Rollup merge of #150411 - Kivooeo:somefunnystuff, r=BoxyUwU

refactor `destructure_const`

r? BoxyUwU

as you suggested yesterday (will add more context like links when it stops being a draft)

tried to split this into some meaningful commits hope it help ^^

Author: JonathanBrouwer

compiler/rustc_middle/src/mir/pretty.rs

@@ -1896,7 +1896,8 @@ fn pretty_print_const_value_tcx<'tcx>(
         // Aggregates, printed as array/tuple/struct/variant construction syntax.
         //
         // NB: the `has_non_region_param` check ensures that we can use
-        // the `destructure_const` query with an empty `ty::ParamEnv` without
+        // the `try_destructure_mir_constant_for_user_output ` query with
+        // an empty `TypingEnv::fully_monomorphized` without
         // introducing ICEs (e.g. via `layout_of`) from missing bounds.
         // E.g. `transmute([0usize; 2]): (u8, *mut T)` needs to know `T: Sized`
         // to be able to destructure the tuple into `(0u8, *mut T)`

compiler/rustc_middle/src/query/erase.rs

@@ -402,7 +402,7 @@ tcx_lifetime! {
     rustc_middle::ty::ClauseKind,
     rustc_middle::ty::ClosureTypeInfo,
     rustc_middle::ty::Const,
-    rustc_middle::ty::DestructuredConst,
+    rustc_middle::ty::DestructuredAdtConst,
     rustc_middle::ty::ExistentialTraitRef,
     rustc_middle::ty::FnSig,
     rustc_middle::ty::GenericArg,

compiler/rustc_middle/src/query/mod.rs

@@ -1408,12 +1408,6 @@ rustc_queries! {
         desc { "converting type-level constant value to MIR constant value"}
     }
 
-    /// Destructures array, ADT or tuple constants into the constants
-    /// of their fields.
-    query destructure_const(key: ty::Const<'tcx>) -> ty::DestructuredConst<'tcx> {
-        desc { "destructuring type level constant"}
-    }
-
     // FIXME get rid of this with valtrees
     query lit_to_const(
         key: LitToConstInput<'tcx>

compiler/rustc_middle/src/ty/consts/valtree.rs

@@ -1,6 +1,7 @@
 use std::fmt;
 use std::ops::Deref;
 
+use rustc_abi::{FIRST_VARIANT, VariantIdx};
 use rustc_data_structures::intern::Interned;
 use rustc_hir::def::Namespace;
 use rustc_macros::{
@@ -189,6 +190,26 @@ impl<'tcx> Value<'tcx> {
             ValTreeKind::Leaf(_) => None,
         }
     }
+
+    /// Destructures array, ADT or tuple constants into the constants
+    /// of their fields.
+    pub fn destructure_adt_const(&self) -> ty::DestructuredAdtConst<'tcx> {
+        let fields = self.to_branch();
+
+        let (variant, fields) = match self.ty.kind() {
+            ty::Adt(def, _) if def.variants().is_empty() => {
+                bug!("unreachable")
+            }
+            ty::Adt(def, _) if def.is_enum() => {
+                let (head, rest) = fields.split_first().unwrap();
+                (VariantIdx::from_u32(head.to_leaf().to_u32()), rest)
+            }
+            ty::Adt(_, _) => (FIRST_VARIANT, fields),
+            _ => bug!("destructure_adt_const called on non-ADT type: {:?}", self.ty),
+        };
+
+        ty::DestructuredAdtConst { variant, fields }
+    }
 }
 
 impl<'tcx> rustc_type_ir::inherent::ValueConst<TyCtxt<'tcx>> for Value<'tcx> {

compiler/rustc_middle/src/ty/mod.rs

@@ -2331,8 +2331,8 @@ impl<'tcx> fmt::Debug for SymbolName<'tcx> {
 
 /// The constituent parts of a type level constant of kind ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
-pub struct DestructuredConst<'tcx> {
-    pub variant: Option<VariantIdx>,
+pub struct DestructuredAdtConst<'tcx> {
+    pub variant: VariantIdx,
     pub fields: &'tcx [ty::Const<'tcx>],
 }
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1919,66 +1919,65 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 self.pretty_print_byte_str(bytes)?;
                 return Ok(());
             }
-            // Aggregates, printed as array/tuple/struct/variant construction syntax.
-            (ty::ValTreeKind::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
-                let contents = self.tcx().destructure_const(ty::Const::new_value(
-                    self.tcx(),
-                    cv.valtree,
-                    cv.ty,
-                ));
-                let fields = contents.fields.iter().copied();
+            (ty::ValTreeKind::Branch(fields), ty::Array(..) | ty::Tuple(..)) => {
+                let fields_iter = fields.iter().copied();
+
                 match *cv.ty.kind() {
                     ty::Array(..) => {
                         write!(self, "[")?;
-                        self.comma_sep(fields)?;
+                        self.comma_sep(fields_iter)?;
                         write!(self, "]")?;
                     }
                     ty::Tuple(..) => {
                         write!(self, "(")?;
-                        self.comma_sep(fields)?;
-                        if contents.fields.len() == 1 {
+                        self.comma_sep(fields_iter)?;
+                        if fields.len() == 1 {
                             write!(self, ",")?;
                         }
                         write!(self, ")")?;
                     }
-                    ty::Adt(def, _) if def.variants().is_empty() => {
-                        self.typed_value(
-                            |this| {
-                                write!(this, "unreachable()")?;
-                                Ok(())
-                            },
-                            |this| this.print_type(cv.ty),
-                            ": ",
-                        )?;
-                    }
-                    ty::Adt(def, args) => {
-                        let variant_idx =
-                            contents.variant.expect("destructed const of adt without variant idx");
-                        let variant_def = &def.variant(variant_idx);
-                        self.pretty_print_value_path(variant_def.def_id, args)?;
-                        match variant_def.ctor_kind() {
-                            Some(CtorKind::Const) => {}
-                            Some(CtorKind::Fn) => {
-                                write!(self, "(")?;
-                                self.comma_sep(fields)?;
-                                write!(self, ")")?;
-                            }
-                            None => {
-                                write!(self, " {{ ")?;
-                                let mut first = true;
-                                for (field_def, field) in iter::zip(&variant_def.fields, fields) {
-                                    if !first {
-                                        write!(self, ", ")?;
-                                    }
-                                    write!(self, "{}: ", field_def.name)?;
-                                    field.print(self)?;
-                                    first = false;
+                    _ => unreachable!(),
+                }
+                return Ok(());
+            }
+            (ty::ValTreeKind::Branch(_), ty::Adt(def, args)) => {
+                let contents = cv.destructure_adt_const();
+                let fields = contents.fields.iter().copied();
+
+                if def.variants().is_empty() {
+                    self.typed_value(
+                        |this| {
+                            write!(this, "unreachable()")?;
+                            Ok(())
+                        },
+                        |this| this.print_type(cv.ty),
+                        ": ",
+                    )?;
+                } else {
+                    let variant_idx = contents.variant;
+                    let variant_def = &def.variant(variant_idx);
+                    self.pretty_print_value_path(variant_def.def_id, args)?;
+                    match variant_def.ctor_kind() {
+                        Some(CtorKind::Const) => {}
+                        Some(CtorKind::Fn) => {
+                            write!(self, "(")?;
+                            self.comma_sep(fields)?;
+                            write!(self, ")")?;
+                        }
+                        None => {
+                            write!(self, " {{ ")?;
+                            let mut first = true;
+                            for (field_def, field) in iter::zip(&variant_def.fields, fields) {
+                                if !first {
+                                    write!(self, ", ")?;
                                 }
-                                write!(self, " }}")?;
+                                write!(self, "{}: ", field_def.name)?;
+                                field.print(self)?;
+                                first = false;
                             }
+                            write!(self, " }}")?;
                         }
                     }
-                    _ => unreachable!(),
                 }
                 return Ok(());
             }

compiler/rustc_symbol_mangling/src/v0.rs

@@ -755,9 +755,8 @@ impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
                 dereferenced_const.print(self)?;
             }
 
-            ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {
-                let contents = self.tcx.destructure_const(ct);
-                let fields = contents.fields.iter().copied();
+            ty::Array(..) | ty::Tuple(..) | ty::Slice(_) => {
+                let fields = cv.to_branch().iter().copied();
 
                 let print_field_list = |this: &mut Self| {
                     for field in fields.clone() {
@@ -776,43 +775,51 @@ impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
                         self.push("T");
                         print_field_list(self)?;
                     }
-                    ty::Adt(def, args) => {
-                        let variant_idx =
-                            contents.variant.expect("destructed const of adt without variant idx");
-                        let variant_def = &def.variant(variant_idx);
+                    _ => unreachable!(),
+                }
+            }
+            ty::Adt(def, args) => {
+                let contents = cv.destructure_adt_const();
+                let fields = contents.fields.iter().copied();
+
+                let print_field_list = |this: &mut Self| {
+                    for field in fields.clone() {
+                        field.print(this)?;
+                    }
+                    this.push("E");
+                    Ok(())
+                };
 
-                        self.push("V");
-                        self.print_def_path(variant_def.def_id, args)?;
+                let variant_idx = contents.variant;
+                let variant_def = &def.variant(variant_idx);
 
-                        match variant_def.ctor_kind() {
-                            Some(CtorKind::Const) => {
-                                self.push("U");
-                            }
-                            Some(CtorKind::Fn) => {
-                                self.push("T");
-                                print_field_list(self)?;
-                            }
-                            None => {
-                                self.push("S");
-                                for (field_def, field) in iter::zip(&variant_def.fields, fields) {
-                                    // HACK(eddyb) this mimics `print_path_with_simple`,
-                                    // instead of simply using `field_def.ident`,
-                                    // just to be able to handle disambiguators.
-                                    let disambiguated_field =
-                                        self.tcx.def_key(field_def.did).disambiguated_data;
-                                    let field_name = disambiguated_field.data.get_opt_name();
-                                    self.push_disambiguator(
-                                        disambiguated_field.disambiguator as u64,
-                                    );
-                                    self.push_ident(field_name.unwrap().as_str());
-
-                                    field.print(self)?;
-                                }
-                                self.push("E");
-                            }
+                self.push("V");
+                self.print_def_path(variant_def.def_id, args)?;
+
+                match variant_def.ctor_kind() {
+                    Some(CtorKind::Const) => {
+                        self.push("U");
+                    }
+                    Some(CtorKind::Fn) => {
+                        self.push("T");
+                        print_field_list(self)?;
+                    }
+                    None => {
+                        self.push("S");
+                        for (field_def, field) in iter::zip(&variant_def.fields, fields) {
+                            // HACK(eddyb) this mimics `print_path_with_simple`,
+                            // instead of simply using `field_def.ident`,
+                            // just to be able to handle disambiguators.
+                            let disambiguated_field =
+                                self.tcx.def_key(field_def.did).disambiguated_data;
+                            let field_name = disambiguated_field.data.get_opt_name();
+                            self.push_disambiguator(disambiguated_field.disambiguator as u64);
+                            self.push_ident(field_name.unwrap().as_str());
+
+                            field.print(self)?;
                         }
+                        self.push("E");
                     }
-                    _ => unreachable!(),
                 }
             }
             _ => {

compiler/rustc_ty_utils/src/consts.rs

@@ -1,6 +1,3 @@
-use std::iter;
-
-use rustc_abi::{FIRST_VARIANT, VariantIdx};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
@@ -10,63 +7,12 @@ use rustc_middle::thir::visit;
 use rustc_middle::thir::visit::Visitor;
 use rustc_middle::ty::abstract_const::CastKind;
 use rustc_middle::ty::{self, Expr, TyCtxt, TypeVisitableExt};
-use rustc_middle::{bug, mir, thir};
+use rustc_middle::{mir, thir};
 use rustc_span::Span;
-use tracing::{debug, instrument};
+use tracing::instrument;
 
 use crate::errors::{GenericConstantTooComplex, GenericConstantTooComplexSub};
 
-/// Destructures array, ADT or tuple constants into the constants
-/// of their fields.
-fn destructure_const<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    const_: ty::Const<'tcx>,
-) -> ty::DestructuredConst<'tcx> {
-    let ty::ConstKind::Value(cv) = const_.kind() else {
-        bug!("cannot destructure constant {:?}", const_)
-    };
-    let branches = cv.to_branch();
-
-    let (fields, variant) = match cv.ty.kind() {
-        ty::Array(inner_ty, _) | ty::Slice(inner_ty) => {
-            // construct the consts for the elements of the array/slice
-            let field_consts = branches
-                .iter()
-                .map(|b| ty::Const::new_value(tcx, b.to_value().valtree, *inner_ty))
-                .collect::<Vec<_>>();
-            debug!(?field_consts);
-
-            (field_consts, None)
-        }
-        ty::Adt(def, _) if def.variants().is_empty() => bug!("unreachable"),
-        ty::Adt(def, _) => {
-            let (variant_idx, field_consts) = if def.is_enum() {
-                let (head, rest) = branches.split_first().unwrap();
-                (VariantIdx::from_u32(head.to_leaf().to_u32()), rest)
-            } else {
-                (FIRST_VARIANT, branches)
-            };
-            debug!(?field_consts);
-
-            (field_consts.to_vec(), Some(variant_idx))
-        }
-        ty::Tuple(elem_tys) => {
-            let fields = iter::zip(*elem_tys, branches)
-                .map(|(elem_ty, elem_valtree)| {
-                    ty::Const::new_value(tcx, elem_valtree.to_value().valtree, elem_ty)
-                })
-                .collect::<Vec<_>>();
-
-            (fields, None)
-        }
-        _ => bug!("cannot destructure constant {:?}", const_),
-    };
-
-    let fields = tcx.arena.alloc_from_iter(fields);
-
-    ty::DestructuredConst { variant, fields }
-}
-
 /// We do not allow all binary operations in abstract consts, so filter disallowed ones.
 fn check_binop(op: mir::BinOp) -> bool {
     use mir::BinOp::*;
@@ -432,5 +378,5 @@ fn thir_abstract_const<'tcx>(
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { destructure_const, thir_abstract_const, ..*providers };
+    *providers = Providers { thir_abstract_const, ..*providers };
 }

tests/crashes/131052.rs

@@ -0,0 +1,13 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/131052>
+
+#![feature(adt_const_params)]
+
+struct ConstBytes<const T: &'static [*mut u8; 3]>;
+//~^ ERROR `&'static [*mut u8; 3]` can't be used as a const parameter type
+
+pub fn main() {
+    let _: ConstBytes<b"AAA"> = ConstBytes::<b"BBB">;
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+}