Remove polymorphization

6 files changed, 10 insertions, 380 deletions

diff --git a/compiler/rustc_monomorphize/messages.ftl b/compiler/rustc_monomorphize/messages.ftl
index 8528a2e68c0..540ce7cc4ce 100644
--- a/compiler/rustc_monomorphize/messages.ftl
+++ b/compiler/rustc_monomorphize/messages.ftl
@@ -41,6 +41,4 @@ monomorphize_symbol_already_defined = symbol `{$symbol}` is already defined
 monomorphize_unknown_cgu_collection_mode =
     unknown codegen-item collection mode '{$mode}', falling back to 'lazy' mode
 
-monomorphize_unused_generic_params = item has unused generic parameters
-
 monomorphize_written_to_path = the full type name has been written to '{$path}'
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 5efe7ffc7b9..480d82c1a38 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -965,9 +965,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -
         return true;
     }
 
-    if tcx.is_reachable_non_generic(def_id)
-        || instance.polymorphize(*tcx).upstream_monomorphization(*tcx).is_some()
-    {
+    if tcx.is_reachable_non_generic(def_id) || instance.upstream_monomorphization(*tcx).is_some() {
         // We can link to the item in question, no instance needed in this crate.
         return false;
     }
@@ -1114,7 +1112,7 @@ fn create_fn_mono_item<'tcx>(
         crate::util::dump_closure_profile(tcx, instance);
     }
 
-    respan(source, MonoItem::Fn(instance.polymorphize(tcx)))
+    respan(source, MonoItem::Fn(instance))
 }
 
 /// Creates a `MonoItem` for each method that is referenced by the vtable for
diff --git a/compiler/rustc_monomorphize/src/errors.rs b/compiler/rustc_monomorphize/src/errors.rs
index 02865cad302..fc8d63b5888 100644
--- a/compiler/rustc_monomorphize/src/errors.rs
+++ b/compiler/rustc_monomorphize/src/errors.rs
@@ -1,11 +1,8 @@
 use std::path::PathBuf;
 
-use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, LintDiagnostic};
 use rustc_span::{Span, Symbol};
 
-use crate::fluent_generated as fluent;
-
 #[derive(Diagnostic)]
 #[diag(monomorphize_recursion_limit)]
 pub(crate) struct RecursionLimit {
@@ -28,28 +25,6 @@ pub(crate) struct NoOptimizedMir {
     pub crate_name: Symbol,
 }
 
-pub(crate) struct UnusedGenericParamsHint {
-    pub span: Span,
-    pub param_spans: Vec<Span>,
-    pub param_names: Vec<String>,
-}
-
-impl<G: EmissionGuarantee> Diagnostic<'_, G> for UnusedGenericParamsHint {
-    #[track_caller]
-    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
-        let mut diag = Diag::new(dcx, level, fluent::monomorphize_unused_generic_params);
-        diag.span(self.span);
-        for (span, name) in self.param_spans.into_iter().zip(self.param_names) {
-            // FIXME: I can figure out how to do a label with a fluent string with a fixed message,
-            // or a label with a dynamic value in a hard-coded string, but I haven't figured out
-            // how to combine the two. 😢
-            #[allow(rustc::untranslatable_diagnostic)]
-            diag.span_label(span, format!("generic parameter `{name}` is unused"));
-        }
-        diag
-    }
-}
-
 #[derive(LintDiagnostic)]
 #[diag(monomorphize_large_assignments)]
 #[note]
diff --git a/compiler/rustc_monomorphize/src/lib.rs b/compiler/rustc_monomorphize/src/lib.rs
index 0f08930fb4c..caae54cd559 100644
--- a/compiler/rustc_monomorphize/src/lib.rs
+++ b/compiler/rustc_monomorphize/src/lib.rs
@@ -19,7 +19,6 @@ mod collector;
 mod errors;
 mod mono_checks;
 mod partitioning;
-mod polymorphize;
 mod util;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
@@ -50,6 +49,5 @@ fn custom_coerce_unsize_info<'tcx>(
 
 pub fn provide(providers: &mut Providers) {
     partitioning::provide(providers);
-    polymorphize::provide(providers);
     mono_checks::provide(providers);
 }
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index 7ea4ded2b05..dabce72650a 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -113,7 +113,6 @@ use rustc_middle::mir::mono::{
     Visibility,
 };
 use rustc_middle::ty::print::{characteristic_def_id_of_type, with_no_trimmed_paths};
-use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, InstanceKind, TyCtxt};
 use rustc_middle::util::Providers;
 use rustc_session::CodegenUnits;
@@ -661,18 +660,14 @@ fn characteristic_def_id_of_mono_item<'tcx>(
                     return None;
                 }
 
-                // When polymorphization is enabled, methods which do not depend on their generic
-                // parameters, but the self-type of their impl block do will fail to normalize.
-                if !tcx.sess.opts.unstable_opts.polymorphize || !instance.has_param() {
-                    // This is a method within an impl, find out what the self-type is:
-                    let impl_self_ty = tcx.instantiate_and_normalize_erasing_regions(
-                        instance.args,
-                        ty::TypingEnv::fully_monomorphized(),
-                        tcx.type_of(impl_def_id),
-                    );
-                    if let Some(def_id) = characteristic_def_id_of_type(impl_self_ty) {
-                        return Some(def_id);
-                    }
+                // This is a method within an impl, find out what the self-type is:
+                let impl_self_ty = tcx.instantiate_and_normalize_erasing_regions(
+                    instance.args,
+                    ty::TypingEnv::fully_monomorphized(),
+                    tcx.type_of(impl_def_id),
+                );
+                if let Some(def_id) = characteristic_def_id_of_type(impl_self_ty) {
+                    return Some(def_id);
                 }
             }
 
diff --git a/compiler/rustc_monomorphize/src/polymorphize.rs b/compiler/rustc_monomorphize/src/polymorphize.rs
deleted file mode 100644
index e049fe99664..00000000000
--- a/compiler/rustc_monomorphize/src/polymorphize.rs
+++ /dev/null
@@ -1,334 +0,0 @@
-//! Polymorphization Analysis
-//! =========================
-//!
-//! This module implements an analysis of functions, methods and closures to determine which
-//! generic parameters are unused (and eventually, in what ways generic parameters are used - only
-//! for their size, offset of a field, etc.).
-
-use rustc_hir::ConstContext;
-use rustc_hir::def::DefKind;
-use rustc_hir::def_id::DefId;
-use rustc_middle::mir::visit::{TyContext, Visitor};
-use rustc_middle::mir::{self, Local, LocalDecl, Location};
-use rustc_middle::query::Providers;
-use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
-use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, UnusedGenericParams};
-use rustc_span::symbol::sym;
-use tracing::{debug, instrument};
-
-use crate::errors::UnusedGenericParamsHint;
-
-/// Provide implementations of queries relating to polymorphization analysis.
-pub(crate) fn provide(providers: &mut Providers) {
-    providers.unused_generic_params = unused_generic_params;
-}
-
-/// Determine which generic parameters are used by the instance.
-///
-/// Returns a bitset where bits representing unused parameters are set (`is_empty` indicates all
-/// parameters are used).
-fn unused_generic_params<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    instance: ty::InstanceKind<'tcx>,
-) -> UnusedGenericParams {
-    assert!(instance.def_id().is_local());
-
-    if !tcx.sess.opts.unstable_opts.polymorphize {
-        // If polymorphization disabled, then all parameters are used.
-        return UnusedGenericParams::new_all_used();
-    }
-
-    let def_id = instance.def_id();
-    // Exit early if this instance should not be polymorphized.
-    if !should_polymorphize(tcx, def_id, instance) {
-        return UnusedGenericParams::new_all_used();
-    }
-
-    let generics = tcx.generics_of(def_id);
-    debug!(?generics);
-
-    // Exit early when there are no parameters to be unused.
-    if generics.is_empty() {
-        return UnusedGenericParams::new_all_used();
-    }
-
-    // Create a bitset with N rightmost ones for each parameter.
-    let generics_count: u32 =
-        generics.count().try_into().expect("more generic parameters than can fit into a `u32`");
-    let mut unused_parameters = UnusedGenericParams::new_all_unused(generics_count);
-    debug!(?unused_parameters, "(start)");
-
-    mark_used_by_default_parameters(tcx, def_id, generics, &mut unused_parameters);
-    debug!(?unused_parameters, "(after default)");
-
-    // Visit MIR and accumulate used generic parameters.
-    let body = match tcx.hir().body_const_context(def_id.expect_local()) {
-        // Const functions are actually called and should thus be considered for polymorphization
-        // via their runtime MIR.
-        Some(ConstContext::ConstFn) | None => tcx.optimized_mir(def_id),
-        Some(_) => tcx.mir_for_ctfe(def_id),
-    };
-    let mut vis = MarkUsedGenericParams { tcx, def_id, unused_parameters: &mut unused_parameters };
-    vis.visit_body(body);
-    debug!(?unused_parameters, "(end)");
-
-    // Emit errors for debugging and testing if enabled.
-    if !unused_parameters.all_used() {
-        emit_unused_generic_params_error(tcx, def_id, generics, &unused_parameters);
-    }
-
-    unused_parameters
-}
-
-/// Returns `true` if the instance should be polymorphized.
-fn should_polymorphize<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    def_id: DefId,
-    instance: ty::InstanceKind<'tcx>,
-) -> bool {
-    // If an instance's MIR body is not polymorphic then the modified generic parameters that are
-    // derived from polymorphization's result won't make any difference.
-    if !instance.has_polymorphic_mir_body() {
-        return false;
-    }
-
-    // Don't polymorphize intrinsics or virtual calls - calling `instance_mir` will panic.
-    if matches!(instance, ty::InstanceKind::Intrinsic(..) | ty::InstanceKind::Virtual(..)) {
-        return false;
-    }
-
-    // Foreign items have no bodies to analyze.
-    if tcx.is_foreign_item(def_id) {
-        return false;
-    }
-
-    // Make sure there is MIR available.
-    match tcx.hir().body_const_context(def_id.expect_local()) {
-        Some(ConstContext::ConstFn) | None if !tcx.is_mir_available(def_id) => {
-            debug!("no mir available");
-            return false;
-        }
-        Some(_) if !tcx.is_ctfe_mir_available(def_id) => {
-            debug!("no ctfe mir available");
-            return false;
-        }
-        _ => true,
-    }
-}
-
-/// Some parameters are considered used-by-default, such as non-generic parameters and the dummy
-/// generic parameters from closures, this function marks them as used. `leaf_is_closure` should
-/// be `true` if the item that `unused_generic_params` was invoked on is a closure.
-#[instrument(level = "debug", skip(tcx, def_id, generics, unused_parameters))]
-fn mark_used_by_default_parameters<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    def_id: DefId,
-    generics: &'tcx ty::Generics,
-    unused_parameters: &mut UnusedGenericParams,
-) {
-    match tcx.def_kind(def_id) {
-        DefKind::Closure | DefKind::SyntheticCoroutineBody => {
-            for param in &generics.own_params {
-                debug!(?param, "(closure/gen)");
-                unused_parameters.mark_used(param.index);
-            }
-        }
-        DefKind::Mod
-        | DefKind::Struct
-        | DefKind::Union
-        | DefKind::Enum
-        | DefKind::Variant
-        | DefKind::Trait
-        | DefKind::TyAlias
-        | DefKind::ForeignTy
-        | DefKind::TraitAlias
-        | DefKind::AssocTy
-        | DefKind::TyParam
-        | DefKind::Fn
-        | DefKind::Const
-        | DefKind::ConstParam
-        | DefKind::Static { .. }
-        | DefKind::Ctor(_, _)
-        | DefKind::AssocFn
-        | DefKind::AssocConst
-        | DefKind::Macro(_)
-        | DefKind::ExternCrate
-        | DefKind::Use
-        | DefKind::ForeignMod
-        | DefKind::AnonConst
-        | DefKind::InlineConst
-        | DefKind::OpaqueTy
-        | DefKind::Field
-        | DefKind::LifetimeParam
-        | DefKind::GlobalAsm
-        | DefKind::Impl { .. } => {
-            for param in &generics.own_params {
-                debug!(?param, "(other)");
-                if let ty::GenericParamDefKind::Lifetime = param.kind {
-                    unused_parameters.mark_used(param.index);
-                }
-            }
-        }
-    }
-
-    if let Some(parent) = generics.parent {
-        mark_used_by_default_parameters(tcx, parent, tcx.generics_of(parent), unused_parameters);
-    }
-}
-
-/// Emit errors for the function annotated by `#[rustc_polymorphize_error]`, labelling each generic
-/// parameter which was unused.
-#[instrument(level = "debug", skip(tcx, generics))]
-fn emit_unused_generic_params_error<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    def_id: DefId,
-    generics: &'tcx ty::Generics,
-    unused_parameters: &UnusedGenericParams,
-) {
-    let base_def_id = tcx.typeck_root_def_id(def_id);
-    if !tcx.has_attr(base_def_id, sym::rustc_polymorphize_error) {
-        return;
-    }
-
-    let fn_span = match tcx.opt_item_ident(def_id) {
-        Some(ident) => ident.span,
-        _ => tcx.def_span(def_id),
-    };
-
-    let mut param_spans = Vec::new();
-    let mut param_names = Vec::new();
-    let mut next_generics = Some(generics);
-    while let Some(generics) = next_generics {
-        for param in &generics.own_params {
-            if unused_parameters.is_unused(param.index) {
-                debug!(?param);
-                let def_span = tcx.def_span(param.def_id);
-                param_spans.push(def_span);
-                param_names.push(param.name.to_string());
-            }
-        }
-
-        next_generics = generics.parent.map(|did| tcx.generics_of(did));
-    }
-
-    tcx.dcx().emit_err(UnusedGenericParamsHint { span: fn_span, param_spans, param_names });
-}
-
-/// Visitor used to aggregate generic parameter uses.
-struct MarkUsedGenericParams<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    def_id: DefId,
-    unused_parameters: &'a mut UnusedGenericParams,
-}
-
-impl<'a, 'tcx> MarkUsedGenericParams<'a, 'tcx> {
-    /// Invoke `unused_generic_params` on a body contained within the current item (e.g.
-    /// a closure, coroutine or constant).
-    #[instrument(level = "debug", skip(self, def_id, args))]
-    fn visit_child_body(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) {
-        let instance = ty::InstanceKind::Item(def_id);
-        let unused = self.tcx.unused_generic_params(instance);
-        debug!(?self.unused_parameters, ?unused);
-        for (i, arg) in args.iter().enumerate() {
-            let i = i.try_into().unwrap();
-            if unused.is_used(i) {
-                arg.visit_with(self);
-            }
-        }
-        debug!(?self.unused_parameters);
-    }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for MarkUsedGenericParams<'a, 'tcx> {
-    #[instrument(level = "debug", skip(self, local))]
-    fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
-        if local == Local::from_usize(1) {
-            let def_kind = self.tcx.def_kind(self.def_id);
-            if matches!(def_kind, DefKind::Closure) {
-                // Skip visiting the closure/coroutine that is currently being processed. This only
-                // happens because the first argument to the closure is a reference to itself and
-                // that will call `visit_args`, resulting in each generic parameter captured being
-                // considered used by default.
-                debug!("skipping closure args");
-                return;
-            }
-        }
-
-        self.super_local_decl(local, local_decl);
-    }
-
-    fn visit_const_operand(&mut self, ct: &mir::ConstOperand<'tcx>, location: Location) {
-        match ct.const_ {
-            mir::Const::Ty(_, c) => {
-                c.visit_with(self);
-            }
-            mir::Const::Unevaluated(mir::UnevaluatedConst { def, args: _, promoted }, ty) => {
-                // Avoid considering `T` unused when constants are of the form:
-                //   `<Self as Foo<T>>::foo::promoted[p]`
-                if let Some(p) = promoted {
-                    if self.def_id == def && !self.tcx.generics_of(def).has_self {
-                        // If there is a promoted, don't look at the args - since it will always contain
-                        // the generic parameters, instead, traverse the promoted MIR.
-                        let promoted = self.tcx.promoted_mir(def);
-                        self.visit_body(&promoted[p]);
-                    }
-                }
-
-                Visitor::visit_ty(self, ty, TyContext::Location(location));
-            }
-            mir::Const::Val(_, ty) => Visitor::visit_ty(self, ty, TyContext::Location(location)),
-        }
-    }
-
-    fn visit_ty(&mut self, ty: Ty<'tcx>, _: TyContext) {
-        ty.visit_with(self);
-    }
-}
-
-impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for MarkUsedGenericParams<'a, 'tcx> {
-    #[instrument(level = "debug", skip(self))]
-    fn visit_const(&mut self, c: ty::Const<'tcx>) {
-        if !c.has_non_region_param() {
-            return;
-        }
-
-        match c.kind() {
-            ty::ConstKind::Param(param) => {
-                debug!(?param);
-                self.unused_parameters.mark_used(param.index);
-            }
-            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args })
-                if matches!(self.tcx.def_kind(def), DefKind::AnonConst) =>
-            {
-                self.visit_child_body(def, args);
-            }
-            _ => c.super_visit_with(self),
-        }
-    }
-
-    #[instrument(level = "debug", skip(self))]
-    fn visit_ty(&mut self, ty: Ty<'tcx>) {
-        if !ty.has_non_region_param() {
-            return;
-        }
-
-        match *ty.kind() {
-            ty::Closure(def_id, args) | ty::Coroutine(def_id, args, ..) => {
-                debug!(?def_id);
-                // Avoid cycle errors with coroutines.
-                if def_id == self.def_id {
-                    return;
-                }
-
-                // Consider any generic parameters used by any closures/coroutines as used in the
-                // parent.
-                self.visit_child_body(def_id, args);
-            }
-            ty::Param(param) => {
-                debug!(?param);
-                self.unused_parameters.mark_used(param.index);
-            }
-            _ => ty.super_visit_with(self),
-        }
-    }
-}