Auto merge of #68115 - Centril:rollup-e2fszdv, r=Centril

Rollup of 8 pull requests

Successful merges:

 - #67666 (make use of pointer::is_null)
 - #67806 (Extract `rustc_ast_passes`, move gating, & refactor linting)
 - #68043 (Add some missing timers)
 - #68074 (Add `llvm-skip-rebuild` flag to `x.py`)
 - #68079 (Clarify suggestion for E0013)
 - #68084 (Do not ICE on unicode next point)
 - #68102 (Inline some conversion methods around OsStr)
 - #68106 (Fix issue with using `self` module via indirection)

Failed merges:

r? @ghost

5 files changed, 1 insertions, 1071 deletions

diff --git a/src/libsyntax/attr/builtin.rs b/src/libsyntax/attr/builtin.rs
index 958e4373cc0..70f4f47621a 100644
--- a/src/libsyntax/attr/builtin.rs
+++ b/src/libsyntax/attr/builtin.rs
@@ -2,9 +2,8 @@
 
 use super::{mark_used, MetaItemKind};
 use crate::ast::{self, Attribute, MetaItem, NestedMetaItem};
-use crate::feature_gate::feature_err;
 use crate::print::pprust;
-use crate::sess::ParseSess;
+use crate::sess::{feature_err, ParseSess};
 
 use rustc_errors::{struct_span_err, Applicability, Handler};
 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
diff --git a/src/libsyntax/early_buffered_lints.rs b/src/libsyntax/early_buffered_lints.rs
deleted file mode 100644
index 7724107888a..00000000000
--- a/src/libsyntax/early_buffered_lints.rs
+++ /dev/null
@@ -1,30 +0,0 @@
-//! Allows the buffering of lints for later.
-//!
-//! Since we cannot have a dependency on `librustc`, we implement some types here that are somewhat
-//! redundant. Later, these types can be converted to types for use by the rest of the compiler.
-
-use rustc_session::declare_lint;
-pub use rustc_session::lint::BufferedEarlyLint;
-use rustc_session::lint::FutureIncompatibleInfo;
-
-declare_lint! {
-    pub ILL_FORMED_ATTRIBUTE_INPUT,
-    Deny,
-    "ill-formed attribute inputs that were previously accepted and used in practice",
-    @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #57571 <https://github.com/rust-lang/rust/issues/57571>",
-        edition: None,
-    };
-}
-
-declare_lint! {
-    pub META_VARIABLE_MISUSE,
-    Allow,
-    "possible meta-variable misuse at macro definition"
-}
-
-declare_lint! {
-    pub INCOMPLETE_INCLUDE,
-    Deny,
-    "trailing content in included file"
-}
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
deleted file mode 100644
index 4eee4e943c2..00000000000
--- a/src/libsyntax/feature_gate/check.rs
+++ /dev/null
@@ -1,962 +0,0 @@
-use crate::ast::{self, AssocTyConstraint, AssocTyConstraintKind, NodeId};
-use crate::ast::{GenericParam, GenericParamKind, PatKind, RangeEnd, VariantData};
-use crate::attr;
-use crate::sess::ParseSess;
-use crate::visit::{self, FnKind, Visitor};
-
-use rustc_data_structures::fx::FxHashMap;
-use rustc_error_codes::*;
-use rustc_errors::{error_code, struct_span_err, Applicability, DiagnosticBuilder, Handler};
-use rustc_feature::{find_feature_issue, GateIssue};
-use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
-use rustc_feature::{Feature, Features, State as FeatureState, UnstableFeatures};
-use rustc_feature::{
-    ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES,
-};
-use rustc_span::edition::{Edition, ALL_EDITIONS};
-use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{sym, Symbol};
-use rustc_span::{MultiSpan, Span, DUMMY_SP};
-
-use log::debug;
-
-macro_rules! gate_feature_fn {
-    ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
-        let (cx, has_feature, span, name, explain, level) =
-            (&*$cx, $has_feature, $span, $name, $explain, $level);
-        let has_feature: bool = has_feature(&$cx.features);
-        debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
-        if !has_feature && !span.allows_unstable($name) {
-            leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
-                .emit();
-        }
-    }};
-}
-
-macro_rules! gate_feature {
-    ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
-        gate_feature_fn!(
-            $cx,
-            |x: &Features| x.$feature,
-            $span,
-            sym::$feature,
-            $explain,
-            GateStrength::Hard
-        )
-    };
-    ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
-        gate_feature_fn!($cx, |x: &Features| x.$feature, $span, sym::$feature, $explain, $level)
-    };
-}
-
-pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
-    PostExpansionVisitor { parse_sess, features }.visit_attribute(attr)
-}
-
-#[derive(Debug, Copy, Clone, PartialEq)]
-pub enum GateStrength {
-    /// A hard error. (Most feature gates should use this.)
-    Hard,
-    /// Only a warning. (Use this only as backwards-compatibility demands.)
-    Soft,
-}
-
-pub fn feature_err<'a>(
-    sess: &'a ParseSess,
-    feature: Symbol,
-    span: impl Into<MultiSpan>,
-    explain: &str,
-) -> DiagnosticBuilder<'a> {
-    feature_err_issue(sess, feature, span, GateIssue::Language, explain)
-}
-
-pub fn feature_err_issue<'a>(
-    sess: &'a ParseSess,
-    feature: Symbol,
-    span: impl Into<MultiSpan>,
-    issue: GateIssue,
-    explain: &str,
-) -> DiagnosticBuilder<'a> {
-    leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
-}
-
-fn leveled_feature_err<'a>(
-    sess: &'a ParseSess,
-    feature: Symbol,
-    span: impl Into<MultiSpan>,
-    issue: GateIssue,
-    explain: &str,
-    level: GateStrength,
-) -> DiagnosticBuilder<'a> {
-    let diag = &sess.span_diagnostic;
-
-    let mut err = match level {
-        GateStrength::Hard => diag.struct_span_err_with_code(span, explain, error_code!(E0658)),
-        GateStrength::Soft => diag.struct_span_warn(span, explain),
-    };
-
-    if let Some(n) = find_feature_issue(feature, issue) {
-        err.note(&format!(
-            "for more information, see https://github.com/rust-lang/rust/issues/{}",
-            n,
-        ));
-    }
-
-    // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
-    if sess.unstable_features.is_nightly_build() {
-        err.help(&format!("add `#![feature({})]` to the crate attributes to enable", feature));
-    }
-
-    // If we're on stable and only emitting a "soft" warning, add a note to
-    // clarify that the feature isn't "on" (rather than being on but
-    // warning-worthy).
-    if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
-        err.help("a nightly build of the compiler is required to enable this feature");
-    }
-
-    err
-}
-
-struct PostExpansionVisitor<'a> {
-    parse_sess: &'a ParseSess,
-    features: &'a Features,
-}
-
-macro_rules! gate_feature_post {
-    ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
-        let (cx, span) = ($cx, $span);
-        if !span.allows_unstable(sym::$feature) {
-            gate_feature!(cx, $feature, span, $explain)
-        }
-    }};
-    ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
-        let (cx, span) = ($cx, $span);
-        if !span.allows_unstable(sym::$feature) {
-            gate_feature!(cx, $feature, span, $explain, $level)
-        }
-    }};
-}
-
-impl<'a> PostExpansionVisitor<'a> {
-    fn check_abi(&self, abi: ast::StrLit) {
-        let ast::StrLit { symbol_unescaped, span, .. } = abi;
-
-        match &*symbol_unescaped.as_str() {
-            // Stable
-            "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
-            | "system" => {}
-            "rust-intrinsic" => {
-                gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
-            }
-            "platform-intrinsic" => {
-                gate_feature_post!(
-                    &self,
-                    platform_intrinsics,
-                    span,
-                    "platform intrinsics are experimental and possibly buggy"
-                );
-            }
-            "vectorcall" => {
-                gate_feature_post!(
-                    &self,
-                    abi_vectorcall,
-                    span,
-                    "vectorcall is experimental and subject to change"
-                );
-            }
-            "thiscall" => {
-                gate_feature_post!(
-                    &self,
-                    abi_thiscall,
-                    span,
-                    "thiscall is experimental and subject to change"
-                );
-            }
-            "rust-call" => {
-                gate_feature_post!(
-                    &self,
-                    unboxed_closures,
-                    span,
-                    "rust-call ABI is subject to change"
-                );
-            }
-            "ptx-kernel" => {
-                gate_feature_post!(
-                    &self,
-                    abi_ptx,
-                    span,
-                    "PTX ABIs are experimental and subject to change"
-                );
-            }
-            "unadjusted" => {
-                gate_feature_post!(
-                    &self,
-                    abi_unadjusted,
-                    span,
-                    "unadjusted ABI is an implementation detail and perma-unstable"
-                );
-            }
-            "msp430-interrupt" => {
-                gate_feature_post!(
-                    &self,
-                    abi_msp430_interrupt,
-                    span,
-                    "msp430-interrupt ABI is experimental and subject to change"
-                );
-            }
-            "x86-interrupt" => {
-                gate_feature_post!(
-                    &self,
-                    abi_x86_interrupt,
-                    span,
-                    "x86-interrupt ABI is experimental and subject to change"
-                );
-            }
-            "amdgpu-kernel" => {
-                gate_feature_post!(
-                    &self,
-                    abi_amdgpu_kernel,
-                    span,
-                    "amdgpu-kernel ABI is experimental and subject to change"
-                );
-            }
-            "efiapi" => {
-                gate_feature_post!(
-                    &self,
-                    abi_efiapi,
-                    span,
-                    "efiapi ABI is experimental and subject to change"
-                );
-            }
-            abi => self
-                .parse_sess
-                .span_diagnostic
-                .delay_span_bug(span, &format!("unrecognized ABI not caught in lowering: {}", abi)),
-        }
-    }
-
-    fn check_extern(&self, ext: ast::Extern) {
-        if let ast::Extern::Explicit(abi) = ext {
-            self.check_abi(abi);
-        }
-    }
-
-    fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
-        let has_fields = variants.iter().any(|variant| match variant.data {
-            VariantData::Tuple(..) | VariantData::Struct(..) => true,
-            VariantData::Unit(..) => false,
-        });
-
-        let discriminant_spans = variants
-            .iter()
-            .filter(|variant| match variant.data {
-                VariantData::Tuple(..) | VariantData::Struct(..) => false,
-                VariantData::Unit(..) => true,
-            })
-            .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
-            .collect::<Vec<_>>();
-
-        if !discriminant_spans.is_empty() && has_fields {
-            let mut err = feature_err(
-                self.parse_sess,
-                sym::arbitrary_enum_discriminant,
-                discriminant_spans.clone(),
-                "custom discriminant values are not allowed in enums with tuple or struct variants",
-            );
-            for sp in discriminant_spans {
-                err.span_label(sp, "disallowed custom discriminant");
-            }
-            for variant in variants.iter() {
-                match &variant.data {
-                    VariantData::Struct(..) => {
-                        err.span_label(variant.span, "struct variant defined here");
-                    }
-                    VariantData::Tuple(..) => {
-                        err.span_label(variant.span, "tuple variant defined here");
-                    }
-                    VariantData::Unit(..) => {}
-                }
-            }
-            err.emit();
-        }
-    }
-
-    fn check_gat(&self, generics: &ast::Generics, span: Span) {
-        if !generics.params.is_empty() {
-            gate_feature_post!(
-                &self,
-                generic_associated_types,
-                span,
-                "generic associated types are unstable"
-            );
-        }
-        if !generics.where_clause.predicates.is_empty() {
-            gate_feature_post!(
-                &self,
-                generic_associated_types,
-                span,
-                "where clauses on associated types are unstable"
-            );
-        }
-    }
-
-    /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
-    fn check_impl_trait(&self, ty: &ast::Ty) {
-        struct ImplTraitVisitor<'a> {
-            vis: &'a PostExpansionVisitor<'a>,
-        }
-        impl Visitor<'_> for ImplTraitVisitor<'_> {
-            fn visit_ty(&mut self, ty: &ast::Ty) {
-                if let ast::TyKind::ImplTrait(..) = ty.kind {
-                    gate_feature_post!(
-                        &self.vis,
-                        type_alias_impl_trait,
-                        ty.span,
-                        "`impl Trait` in type aliases is unstable"
-                    );
-                }
-                visit::walk_ty(self, ty);
-            }
-        }
-        ImplTraitVisitor { vis: self }.visit_ty(ty);
-    }
-}
-
-impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
-    fn visit_attribute(&mut self, attr: &ast::Attribute) {
-        let attr_info =
-            attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
-        // Check feature gates for built-in attributes.
-        if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
-            gate_feature_fn!(self, has_feature, attr.span, name, descr, GateStrength::Hard);
-        }
-        // Check unstable flavors of the `#[doc]` attribute.
-        if attr.check_name(sym::doc) {
-            for nested_meta in attr.meta_item_list().unwrap_or_default() {
-                macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
-                    $(if nested_meta.check_name(sym::$name) {
-                        let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
-                        gate_feature!(self, $feature, attr.span, msg);
-                    })*
-                }}
-
-                gate_doc!(
-                    include => external_doc
-                    cfg => doc_cfg
-                    masked => doc_masked
-                    spotlight => doc_spotlight
-                    alias => doc_alias
-                    keyword => doc_keyword
-                );
-            }
-        }
-    }
-
-    fn visit_name(&mut self, sp: Span, name: ast::Name) {
-        if !name.as_str().is_ascii() {
-            gate_feature_post!(
-                &self,
-                non_ascii_idents,
-                self.parse_sess.source_map().def_span(sp),
-                "non-ascii idents are not fully supported"
-            );
-        }
-    }
-
-    fn visit_item(&mut self, i: &'a ast::Item) {
-        match i.kind {
-            ast::ItemKind::ForeignMod(ref foreign_module) => {
-                if let Some(abi) = foreign_module.abi {
-                    self.check_abi(abi);
-                }
-            }
-
-            ast::ItemKind::Fn(..) => {
-                if attr::contains_name(&i.attrs[..], sym::plugin_registrar) {
-                    gate_feature_post!(
-                        &self,
-                        plugin_registrar,
-                        i.span,
-                        "compiler plugins are experimental and possibly buggy"
-                    );
-                }
-                if attr::contains_name(&i.attrs[..], sym::start) {
-                    gate_feature_post!(
-                        &self,
-                        start,
-                        i.span,
-                        "`#[start]` functions are experimental \
-                                       and their signature may change \
-                                       over time"
-                    );
-                }
-                if attr::contains_name(&i.attrs[..], sym::main) {
-                    gate_feature_post!(
-                        &self,
-                        main,
-                        i.span,
-                        "declaration of a non-standard `#[main]` \
-                                        function may change over time, for now \
-                                        a top-level `fn main()` is required"
-                    );
-                }
-            }
-
-            ast::ItemKind::Struct(..) => {
-                for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
-                    for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
-                        if item.check_name(sym::simd) {
-                            gate_feature_post!(
-                                &self,
-                                repr_simd,
-                                attr.span,
-                                "SIMD types are experimental and possibly buggy"
-                            );
-                        }
-                    }
-                }
-            }
-
-            ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
-                for variant in variants {
-                    match (&variant.data, &variant.disr_expr) {
-                        (ast::VariantData::Unit(..), _) => {}
-                        (_, Some(disr_expr)) => gate_feature_post!(
-                            &self,
-                            arbitrary_enum_discriminant,
-                            disr_expr.value.span,
-                            "discriminants on non-unit variants are experimental"
-                        ),
-                        _ => {}
-                    }
-                }
-
-                let has_feature = self.features.arbitrary_enum_discriminant;
-                if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
-                    self.maybe_report_invalid_custom_discriminants(&variants);
-                }
-            }
-
-            ast::ItemKind::Impl(_, polarity, defaultness, ..) => {
-                if polarity == ast::ImplPolarity::Negative {
-                    gate_feature_post!(
-                        &self,
-                        optin_builtin_traits,
-                        i.span,
-                        "negative trait bounds are not yet fully implemented; \
-                                        use marker types for now"
-                    );
-                }
-
-                if let ast::Defaultness::Default = defaultness {
-                    gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
-                }
-            }
-
-            ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
-                gate_feature_post!(
-                    &self,
-                    optin_builtin_traits,
-                    i.span,
-                    "auto traits are experimental and possibly buggy"
-                );
-            }
-
-            ast::ItemKind::TraitAlias(..) => {
-                gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
-            }
-
-            ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
-                let msg = "`macro` is experimental";
-                gate_feature_post!(&self, decl_macro, i.span, msg);
-            }
-
-            ast::ItemKind::TyAlias(ref ty, ..) => self.check_impl_trait(&ty),
-
-            _ => {}
-        }
-
-        visit::walk_item(self, i);
-    }
-
-    fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
-        match i.kind {
-            ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
-                let link_name = attr::first_attr_value_str_by_name(&i.attrs, sym::link_name);
-                let links_to_llvm = match link_name {
-                    Some(val) => val.as_str().starts_with("llvm."),
-                    _ => false,
-                };
-                if links_to_llvm {
-                    gate_feature_post!(
-                        &self,
-                        link_llvm_intrinsics,
-                        i.span,
-                        "linking to LLVM intrinsics is experimental"
-                    );
-                }
-            }
-            ast::ForeignItemKind::Ty => {
-                gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
-            }
-            ast::ForeignItemKind::Macro(..) => {}
-        }
-
-        visit::walk_foreign_item(self, i)
-    }
-
-    fn visit_ty(&mut self, ty: &'a ast::Ty) {
-        match ty.kind {
-            ast::TyKind::BareFn(ref bare_fn_ty) => {
-                self.check_extern(bare_fn_ty.ext);
-            }
-            ast::TyKind::Never => {
-                gate_feature_post!(&self, never_type, ty.span, "The `!` type is experimental");
-            }
-            _ => {}
-        }
-        visit::walk_ty(self, ty)
-    }
-
-    fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
-        if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
-            if let ast::TyKind::Never = output_ty.kind {
-                // Do nothing.
-            } else {
-                self.visit_ty(output_ty)
-            }
-        }
-    }
-
-    fn visit_expr(&mut self, e: &'a ast::Expr) {
-        match e.kind {
-            ast::ExprKind::Box(_) => {
-                gate_feature_post!(
-                    &self,
-                    box_syntax,
-                    e.span,
-                    "box expression syntax is experimental; you can call `Box::new` instead"
-                );
-            }
-            ast::ExprKind::Type(..) => {
-                // To avoid noise about type ascription in common syntax errors, only emit if it
-                // is the *only* error.
-                if self.parse_sess.span_diagnostic.err_count() == 0 {
-                    gate_feature_post!(
-                        &self,
-                        type_ascription,
-                        e.span,
-                        "type ascription is experimental"
-                    );
-                }
-            }
-            ast::ExprKind::TryBlock(_) => {
-                gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
-            }
-            ast::ExprKind::Block(_, opt_label) => {
-                if let Some(label) = opt_label {
-                    gate_feature_post!(
-                        &self,
-                        label_break_value,
-                        label.ident.span,
-                        "labels on blocks are unstable"
-                    );
-                }
-            }
-            _ => {}
-        }
-        visit::walk_expr(self, e)
-    }
-
-    fn visit_arm(&mut self, arm: &'a ast::Arm) {
-        visit::walk_arm(self, arm)
-    }
-
-    fn visit_pat(&mut self, pattern: &'a ast::Pat) {
-        match &pattern.kind {
-            PatKind::Slice(pats) => {
-                for pat in &*pats {
-                    let span = pat.span;
-                    let inner_pat = match &pat.kind {
-                        PatKind::Ident(.., Some(pat)) => pat,
-                        _ => pat,
-                    };
-                    if inner_pat.is_rest() {
-                        gate_feature_post!(
-                            &self,
-                            slice_patterns,
-                            span,
-                            "subslice patterns are unstable"
-                        );
-                    }
-                }
-            }
-            PatKind::Box(..) => {
-                gate_feature_post!(
-                    &self,
-                    box_patterns,
-                    pattern.span,
-                    "box pattern syntax is experimental"
-                );
-            }
-            PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
-                gate_feature_post!(
-                    &self,
-                    exclusive_range_pattern,
-                    pattern.span,
-                    "exclusive range pattern syntax is experimental"
-                );
-            }
-            _ => {}
-        }
-        visit::walk_pat(self, pattern)
-    }
-
-    fn visit_fn(
-        &mut self,
-        fn_kind: FnKind<'a>,
-        fn_decl: &'a ast::FnDecl,
-        span: Span,
-        _node_id: NodeId,
-    ) {
-        if let Some(header) = fn_kind.header() {
-            // Stability of const fn methods are covered in
-            // `visit_trait_item` and `visit_impl_item` below; this is
-            // because default methods don't pass through this point.
-            self.check_extern(header.ext);
-        }
-
-        if fn_decl.c_variadic() {
-            gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
-        }
-
-        visit::walk_fn(self, fn_kind, fn_decl, span)
-    }
-
-    fn visit_generic_param(&mut self, param: &'a GenericParam) {
-        match param.kind {
-            GenericParamKind::Const { .. } => gate_feature_post!(
-                &self,
-                const_generics,
-                param.ident.span,
-                "const generics are unstable"
-            ),
-            _ => {}
-        }
-        visit::walk_generic_param(self, param)
-    }
-
-    fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
-        match constraint.kind {
-            AssocTyConstraintKind::Bound { .. } => gate_feature_post!(
-                &self,
-                associated_type_bounds,
-                constraint.span,
-                "associated type bounds are unstable"
-            ),
-            _ => {}
-        }
-        visit::walk_assoc_ty_constraint(self, constraint)
-    }
-
-    fn visit_trait_item(&mut self, ti: &'a ast::AssocItem) {
-        match ti.kind {
-            ast::AssocItemKind::Fn(ref sig, ref block) => {
-                if block.is_none() {
-                    self.check_extern(sig.header.ext);
-                }
-                if sig.header.constness.node == ast::Constness::Const {
-                    gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
-                }
-            }
-            ast::AssocItemKind::TyAlias(_, ref default) => {
-                if let Some(_) = default {
-                    gate_feature_post!(
-                        &self,
-                        associated_type_defaults,
-                        ti.span,
-                        "associated type defaults are unstable"
-                    );
-                }
-            }
-            _ => {}
-        }
-        visit::walk_trait_item(self, ti)
-    }
-
-    fn visit_assoc_item(&mut self, ii: &'a ast::AssocItem) {
-        if ii.defaultness == ast::Defaultness::Default {
-            gate_feature_post!(&self, specialization, ii.span, "specialization is unstable");
-        }
-
-        match ii.kind {
-            ast::AssocItemKind::Fn(ref sig, _) => {
-                if sig.decl.c_variadic() {
-                    gate_feature_post!(
-                        &self,
-                        c_variadic,
-                        ii.span,
-                        "C-variadic functions are unstable"
-                    );
-                }
-            }
-            ast::AssocItemKind::TyAlias(_, ref ty) => {
-                if let Some(ty) = ty {
-                    self.check_impl_trait(ty);
-                }
-                self.check_gat(&ii.generics, ii.span);
-            }
-            _ => {}
-        }
-        visit::walk_assoc_item(self, ii)
-    }
-
-    fn visit_vis(&mut self, vis: &'a ast::Visibility) {
-        if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
-            gate_feature_post!(
-                &self,
-                crate_visibility_modifier,
-                vis.span,
-                "`crate` visibility modifier is experimental"
-            );
-        }
-        visit::walk_vis(self, vis)
-    }
-}
-
-pub fn get_features(
-    span_handler: &Handler,
-    krate_attrs: &[ast::Attribute],
-    crate_edition: Edition,
-    allow_features: &Option<Vec<String>>,
-) -> Features {
-    fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
-        let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
-        err.span_label(span, "feature has been removed");
-        if let Some(reason) = reason {
-            err.note(reason);
-        }
-        err.emit();
-    }
-
-    let mut features = Features::default();
-    let mut edition_enabled_features = FxHashMap::default();
-
-    for &edition in ALL_EDITIONS {
-        if edition <= crate_edition {
-            // The `crate_edition` implies its respective umbrella feature-gate
-            // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
-            edition_enabled_features.insert(edition.feature_name(), edition);
-        }
-    }
-
-    for feature in active_features_up_to(crate_edition) {
-        feature.set(&mut features, DUMMY_SP);
-        edition_enabled_features.insert(feature.name, crate_edition);
-    }
-
-    // Process the edition umbrella feature-gates first, to ensure
-    // `edition_enabled_features` is completed before it's queried.
-    for attr in krate_attrs {
-        if !attr.check_name(sym::feature) {
-            continue;
-        }
-
-        let list = match attr.meta_item_list() {
-            Some(list) => list,
-            None => continue,
-        };
-
-        for mi in list {
-            if !mi.is_word() {
-                continue;
-            }
-
-            let name = mi.name_or_empty();
-
-            let edition = ALL_EDITIONS.iter().find(|e| name == e.feature_name()).copied();
-            if let Some(edition) = edition {
-                if edition <= crate_edition {
-                    continue;
-                }
-
-                for feature in active_features_up_to(edition) {
-                    // FIXME(Manishearth) there is currently no way to set
-                    // lib features by edition
-                    feature.set(&mut features, DUMMY_SP);
-                    edition_enabled_features.insert(feature.name, edition);
-                }
-            }
-        }
-    }
-
-    for attr in krate_attrs {
-        if !attr.check_name(sym::feature) {
-            continue;
-        }
-
-        let list = match attr.meta_item_list() {
-            Some(list) => list,
-            None => continue,
-        };
-
-        let bad_input = |span| {
-            struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
-        };
-
-        for mi in list {
-            let name = match mi.ident() {
-                Some(ident) if mi.is_word() => ident.name,
-                Some(ident) => {
-                    bad_input(mi.span())
-                        .span_suggestion(
-                            mi.span(),
-                            "expected just one word",
-                            format!("{}", ident.name),
-                            Applicability::MaybeIncorrect,
-                        )
-                        .emit();
-                    continue;
-                }
-                None => {
-                    bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
-                    continue;
-                }
-            };
-
-            if let Some(edition) = edition_enabled_features.get(&name) {
-                let msg =
-                    &format!("the feature `{}` is included in the Rust {} edition", name, edition);
-                span_handler.struct_span_warn_with_code(mi.span(), msg, error_code!(E0705)).emit();
-                continue;
-            }
-
-            if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
-                // Handled in the separate loop above.
-                continue;
-            }
-
-            let removed = REMOVED_FEATURES.iter().find(|f| name == f.name);
-            let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.name);
-            if let Some(Feature { state, .. }) = removed.or(stable_removed) {
-                if let FeatureState::Removed { reason } | FeatureState::Stabilized { reason } =
-                    state
-                {
-                    feature_removed(span_handler, mi.span(), *reason);
-                    continue;
-                }
-            }
-
-            if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
-                let since = Some(Symbol::intern(since));
-                features.declared_lang_features.push((name, mi.span(), since));
-                continue;
-            }
-
-            if let Some(allowed) = allow_features.as_ref() {
-                if allowed.iter().find(|&f| name.as_str() == *f).is_none() {
-                    struct_span_err!(
-                        span_handler,
-                        mi.span(),
-                        E0725,
-                        "the feature `{}` is not in the list of allowed features",
-                        name
-                    )
-                    .emit();
-                    continue;
-                }
-            }
-
-            if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.name) {
-                f.set(&mut features, mi.span());
-                features.declared_lang_features.push((name, mi.span(), None));
-                continue;
-            }
-
-            features.declared_lib_features.push((name, mi.span()));
-        }
-    }
-
-    features
-}
-
-fn active_features_up_to(edition: Edition) -> impl Iterator<Item = &'static Feature> {
-    ACTIVE_FEATURES.iter().filter(move |feature| {
-        if let Some(feature_edition) = feature.edition { feature_edition <= edition } else { false }
-    })
-}
-
-pub fn check_crate(
-    krate: &ast::Crate,
-    parse_sess: &ParseSess,
-    features: &Features,
-    unstable: UnstableFeatures,
-) {
-    maybe_stage_features(&parse_sess.span_diagnostic, krate, unstable);
-    let mut visitor = PostExpansionVisitor { parse_sess, features };
-
-    let spans = parse_sess.gated_spans.spans.borrow();
-    macro_rules! gate_all {
-        ($gate:ident, $msg:literal) => {
-            for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
-                gate_feature!(&visitor, $gate, *span, $msg);
-            }
-        };
-    }
-    gate_all!(let_chains, "`let` expressions in this position are experimental");
-    gate_all!(async_closure, "async closures are unstable");
-    gate_all!(generators, "yield syntax is experimental");
-    gate_all!(or_patterns, "or-patterns syntax is experimental");
-    gate_all!(const_extern_fn, "`const extern fn` definitions are unstable");
-    gate_all!(raw_ref_op, "raw address of syntax is experimental");
-    gate_all!(const_trait_bound_opt_out, "`?const` on trait bounds is experimental");
-    gate_all!(const_trait_impl, "const trait impls are experimental");
-    gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
-
-    // All uses of `gate_all!` below this point were added in #65742,
-    // and subsequently disabled (with the non-early gating readded).
-    macro_rules! gate_all {
-        ($gate:ident, $msg:literal) => {
-            // FIXME(eddyb) do something more useful than always
-            // disabling these uses of early feature-gatings.
-            if false {
-                for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
-                    gate_feature!(&visitor, $gate, *span, $msg);
-                }
-            }
-        };
-    }
-
-    gate_all!(trait_alias, "trait aliases are experimental");
-    gate_all!(associated_type_bounds, "associated type bounds are unstable");
-    gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
-    gate_all!(const_generics, "const generics are unstable");
-    gate_all!(decl_macro, "`macro` is experimental");
-    gate_all!(box_patterns, "box pattern syntax is experimental");
-    gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
-    gate_all!(try_blocks, "`try` blocks are unstable");
-    gate_all!(label_break_value, "labels on blocks are unstable");
-    gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
-    // To avoid noise about type ascription in common syntax errors,
-    // only emit if it is the *only* error. (Also check it last.)
-    if parse_sess.span_diagnostic.err_count() == 0 {
-        gate_all!(type_ascription, "type ascription is experimental");
-    }
-
-    visit::walk_crate(&mut visitor, krate);
-}
-
-fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate, unstable: UnstableFeatures) {
-    if !unstable.is_nightly_build() {
-        for attr in krate.attrs.iter().filter(|attr| attr.check_name(sym::feature)) {
-            struct_span_err!(
-                span_handler,
-                attr.span,
-                E0554,
-                "`#![feature]` may not be used on the {} release channel",
-                option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
-            )
-            .emit();
-        }
-    }
-}
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 7ee4ca4603c..a96fee0cf8f 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -75,13 +75,8 @@ pub mod ast;
 pub mod attr;
 pub mod entry;
 pub mod expand;
-pub mod feature_gate {
-    mod check;
-    pub use check::{check_attribute, check_crate, feature_err, feature_err_issue, get_features};
-}
 pub mod mut_visit;
 pub mod ptr;
-pub mod show_span;
 pub use rustc_session::parse as sess;
 pub mod token;
 pub mod tokenstream;
@@ -93,8 +88,6 @@ pub mod print {
     pub mod pprust;
 }
 
-pub mod early_buffered_lints;
-
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
diff --git a/src/libsyntax/show_span.rs b/src/libsyntax/show_span.rs
deleted file mode 100644
index b70e2ce0d3e..00000000000
--- a/src/libsyntax/show_span.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-//! Span debugger
-//!
-//! This module shows spans for all expressions in the crate
-//! to help with compiler debugging.
-
-use std::str::FromStr;
-
-use crate::ast;
-use crate::visit;
-use crate::visit::Visitor;
-
-enum Mode {
-    Expression,
-    Pattern,
-    Type,
-}
-
-impl FromStr for Mode {
-    type Err = ();
-    fn from_str(s: &str) -> Result<Mode, ()> {
-        let mode = match s {
-            "expr" => Mode::Expression,
-            "pat" => Mode::Pattern,
-            "ty" => Mode::Type,
-            _ => return Err(()),
-        };
-        Ok(mode)
-    }
-}
-
-struct ShowSpanVisitor<'a> {
-    span_diagnostic: &'a rustc_errors::Handler,
-    mode: Mode,
-}
-
-impl<'a> Visitor<'a> for ShowSpanVisitor<'a> {
-    fn visit_expr(&mut self, e: &'a ast::Expr) {
-        if let Mode::Expression = self.mode {
-            self.span_diagnostic.span_warn(e.span, "expression");
-        }
-        visit::walk_expr(self, e);
-    }
-
-    fn visit_pat(&mut self, p: &'a ast::Pat) {
-        if let Mode::Pattern = self.mode {
-            self.span_diagnostic.span_warn(p.span, "pattern");
-        }
-        visit::walk_pat(self, p);
-    }
-
-    fn visit_ty(&mut self, t: &'a ast::Ty) {
-        if let Mode::Type = self.mode {
-            self.span_diagnostic.span_warn(t.span, "type");
-        }
-        visit::walk_ty(self, t);
-    }
-
-    fn visit_mac(&mut self, mac: &'a ast::Mac) {
-        visit::walk_mac(self, mac);
-    }
-}
-
-pub fn run(span_diagnostic: &rustc_errors::Handler, mode: &str, krate: &ast::Crate) {
-    let mode = match mode.parse().ok() {
-        Some(mode) => mode,
-        None => return,
-    };
-    let mut v = ShowSpanVisitor { span_diagnostic, mode };
-    visit::walk_crate(&mut v, krate);
-}