Auto merge of #10793 - c410-f3r:bbbbbbbbbbb, r=xFrednet

[`arithmetic_side_effects`] Fix #10792

Fix #10792

```
changelog: [`arithmetic_side_effects`]: Retrieve field values of structures that are in constant environments
```

clippy_utils/src/consts.rs

@@ -14,7 +14,7 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::ty::{self, EarlyBinder, FloatTy, ScalarInt, Ty, TyCtxt};
 use rustc_middle::ty::{List, SubstsRef};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::SyntaxContext;
 use std::cmp::Ordering::{self, Equal};
 use std::hash::{Hash, Hasher};
@@ -22,7 +22,8 @@ use std::iter;
 
 /// A `LitKind`-like enum to fold constant `Expr`s into.
 #[derive(Debug, Clone)]
-pub enum Constant {
+pub enum Constant<'tcx> {
+    Adt(rustc_middle::mir::ConstantKind<'tcx>),
     /// A `String` (e.g., "abc").
     Str(String),
     /// A binary string (e.g., `b"abc"`).
@@ -38,20 +39,20 @@ pub enum Constant {
     /// `true` or `false`.
     Bool(bool),
     /// An array of constants.
-    Vec(Vec<Constant>),
+    Vec(Vec<Constant<'tcx>>),
     /// Also an array, but with only one constant, repeated N times.
-    Repeat(Box<Constant>, u64),
+    Repeat(Box<Constant<'tcx>>, u64),
     /// A tuple of constants.
-    Tuple(Vec<Constant>),
+    Tuple(Vec<Constant<'tcx>>),
     /// A raw pointer.
     RawPtr(u128),
     /// A reference
-    Ref(Box<Constant>),
+    Ref(Box<Constant<'tcx>>),
     /// A literal with syntax error.
     Err,
 }
 
-impl PartialEq for Constant {
+impl<'tcx> PartialEq for Constant<'tcx> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
             (Self::Str(ls), Self::Str(rs)) => ls == rs,
@@ -80,13 +81,16 @@ impl PartialEq for Constant {
     }
 }
 
-impl Hash for Constant {
+impl<'tcx> Hash for Constant<'tcx> {
     fn hash<H>(&self, state: &mut H)
     where
         H: Hasher,
     {
         std::mem::discriminant(self).hash(state);
         match *self {
+            Self::Adt(ref elem) => {
+                elem.hash(state);
+            },
             Self::Str(ref s) => {
                 s.hash(state);
             },
@@ -126,7 +130,7 @@ impl Hash for Constant {
     }
 }
 
-impl Constant {
+impl<'tcx> Constant<'tcx> {
     pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
         match (left, right) {
             (Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)),
@@ -209,7 +213,7 @@ impl Constant {
 }
 
 /// Parses a `LitKind` to a `Constant`.
-pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
+pub fn lit_to_mir_constant<'tcx>(lit: &LitKind, ty: Option<Ty<'tcx>>) -> Constant<'tcx> {
     match *lit {
         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
         LitKind::Byte(b) => Constant::Int(u128::from(b)),
@@ -248,7 +252,7 @@ pub fn constant<'tcx>(
     lcx: &LateContext<'tcx>,
     typeck_results: &ty::TypeckResults<'tcx>,
     e: &Expr<'_>,
-) -> Option<Constant> {
+) -> Option<Constant<'tcx>> {
     ConstEvalLateContext::new(lcx, typeck_results).expr(e)
 }
 
@@ -257,7 +261,7 @@ pub fn constant_with_source<'tcx>(
     lcx: &LateContext<'tcx>,
     typeck_results: &ty::TypeckResults<'tcx>,
     e: &Expr<'_>,
-) -> Option<(Constant, ConstantSource)> {
+) -> Option<(Constant<'tcx>, ConstantSource)> {
     let mut ctxt = ConstEvalLateContext::new(lcx, typeck_results);
     let res = ctxt.expr(e);
     res.map(|x| (x, ctxt.source))
@@ -268,7 +272,7 @@ pub fn constant_simple<'tcx>(
     lcx: &LateContext<'tcx>,
     typeck_results: &ty::TypeckResults<'tcx>,
     e: &Expr<'_>,
-) -> Option<Constant> {
+) -> Option<Constant<'tcx>> {
     constant_with_source(lcx, typeck_results, e).and_then(|(c, s)| s.is_local().then_some(c))
 }
 
@@ -338,7 +342,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
     }
 
     /// Simple constant folding: Insert an expression, get a constant or none.
-    pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
+    pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant<'tcx>> {
         match e.kind {
             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
             ExprKind::Block(block, _) => self.block(block),
@@ -392,13 +396,25 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
             },
             ExprKind::Index(arr, index) => self.index(arr, index),
             ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
-            // TODO: add other expressions.
+            ExprKind::Field(local_expr, ref field) => {
+                let result = self.expr(local_expr);
+                if let Some(Constant::Adt(constant)) = &self.expr(local_expr)
+                    && let ty::Adt(adt_def, _) = constant.ty().kind()
+                    && adt_def.is_struct()
+                    && let Some(desired_field) = field_of_struct(*adt_def, self.lcx, *constant, field)
+                {
+                    miri_to_const(self.lcx, desired_field)
+                }
+                else {
+                    result
+                }
+            },
             _ => None,
         }
     }
 
     #[expect(clippy::cast_possible_wrap)]
-    fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
+    fn constant_not(&self, o: &Constant<'tcx>, ty: Ty<'_>) -> Option<Constant<'tcx>> {
         use self::Constant::{Bool, Int};
         match *o {
             Bool(b) => Some(Bool(!b)),
@@ -414,7 +430,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         }
     }
 
-    fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
+    fn constant_negate(&self, o: &Constant<'tcx>, ty: Ty<'_>) -> Option<Constant<'tcx>> {
         use self::Constant::{Int, F32, F64};
         match *o {
             Int(value) => {
@@ -433,28 +449,25 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 
     /// Create `Some(Vec![..])` of all constants, unless there is any
     /// non-constant part.
-    fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
+    fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant<'tcx>>> {
         vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
     }
 
     /// Lookup a possibly constant expression from an `ExprKind::Path`.
-    fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
+    fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant<'tcx>> {
         let res = self.typeck_results.qpath_res(qpath, id);
         match res {
             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
                 // Check if this constant is based on `cfg!(..)`,
                 // which is NOT constant for our purposes.
-                if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id) &&
-                let Node::Item(&Item {
-                    kind: ItemKind::Const(_, body_id),
-                    ..
-                }) = node &&
-                let Node::Expr(&Expr {
-                    kind: ExprKind::Lit(_),
-                    span,
-                    ..
-                }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
-                is_direct_expn_of(span, "cfg").is_some() {
+                if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id)
+                    && let Node::Item(Item { kind: ItemKind::Const(_, body_id), .. }) = node
+                    && let Node::Expr(Expr { kind: ExprKind::Lit(_), span, .. }) = self.lcx
+                        .tcx
+                        .hir()
+                        .get(body_id.hir_id)
+                    && is_direct_expn_of(*span, "cfg").is_some()
+                {
                     return None;
                 }
 
@@ -464,23 +477,21 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                 } else {
                     EarlyBinder::bind(substs).subst(self.lcx.tcx, self.substs)
                 };
-
                 let result = self
                     .lcx
                     .tcx
                     .const_eval_resolve(self.param_env, mir::UnevaluatedConst::new(def_id, substs), None)
                     .ok()
                     .map(|val| rustc_middle::mir::ConstantKind::from_value(val, ty))?;
-                let result = miri_to_const(self.lcx.tcx, result)?;
+                let result = miri_to_const(self.lcx, result)?;
                 self.source = ConstantSource::Constant;
                 Some(result)
             },
-            // FIXME: cover all usable cases.
             _ => None,
         }
     }
 
-    fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
+    fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant<'tcx>> {
         let lhs = self.expr(lhs);
         let index = self.expr(index);
 
@@ -506,7 +517,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
     }
 
     /// A block can only yield a constant if it only has one constant expression.
-    fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
+    fn block(&mut self, block: &Block<'_>) -> Option<Constant<'tcx>> {
         if block.stmts.is_empty()
             && let Some(expr) = block.expr
         {
@@ -539,7 +550,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         }
     }
 
-    fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
+    fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant<'tcx>> {
         if let Some(Constant::Bool(b)) = self.expr(cond) {
             if b {
                 self.expr(then)
@@ -551,7 +562,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         }
     }
 
-    fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
+    fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant<'tcx>> {
         let l = self.expr(left)?;
         let r = self.expr(right);
         match (l, r) {
@@ -644,23 +655,21 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
     }
 }
 
-pub fn miri_to_const<'tcx>(tcx: TyCtxt<'tcx>, result: mir::ConstantKind<'tcx>) -> Option<Constant> {
+pub fn miri_to_const<'tcx>(lcx: &LateContext<'tcx>, result: mir::ConstantKind<'tcx>) -> Option<Constant<'tcx>> {
     use rustc_middle::mir::interpret::ConstValue;
     match result {
-        mir::ConstantKind::Val(ConstValue::Scalar(Scalar::Int(int)), _) => {
-            match result.ty().kind() {
-                ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
-                ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
-                ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
-                    int.try_into().expect("invalid f32 bit representation"),
-                ))),
-                ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
-                    int.try_into().expect("invalid f64 bit representation"),
-                ))),
-                ty::RawPtr(_) => Some(Constant::RawPtr(int.assert_bits(int.size()))),
-                // FIXME: implement other conversions.
-                _ => None,
-            }
+        mir::ConstantKind::Val(ConstValue::Scalar(Scalar::Int(int)), _) => match result.ty().kind() {
+            ty::Adt(adt_def, _) if adt_def.is_struct() => Some(Constant::Adt(result)),
+            ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
+            ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
+            ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
+                int.try_into().expect("invalid f32 bit representation"),
+            ))),
+            ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
+                int.try_into().expect("invalid f64 bit representation"),
+            ))),
+            ty::RawPtr(_) => Some(Constant::RawPtr(int.assert_bits(int.size()))),
+            _ => None,
         },
         mir::ConstantKind::Val(ConstValue::Slice { data, start, end }, _) => match result.ty().kind() {
             ty::Ref(_, tam, _) => match tam.kind() {
@@ -676,35 +685,53 @@ pub fn miri_to_const<'tcx>(tcx: TyCtxt<'tcx>, result: mir::ConstantKind<'tcx>) -
             _ => None,
         },
         mir::ConstantKind::Val(ConstValue::ByRef { alloc, offset: _ }, _) => match result.ty().kind() {
+            ty::Adt(adt_def, _) if adt_def.is_struct() => Some(Constant::Adt(result)),
             ty::Array(sub_type, len) => match sub_type.kind() {
-                ty::Float(FloatTy::F32) => match len.kind().try_to_target_usize(tcx) {
+                ty::Float(FloatTy::F32) => match len.kind().try_to_target_usize(lcx.tcx) {
                     Some(len) => alloc
                         .inner()
                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * usize::try_from(len).unwrap()))
                         .to_owned()
                         .array_chunks::<4>()
                         .map(|&chunk| Some(Constant::F32(f32::from_le_bytes(chunk))))
-                        .collect::<Option<Vec<Constant>>>()
+                        .collect::<Option<Vec<Constant<'tcx>>>>()
                         .map(Constant::Vec),
                     _ => None,
                 },
-                ty::Float(FloatTy::F64) => match len.kind().try_to_target_usize(tcx) {
+                ty::Float(FloatTy::F64) => match len.kind().try_to_target_usize(lcx.tcx) {
                     Some(len) => alloc
                         .inner()
                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * usize::try_from(len).unwrap()))
                         .to_owned()
                         .array_chunks::<8>()
                         .map(|&chunk| Some(Constant::F64(f64::from_le_bytes(chunk))))
-                        .collect::<Option<Vec<Constant>>>()
+                        .collect::<Option<Vec<Constant<'tcx>>>>()
                         .map(Constant::Vec),
                     _ => None,
                 },
-                // FIXME: implement other array type conversions.
                 _ => None,
             },
             _ => None,
         },
-        // FIXME: implement other conversions.
         _ => None,
     }
 }
+
+fn field_of_struct<'tcx>(
+    adt_def: ty::AdtDef<'tcx>,
+    lcx: &LateContext<'tcx>,
+    result: mir::ConstantKind<'tcx>,
+    field: &Ident,
+) -> Option<mir::ConstantKind<'tcx>> {
+    let dc = lcx.tcx.destructure_mir_constant(lcx.param_env, result);
+    if let Some(dc_variant) = dc.variant
+        && let Some(variant) = adt_def.variants().get(dc_variant)
+        && let Some(field_idx) = variant.fields.iter().position(|el| el.name == field.name)
+        && let Some(dc_field) = dc.fields.get(field_idx)
+    {
+        Some(*dc_field)
+    }
+    else {
+        None
+    }
+}

clippy_utils/src/lib.rs

@@ -1499,7 +1499,7 @@ pub fn is_range_full(cx: &LateContext<'_>, expr: &Expr<'_>, container_path: Opti
                 && let Some(min_val) = bnd_ty.numeric_min_val(cx.tcx)
                 && let const_val = cx.tcx.valtree_to_const_val((bnd_ty, min_val.to_valtree()))
                 && let min_const_kind = ConstantKind::from_value(const_val, bnd_ty)
-                && let Some(min_const) = miri_to_const(cx.tcx, min_const_kind)
+                && let Some(min_const) = miri_to_const(cx, min_const_kind)
                 && let Some(start_const) = constant(cx, cx.typeck_results(), start)
             {
                 start_const == min_const
@@ -1515,7 +1515,7 @@ pub fn is_range_full(cx: &LateContext<'_>, expr: &Expr<'_>, container_path: Opti
                         && let Some(max_val) = bnd_ty.numeric_max_val(cx.tcx)
                         && let const_val = cx.tcx.valtree_to_const_val((bnd_ty, max_val.to_valtree()))
                         && let max_const_kind = ConstantKind::from_value(const_val, bnd_ty)
-                        && let Some(max_const) = miri_to_const(cx.tcx, max_const_kind)
+                        && let Some(max_const) = miri_to_const(cx, max_const_kind)
                         && let Some(end_const) = constant(cx, cx.typeck_results(), end)
                     {
                         end_const == max_const