rustc_middle/ty/context/
tls.rs

1use std::{mem, ptr};
2
3use rustc_data_structures::sync;
4
5use super::{GlobalCtxt, TyCtxt};
6use crate::dep_graph::TaskDepsRef;
7use crate::query::plumbing::QueryJobId;
8
9/// This is the implicit state of rustc. It contains the current
10/// `TyCtxt` and query. It is updated when creating a local interner or
11/// executing a new query. Whenever there's a `TyCtxt` value available
12/// you should also have access to an `ImplicitCtxt` through the functions
13/// in this module.
14#[derive(Clone)]
15pub struct ImplicitCtxt<'a, 'tcx> {
16    /// The current `TyCtxt`.
17    pub tcx: TyCtxt<'tcx>,
18
19    /// The current query job, if any. This is updated by `JobOwner::start` in
20    /// `ty::query::plumbing` when executing a query.
21    pub query: Option<QueryJobId>,
22
23    /// Used to prevent queries from calling too deeply.
24    pub query_depth: usize,
25
26    /// The current dep graph task. This is used to add dependencies to queries
27    /// when executing them.
28    pub task_deps: TaskDepsRef<'a>,
29}
30
31impl<'a, 'tcx> ImplicitCtxt<'a, 'tcx> {
32    pub fn new(gcx: &'tcx GlobalCtxt<'tcx>) -> Self {
33        let tcx = TyCtxt { gcx };
34        ImplicitCtxt { tcx, query: None, query_depth: 0, task_deps: TaskDepsRef::Ignore }
35    }
36}
37
38// Import the thread-local variable from Rayon, which is preserved for Rayon jobs.
39use rayon_core::tlv::TLV;
40
41#[inline]
42fn erase(context: &ImplicitCtxt<'_, '_>) -> *const () {
43    context as *const _ as *const ()
44}
45
46#[inline]
47unsafe fn downcast<'a, 'tcx>(context: *const ()) -> &'a ImplicitCtxt<'a, 'tcx> {
48    unsafe { &*(context as *const ImplicitCtxt<'a, 'tcx>) }
49}
50
51/// Sets `context` as the new current `ImplicitCtxt` for the duration of the function `f`.
52#[inline]
53pub fn enter_context<'a, 'tcx, F, R>(context: &ImplicitCtxt<'a, 'tcx>, f: F) -> R
54where
55    F: FnOnce() -> R,
56{
57    TLV.with(|tlv| {
58        let old = tlv.replace(erase(context));
59        let _reset = rustc_data_structures::defer(move || tlv.set(old));
60        f()
61    })
62}
63
64/// Allows access to the current `ImplicitCtxt` in a closure if one is available.
65#[inline]
66#[track_caller]
67pub fn with_context_opt<F, R>(f: F) -> R
68where
69    F: for<'a, 'tcx> FnOnce(Option<&ImplicitCtxt<'a, 'tcx>>) -> R,
70{
71    let context = TLV.get();
72    if context.is_null() {
73        f(None)
74    } else {
75        // We could get an `ImplicitCtxt` pointer from another thread.
76        // Ensure that `ImplicitCtxt` is `DynSync`.
77        sync::assert_dyn_sync::<ImplicitCtxt<'_, '_>>();
78
79        unsafe { f(Some(downcast(context))) }
80    }
81}
82
83/// Allows access to the current `ImplicitCtxt`.
84/// Panics if there is no `ImplicitCtxt` available.
85#[inline]
86pub fn with_context<F, R>(f: F) -> R
87where
88    F: for<'a, 'tcx> FnOnce(&ImplicitCtxt<'a, 'tcx>) -> R,
89{
90    with_context_opt(|opt_context| f(opt_context.expect("no ImplicitCtxt stored in tls")))
91}
92
93/// Allows access to the current `ImplicitCtxt` whose tcx field is the same as the tcx argument
94/// passed in. This means the closure is given an `ImplicitCtxt` with the same `'tcx` lifetime
95/// as the `TyCtxt` passed in.
96/// This will panic if you pass it a `TyCtxt` which is different from the current
97/// `ImplicitCtxt`'s `tcx` field.
98#[inline]
99pub fn with_related_context<'tcx, F, R>(tcx: TyCtxt<'tcx>, f: F) -> R
100where
101    F: FnOnce(&ImplicitCtxt<'_, 'tcx>) -> R,
102{
103    with_context(|context| {
104        // The two gcx have different invariant lifetimes, so we need to erase them for the comparison.
105        assert!(ptr::eq(
106            context.tcx.gcx as *const _ as *const (),
107            tcx.gcx as *const _ as *const ()
108        ));
109
110        let context: &ImplicitCtxt<'_, '_> = unsafe { mem::transmute(context) };
111
112        f(context)
113    })
114}
115
116/// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
117/// Panics if there is no `ImplicitCtxt` available.
118#[inline]
119pub fn with<F, R>(f: F) -> R
120where
121    F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> R,
122{
123    with_context(|context| f(context.tcx))
124}
125
126/// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
127/// The closure is passed None if there is no `ImplicitCtxt` available.
128#[inline]
129#[track_caller]
130pub fn with_opt<F, R>(f: F) -> R
131where
132    F: for<'tcx> FnOnce(Option<TyCtxt<'tcx>>) -> R,
133{
134    with_context_opt(
135        #[track_caller]
136        |opt_context| f(opt_context.map(|context| context.tcx)),
137    )
138}
rustc_middle/ty/context/tls.rs

rustc_middle/ty/context/
tls.rs
