17.0 | 31436 |
| cfg_target_feature | 1.4.0 | 29717 |
| cfg_target_has_atomic | 1.9.0 | 32976 |
| cfg_target_thread_local | 1.7.0 | 29594 |
| cfg_target_vendor | 1.5.0 | 29718 |
| clone_closures | 1.22.0 | 44490 |
| compiler_builtins | 1.13.0 | — |
| concat_idents | 1.0.0 | 29599 |
| conservative_impl_trait | 1.12.0 | 34511 |
| const_fn | 1.2.0 | 24111 |
| const_indexing | 1.4.0 | 29947 |
| copy_closures | 1.22.0 | 44490 |
| custom_attribute | 1.0.0 | 29642 |
| custom_derive | 1.0.0 | 29644 |
| decl_macro | 1.17.0 | 39412 |
| default_type_parameter_fallback | 1.3.0 | 27336 |
| doc_cfg | 1.21.0 | 43781 |
| doc_masked | 1.21.0 | 44027 |
| dotdoteq_in_patterns | 1.22.0 | 28237 |
| dropck_eyepatch | 1.10.0 | 34761 |
| dropck_parametricity | 1.3.0 | 28498 |
| exclusive_range_pattern | 1.11.0 | 37854 |
| fn_must_use | 1.21.0 | 43302 |
| fundamental | 1.0.0 | 29635 |
| generators | 1.21.0 | — |
| generic_param_attrs | 1.11.0 | 34761 |
| global_allocator | 1.20.0 | — |
| global_asm | 1.18.0 | 35119 |
| i128_type | 1.16.0 | 35118 |
| inclusive_range_syntax | 1.7.0 | 28237 |
| intrinsics | 1.0.0 | — |
| lang_items | 1.0.0 | — |
| link_args | 1.0.0 | 29596 |
| link_cfg | 1.14.0 | 37406 |
| link_llvm_intrinsics | 1.0.0 | 29602 |
| linkage | 1.0.0 | 29603 |
| log_syntax | 1.0.0 | 29598 |
| macro_reexport | 1.0.0 | 29638 |
| macro_vis_matcher | 1.18.0 | 41022 |
| main | 1.0.0 | 29634 |
| match_beginning_vert | 1.21.0 | 44101 |
| match_default_bindings | 1.22.0 | 42640 |
| naked_functions | 1.9.0 | 32408 |
| needs_allocator | 1.4.0 | 27389 |
| needs_panic_runtime | 1.10.0 | 32837 |
| never_type | 1.13.0 | 35121 |
| no_core | 1.3.0 | 29639 |
| no_debug | 1.5.0 | 29721 |
| non_ascii_idents | 1.0.0 | 28979 |
| omit_gdb_pretty_printer_section | 1.5.0 | — |
| on_unimplemented | 1.0.0 | 29628 |
| optin_builtin_traits | 1.0.0 | 13231 |
| overlapping_marker_traits | 1.18.0 | 29864 |
| panic_runtime | 1.10.0 | 32837 |
| placement_in_syntax | 1.0.0 | 27779 |
| platform_intrinsics | 1.4.0 | 27731 |
| plugin | 1.0.0 | 29597 |
| plugin_registrar | 1.0.0 | 29597 |
| prelude_import | 1.2.0 | — |
| proc_macro | 1.16.0 | 38356 |
| profiler_runtime | 1.18.0 | — |
| quote | 1.0.0 | 29601 |
| repr128 | 1.16.0 | 35118 |
| repr_align | 1.17.0 | 33626 |
| repr_simd | 1.4.0 | 27731 |
| rustc_attrs | 1.0.0 | 29642 |
| rustc_const_unstable | 1.0.0 | — |
| rustc_diagnostic_macros | 1.0.0 | — |
| sanitizer_runtime | 1.17.0 | — |
| simd | 1.0.0 | 27731 |
| simd_ffi | 1.0.0 | 27731 |
| slice_patterns | 1.0.0 | 23121 |
| specialization | 1.7.0 | 31844 |
| staged_api | 1.0.0 | — |
| start | 1.0.0 | 29633 |
| static_nobundle | 1.16.0 | 37403 |
| stmt_expr_attributes | 1.6.0 | 15701 |
| structural_match | 1.8.0 | 31434 |
| target_feature | 1.15.0 | — |
| thread_local | 1.0.0 | 29594 |
| trace_macros | 1.0.0 | 29598 |
| type_ascription | 1.6.0 | 23416 |
| unboxed_closures | 1.0.0 | 29625 |
| underscore_lifetimes | 1.22.0 | 44524 |
| unsized_tuple_coercion | 1.20.0 | 42877 |
| untagged_unions | 1.13.0 | 32836 |
| unwind_attributes | 1.4.0 | — |
| use_extern_macros | 1.15.0 | 35896 |
| used | 1.18.0 | 40289 |

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