From 7435547b253932408193c2e80616a7eddd4ee872 Mon Sep 17 00:00:00 2001 From: David Tolnay Date: Tue, 21 Apr 2020 12:28:11 -0700 Subject: [PATCH 1/2] proc_macro::is_available() --- src/libproc_macro/bridge/client.rs | 7 +++++++ src/libproc_macro/lib.rs | 18 ++++++++++++++++++ .../ui/proc-macro/auxiliary/is-available.rs | 14 ++++++++++++++ src/test/ui/proc-macro/is-available.rs | 17 +++++++++++++++++ 4 files changed, 56 insertions(+) create mode 100644 src/test/ui/proc-macro/auxiliary/is-available.rs create mode 100644 src/test/ui/proc-macro/is-available.rs diff --git a/src/libproc_macro/bridge/client.rs b/src/libproc_macro/bridge/client.rs index 088db92253acf..d2222d12623f9 100644 --- a/src/libproc_macro/bridge/client.rs +++ b/src/libproc_macro/bridge/client.rs @@ -290,6 +290,13 @@ impl BridgeState<'_> { } impl Bridge<'_> { + pub(crate) fn is_available() -> bool { + BridgeState::with(|state| match state { + BridgeState::Connected(_) | BridgeState::InUse => true, + BridgeState::NotConnected => false, + }) + } + fn enter(self, f: impl FnOnce() -> R) -> R { // Hide the default panic output within `proc_macro` expansions. // NB. the server can't do this because it may use a different libstd. diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs index a975ce93bb1a3..fa8087efcea07 100644 --- a/src/libproc_macro/lib.rs +++ b/src/libproc_macro/lib.rs @@ -45,6 +45,24 @@ use std::path::PathBuf; use std::str::FromStr; use std::{error, fmt, iter, mem}; +/// Determines whether proc_macro has been made accessible to the currently +/// running program. +/// +/// The proc_macro crate is only intended for use inside the implementation of +/// procedural macros. All the functions in this crate panic if invoked from +/// outside of a procedural macro, such as from a build script or unit test or +/// ordinary Rust binary. +/// +/// With consideration for Rust libraries that are designed to support both +/// macro and non-macro use cases, `proc_macro::is_available()` provides a +/// non-panicking way to detect whether the infrastructure required to use the +/// API of proc_macro is presently available. Returns true if invoked from +/// inside of a procedural macro, false if invoked from any other binary. +#[unstable(feature = "proc_macro_is_available", issue = "none")] // FIXME +pub fn is_available() -> bool { + bridge::Bridge::is_available() +} + /// The main type provided by this crate, representing an abstract stream of /// tokens, or, more specifically, a sequence of token trees. /// The type provide interfaces for iterating over those token trees and, conversely, diff --git a/src/test/ui/proc-macro/auxiliary/is-available.rs b/src/test/ui/proc-macro/auxiliary/is-available.rs new file mode 100644 index 0000000000000..0caf186db1d5f --- /dev/null +++ b/src/test/ui/proc-macro/auxiliary/is-available.rs @@ -0,0 +1,14 @@ +// force-host +// no-prefer-dynamic + +#![crate_type = "proc-macro"] +#![feature(proc_macro_is_available)] + +extern crate proc_macro; + +use proc_macro::{Literal, TokenStream, TokenTree}; + +#[proc_macro] +pub fn from_inside_proc_macro(_input: TokenStream) -> TokenStream { + proc_macro::is_available().to_string().parse().unwrap() +} diff --git a/src/test/ui/proc-macro/is-available.rs b/src/test/ui/proc-macro/is-available.rs new file mode 100644 index 0000000000000..943d9fe797a6e --- /dev/null +++ b/src/test/ui/proc-macro/is-available.rs @@ -0,0 +1,17 @@ +// run-pass + +#![feature(proc_macro_hygiene, proc_macro_is_available)] + +extern crate proc_macro; + +// aux-build:is-available.rs +extern crate is_available; + +fn main() { + let a = proc_macro::is_available(); + let b = is_available::from_inside_proc_macro!(); + let c = proc_macro::is_available(); + assert!(!a); + assert!(b); + assert!(!c); +} From 3bd742ff4e61f6752d76a75f53c140170a117554 Mon Sep 17 00:00:00 2001 From: David Tolnay Date: Wed, 22 Apr 2020 11:07:07 -0700 Subject: [PATCH 2/2] Add tracking issue for proc_macro_is_available --- src/libproc_macro/lib.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs index fa8087efcea07..3cbe852de7b5a 100644 --- a/src/libproc_macro/lib.rs +++ b/src/libproc_macro/lib.rs @@ -58,7 +58,7 @@ use std::{error, fmt, iter, mem}; /// non-panicking way to detect whether the infrastructure required to use the /// API of proc_macro is presently available. Returns true if invoked from /// inside of a procedural macro, false if invoked from any other binary. -#[unstable(feature = "proc_macro_is_available", issue = "none")] // FIXME +#[unstable(feature = "proc_macro_is_available", issue = "71436")] pub fn is_available() -> bool { bridge::Bridge::is_available() }