Rollup merge of #67781 - cjgillot:passes-const, r=oli-obk

Move `is_min_const_fn` query to librustc_mir.

The only two uses of the associated methods are in `librustc_mir` and
`librustdoc`. Please tell me if there is a better choice.

cc #65031

2 files changed, 0 insertions, 158 deletions

diff --git a/src/librustc/ty/constness.rs b/src/librustc/ty/constness.rs
deleted file mode 100644
index cc5131cb217..00000000000
--- a/src/librustc/ty/constness.rs
+++ /dev/null
@@ -1,156 +0,0 @@
-use crate::hir::map::blocks::FnLikeNode;
-use crate::ty::query::Providers;
-use crate::ty::TyCtxt;
-use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
-use rustc_span::symbol::Symbol;
-use rustc_target::spec::abi::Abi;
-use syntax::attr;
-
-impl<'tcx> TyCtxt<'tcx> {
-    /// Whether the `def_id` counts as const fn in your current crate, considering all active
-    /// feature gates
-    pub fn is_const_fn(self, def_id: DefId) -> bool {
-        self.is_const_fn_raw(def_id)
-            && match self.is_unstable_const_fn(def_id) {
-                Some(feature_name) => {
-                    // has a `rustc_const_unstable` attribute, check whether the user enabled the
-                    // corresponding feature gate.
-                    self.features()
-                        .declared_lib_features
-                        .iter()
-                        .any(|&(sym, _)| sym == feature_name)
-                }
-                // functions without const stability are either stable user written
-                // const fn or the user is using feature gates and we thus don't
-                // care what they do
-                None => true,
-            }
-    }
-
-    /// Whether the `def_id` is an unstable const fn and what feature gate is necessary to enable it
-    pub fn is_unstable_const_fn(self, def_id: DefId) -> Option<Symbol> {
-        if self.is_const_fn_raw(def_id) {
-            let const_stab = self.lookup_const_stability(def_id)?;
-            if const_stab.level.is_unstable() { Some(const_stab.feature) } else { None }
-        } else {
-            None
-        }
-    }
-
-    /// Returns `true` if this function must conform to `min_const_fn`
-    pub fn is_min_const_fn(self, def_id: DefId) -> bool {
-        // Bail out if the signature doesn't contain `const`
-        if !self.is_const_fn_raw(def_id) {
-            return false;
-        }
-
-        if self.features().staged_api {
-            // In order for a libstd function to be considered min_const_fn
-            // it needs to be stable and have no `rustc_const_unstable` attribute.
-            match self.lookup_const_stability(def_id) {
-                // `rustc_const_unstable` functions don't need to conform.
-                Some(&attr::ConstStability { ref level, .. }) if level.is_unstable() => false,
-                None => {
-                    if let Some(stab) = self.lookup_stability(def_id) {
-                        if stab.level.is_stable() {
-                            self.sess.span_err(
-                                self.def_span(def_id),
-                                "stable const functions must have either `rustc_const_stable` or \
-                            `rustc_const_unstable` attribute",
-                            );
-                            // While we errored above, because we don't know if we need to conform, we
-                            // err on the "safe" side and require min_const_fn.
-                            true
-                        } else {
-                            // Unstable functions need not conform to min_const_fn.
-                            false
-                        }
-                    } else {
-                        // Internal functions are forced to conform to min_const_fn.
-                        // Annotate the internal function with a const stability attribute if
-                        // you need to use unstable features.
-                        // Note: this is an arbitrary choice that does not affect stability or const
-                        // safety or anything, it just changes whether we need to annotate some
-                        // internal functions with `rustc_const_stable` or with `rustc_const_unstable`
-                        true
-                    }
-                }
-                // Everything else needs to conform, because it would be callable from
-                // other `min_const_fn` functions.
-                _ => true,
-            }
-        } else {
-            // users enabling the `const_fn` feature gate can do what they want
-            !self.features().const_fn
-        }
-    }
-}
-
-pub fn provide(providers: &mut Providers<'_>) {
-    /// Const evaluability whitelist is here to check evaluability at the
-    /// top level beforehand.
-    fn is_const_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> Option<bool> {
-        match tcx.fn_sig(def_id).abi() {
-            Abi::RustIntrinsic | Abi::PlatformIntrinsic => {
-                Some(tcx.lookup_const_stability(def_id).is_some())
-            }
-            _ => None,
-        }
-    }
-
-    /// Checks whether the function has a `const` modifier or, in case it is an intrinsic, whether
-    /// said intrinsic is on the whitelist for being const callable.
-    fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-        let hir_id = tcx
-            .hir()
-            .as_local_hir_id(def_id)
-            .expect("Non-local call to local provider is_const_fn");
-
-        let node = tcx.hir().get(hir_id);
-
-        if let Some(whitelisted) = is_const_intrinsic(tcx, def_id) {
-            whitelisted
-        } else if let Some(fn_like) = FnLikeNode::from_node(node) {
-            fn_like.constness() == hir::Constness::Const
-        } else if let hir::Node::Ctor(_) = node {
-            true
-        } else {
-            false
-        }
-    }
-
-    fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-        tcx.is_const_fn(def_id)
-            && match tcx.lookup_const_stability(def_id) {
-                Some(stab) => {
-                    if cfg!(debug_assertions) && stab.promotable {
-                        let sig = tcx.fn_sig(def_id);
-                        assert_eq!(
-                            sig.unsafety(),
-                            hir::Unsafety::Normal,
-                            "don't mark const unsafe fns as promotable",
-                            // https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
-                        );
-                    }
-                    stab.promotable
-                }
-                None => false,
-            }
-    }
-
-    fn const_fn_is_allowed_fn_ptr(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-        tcx.is_const_fn(def_id)
-            && tcx
-                .lookup_const_stability(def_id)
-                .map(|stab| stab.allow_const_fn_ptr)
-                .unwrap_or(false)
-    }
-
-    *providers = Providers {
-        is_const_fn_raw,
-        is_promotable_const_fn,
-        const_fn_is_allowed_fn_ptr,
-        ..*providers
-    };
-}
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 7cca12308e6..747e6e8da99 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -97,7 +97,6 @@ pub mod cast;
 #[macro_use]
 pub mod codec;
 pub mod _match;
-mod constness;
 mod erase_regions;
 pub mod error;
 pub mod fast_reject;
@@ -3318,7 +3317,6 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
     context::provide(providers);
     erase_regions::provide(providers);
     layout::provide(providers);
-    constness::provide(providers);
     *providers = ty::query::Providers {
         asyncness,
         associated_item,