Rollup merge of rust-lang#105234 - JakobDegen:unneeded-field, r=oli-obk

Remove unneeded field from `SwitchTargets`

This had a fixme already. The only change in behavior is that the mir dumps now no longer contains labels for the types of the integers on the edges of a switchint:

Before:
![image](https://user-images.githubusercontent.com/51179609/205467622-34401a68-dca6-43eb-915e-b9fda1988860.png)

After:
![image](https://user-images.githubusercontent.com/51179609/205467634-b5b2a259-9cb4-4843-845c-592c500f0f9c.png)

I don't think that's a problem though. The information is still available to a user that really cares by checking the type of `_2`, so it honestly feels like a bit of an improvement to me.

r? mir

compiler/rustc_borrowck/src/invalidation.rs

@@ -106,7 +106,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
         self.check_activations(location);
 
         match &terminator.kind {
-            TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => {
+            TerminatorKind::SwitchInt { ref discr, targets: _ } => {
                 self.consume_operand(location, discr);
             }
             TerminatorKind::Drop { place: drop_place, target: _, unwind: _ } => {

compiler/rustc_borrowck/src/lib.rs

@@ -644,7 +644,7 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
         self.check_activations(loc, span, flow_state);
 
         match term.kind {
-            TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => {
+            TerminatorKind::SwitchInt { ref discr, targets: _ } => {
                 self.consume_operand(loc, (discr, span), flow_state);
             }
             TerminatorKind::Drop { place, target: _, unwind: _ } => {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1360,25 +1360,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     );
                 }
             }
-            TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
+            TerminatorKind::SwitchInt { ref discr, .. } => {
                 self.check_operand(discr, term_location);
 
-                let discr_ty = discr.ty(body, tcx);
-                if let Err(terr) = self.sub_types(
-                    discr_ty,
-                    switch_ty,
-                    term_location.to_locations(),
-                    ConstraintCategory::Assignment,
-                ) {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "bad SwitchInt ({:?} on {:?}): {:?}",
-                        switch_ty,
-                        discr_ty,
-                        terr
-                    );
-                }
+                let switch_ty = discr.ty(body, tcx);
                 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
                 }

compiler/rustc_codegen_cranelift/src/base.rs

@@ -372,8 +372,10 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                 }
             }
 
-            TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
-                let discr = codegen_operand(fx, discr).load_scalar(fx);
+            TerminatorKind::SwitchInt { discr, targets } => {
+                let discr = codegen_operand(fx, discr);
+                let switch_ty = discr.layout().ty;
+                let discr = discr.load_scalar(fx);
 
                 let use_bool_opt = switch_ty.kind() == fx.tcx.types.bool.kind()
                     || (targets.iter().count() == 1 && targets.iter().next().unwrap().0 == 0);

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -307,12 +307,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         helper: TerminatorCodegenHelper<'tcx>,
         bx: &mut Bx,
         discr: &mir::Operand<'tcx>,
-        switch_ty: Ty<'tcx>,
         targets: &SwitchTargets,
     ) {
         let discr = self.codegen_operand(bx, &discr);
-        // `switch_ty` is redundant, sanity-check that.
-        assert_eq!(discr.layout.ty, switch_ty);
+        let switch_ty = discr.layout.ty;
         let mut target_iter = targets.iter();
         if target_iter.len() == 1 {
             // If there are two targets (one conditional, one fallback), emit `br` instead of
@@ -1293,8 +1291,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 helper.funclet_br(self, bx, target, mergeable_succ())
             }
 
-            mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref targets } => {
-                self.codegen_switchint_terminator(helper, bx, discr, switch_ty, targets);
+            mir::TerminatorKind::SwitchInt { ref discr, ref targets } => {
+                self.codegen_switchint_terminator(helper, bx, discr, targets);
                 MergingSucc::False
             }
 

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -29,10 +29,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
             Goto { target } => self.go_to_block(target),
 
-            SwitchInt { ref discr, ref targets, switch_ty } => {
+            SwitchInt { ref discr, ref targets } => {
                 let discr = self.read_immediate(&self.eval_operand(discr, None)?)?;
                 trace!("SwitchInt({:?})", *discr);
-                assert_eq!(discr.layout.ty, switch_ty);
 
                 // Branch to the `otherwise` case by default, if no match is found.
                 let mut target_block = targets.otherwise();

compiler/rustc_const_eval/src/transform/validate.rs

@@ -682,17 +682,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             TerminatorKind::Goto { target } => {
                 self.check_edge(location, *target, EdgeKind::Normal);
             }
-            TerminatorKind::SwitchInt { targets, switch_ty, discr } => {
-                let ty = discr.ty(&self.body.local_decls, self.tcx);
-                if ty != *switch_ty {
-                    self.fail(
-                        location,
-                        format!(
-                            "encountered `SwitchInt` terminator with type mismatch: {:?} != {:?}",
-                            ty, switch_ty,
-                        ),
-                    );
-                }
+            TerminatorKind::SwitchInt { targets, discr } => {
+                let switch_ty = discr.ty(&self.body.local_decls, self.tcx);
 
                 let target_width = self.tcx.sess.target.pointer_width;
 

compiler/rustc_middle/src/mir/syntax.rs

@@ -518,12 +518,6 @@ pub enum TerminatorKind<'tcx> {
     SwitchInt {
         /// The discriminant value being tested.
         discr: Operand<'tcx>,
-
-        /// The type of value being tested.
-        /// This is always the same as the type of `discr`.
-        /// FIXME: remove this redundant information. Currently, it is relied on by pretty-printing.
-        switch_ty: Ty<'tcx>,
-
         targets: SwitchTargets,
     },
 

compiler/rustc_middle/src/mir/terminator.rs

@@ -1,6 +1,3 @@
-use crate::mir;
-use crate::mir::interpret::Scalar;
-use crate::ty::{self, Ty, TyCtxt};
 use smallvec::{smallvec, SmallVec};
 
 use super::{BasicBlock, InlineAsmOperand, Operand, SourceInfo, TerminatorKind};
@@ -131,17 +128,8 @@ impl<'tcx> Terminator<'tcx> {
 }
 
 impl<'tcx> TerminatorKind<'tcx> {
-    pub fn if_(
-        tcx: TyCtxt<'tcx>,
-        cond: Operand<'tcx>,
-        t: BasicBlock,
-        f: BasicBlock,
-    ) -> TerminatorKind<'tcx> {
-        TerminatorKind::SwitchInt {
-            discr: cond,
-            switch_ty: tcx.types.bool,
-            targets: SwitchTargets::static_if(0, f, t),
-        }
+    pub fn if_(cond: Operand<'tcx>, t: BasicBlock, f: BasicBlock) -> TerminatorKind<'tcx> {
+        TerminatorKind::SwitchInt { discr: cond, targets: SwitchTargets::static_if(0, f, t) }
     }
 
     pub fn successors(&self) -> Successors<'_> {
@@ -264,11 +252,9 @@ impl<'tcx> TerminatorKind<'tcx> {
         }
     }
 
-    pub fn as_switch(&self) -> Option<(&Operand<'tcx>, Ty<'tcx>, &SwitchTargets)> {
+    pub fn as_switch(&self) -> Option<(&Operand<'tcx>, &SwitchTargets)> {
         match self {
-            TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
-                Some((discr, *switch_ty, targets))
-            }
+            TerminatorKind::SwitchInt { discr, targets } => Some((discr, targets)),
             _ => None,
         }
     }
@@ -403,21 +389,12 @@ impl<'tcx> TerminatorKind<'tcx> {
         match *self {
             Return | Resume | Abort | Unreachable | GeneratorDrop => vec![],
             Goto { .. } => vec!["".into()],
-            SwitchInt { ref targets, switch_ty, .. } => ty::tls::with(|tcx| {
-                let param_env = ty::ParamEnv::empty();
-                let switch_ty = tcx.lift(switch_ty).unwrap();
-                let size = tcx.layout_of(param_env.and(switch_ty)).unwrap().size;
-                targets
-                    .values
-                    .iter()
-                    .map(|&u| {
-                        mir::ConstantKind::from_scalar(tcx, Scalar::from_uint(u, size), switch_ty)
-                            .to_string()
-                            .into()
-                    })
-                    .chain(iter::once("otherwise".into()))
-                    .collect()
-            }),
+            SwitchInt { ref targets, .. } => targets
+                .values
+                .iter()
+                .map(|&u| Cow::Owned(u.to_string()))
+                .chain(iter::once("otherwise".into()))
+                .collect(),
             Call { target: Some(_), cleanup: Some(_), .. } => {
                 vec!["return".into(), "unwind".into()]
             }

compiler/rustc_middle/src/mir/visit.rs

@@ -477,11 +477,9 @@ macro_rules! make_mir_visitor {
 
                     TerminatorKind::SwitchInt {
                         discr,
-                        switch_ty,
                         targets: _
                     } => {
                         self.visit_operand(discr, location);
-                        self.visit_ty($(& $mutability)? *switch_ty, TyContext::Location(location));
                     }
 
                     TerminatorKind::Drop {

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -183,7 +183,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     LogicalOp::And => (else_block, shortcircuit_block),
                     LogicalOp::Or => (shortcircuit_block, else_block),
                 };
-                let term = TerminatorKind::if_(this.tcx, lhs, blocks.0, blocks.1);
+                let term = TerminatorKind::if_(lhs, blocks.0, blocks.1);
                 this.cfg.terminate(block, source_info, term);
 
                 this.cfg.push_assign_constant(

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -95,7 +95,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                 let then_block = this.cfg.start_new_block();
                 let else_block = this.cfg.start_new_block();
-                let term = TerminatorKind::if_(this.tcx, operand, then_block, else_block);
+                let term = TerminatorKind::if_(operand, then_block, else_block);
 
                 let source_info = this.source_info(expr_span);
                 this.cfg.terminate(block, source_info, term);

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -203,7 +203,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     self.source_info(match_start_span),
                     TerminatorKind::SwitchInt {
                         discr: Operand::Move(discr),
-                        switch_ty: discr_ty,
                         targets: switch_targets,
                     },
                 );
@@ -221,7 +220,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         0 => (second_bb, first_bb),
                         v => span_bug!(test.span, "expected boolean value but got {:?}", v),
                     };
-                    TerminatorKind::if_(self.tcx, Operand::Copy(place), true_bb, false_bb)
+                    TerminatorKind::if_(Operand::Copy(place), true_bb, false_bb)
                 } else {
                     // The switch may be inexhaustive so we have a catch all block
                     debug_assert_eq!(options.len() + 1, target_blocks.len());
@@ -232,7 +231,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     );
                     TerminatorKind::SwitchInt {
                         discr: Operand::Copy(place),
-                        switch_ty,
                         targets: switch_targets,
                     }
                 };
@@ -378,7 +376,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         self.cfg.terminate(
             block,
             source_info,
-            TerminatorKind::if_(self.tcx, Operand::Move(result), success_block, fail_block),
+            TerminatorKind::if_(Operand::Move(result), success_block, fail_block),
         );
     }
 
@@ -482,7 +480,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         self.cfg.terminate(
             eq_block,
             source_info,
-            TerminatorKind::if_(self.tcx, Operand::Move(eq_result), success_block, fail_block),
+            TerminatorKind::if_(Operand::Move(eq_result), success_block, fail_block),
         );
     }
 

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -596,7 +596,6 @@ where
                 source_info: self.source_info,
                 kind: TerminatorKind::SwitchInt {
                     discr: Operand::Move(discr),
-                    switch_ty: discr_ty,
                     targets: SwitchTargets::new(
                         values.iter().copied().zip(blocks.iter().copied()),
                         *blocks.last().unwrap(),
@@ -716,7 +715,7 @@ where
             is_cleanup: unwind.is_cleanup(),
             terminator: Some(Terminator {
                 source_info: self.source_info,
-                kind: TerminatorKind::if_(tcx, move_(can_go), succ, drop_block),
+                kind: TerminatorKind::if_(move_(can_go), succ, drop_block),
             }),
         };
         let loop_block = self.elaborator.patch().new_block(loop_block);
@@ -781,7 +780,6 @@ where
                 source_info: self.source_info,
                 kind: TerminatorKind::SwitchInt {
                     discr: move_(elem_size),
-                    switch_ty: tcx.types.usize,
                     targets: SwitchTargets::static_if(
                         0,
                         self.drop_loop_pair(ety, false, len),
@@ -1021,7 +1019,7 @@ where
             DropStyle::Static => on_set,
             DropStyle::Conditional | DropStyle::Open => {
                 let flag = self.elaborator.get_drop_flag(self.path).unwrap();
-                let term = TerminatorKind::if_(self.tcx(), flag, on_set, on_unset);
+                let term = TerminatorKind::if_(flag, on_set, on_unset);
                 self.new_block(unwind, term)
             }
         }

compiler/rustc_mir_dataflow/src/framework/direction.rs

@@ -261,7 +261,7 @@ impl Direction for Backward {
                     propagate(pred, &tmp);
                 }
 
-                mir::TerminatorKind::SwitchInt { targets: _, ref discr, switch_ty: _ } => {
+                mir::TerminatorKind::SwitchInt { targets: _, ref discr } => {
                     let mut applier = BackwardSwitchIntEdgeEffectsApplier {
                         body,
                         pred,
@@ -577,7 +577,7 @@ impl Direction for Forward {
                 }
             }
 
-            SwitchInt { ref targets, ref discr, switch_ty: _ } => {
+            SwitchInt { ref targets, ref discr } => {
                 let mut applier = ForwardSwitchIntEdgeEffectsApplier {
                     exit_state,
                     targets,

compiler/rustc_mir_transform/src/const_goto.rs

@@ -82,8 +82,9 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
                 }
 
                 let target_bb_terminator = target_bb.terminator();
-                let (discr, switch_ty, targets) = target_bb_terminator.kind.as_switch()?;
+                let (discr, targets) = target_bb_terminator.kind.as_switch()?;
                 if discr.place() == Some(*place) {
+                    let switch_ty = place.ty(self.body.local_decls(), self.tcx).ty;
                     // We now know that the Switch matches on the const place, and it is statementless
                     // Now find which value in the Switch matches the const value.
                     let const_value =

compiler/rustc_mir_transform/src/coverage/tests.rs

@@ -37,7 +37,7 @@ use rustc_data_structures::graph::WithSuccessors;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty;
 use rustc_span::{self, BytePos, Pos, Span, DUMMY_SP};
 
 // All `TEMP_BLOCK` targets should be replaced before calling `to_body() -> mir::Body`.
@@ -47,7 +47,6 @@ struct MockBlocks<'tcx> {
     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
     dummy_place: Place<'tcx>,
     next_local: usize,
-    bool_ty: Ty<'tcx>,
 }
 
 impl<'tcx> MockBlocks<'tcx> {
@@ -56,7 +55,6 @@ impl<'tcx> MockBlocks<'tcx> {
             blocks: IndexVec::new(),
             dummy_place: Place { local: RETURN_PLACE, projection: ty::List::empty() },
             next_local: 0,
-            bool_ty: TyCtxt::BOOL_TY_FOR_UNIT_TESTING,
         }
     }
 
@@ -157,7 +155,6 @@ impl<'tcx> MockBlocks<'tcx> {
     fn switchint(&mut self, some_from_block: Option<BasicBlock>) -> BasicBlock {
         let switchint_kind = TerminatorKind::SwitchInt {
             discr: Operand::Move(Place::from(self.new_temp())),
-            switch_ty: self.bool_ty, // just a dummy value
             targets: SwitchTargets::static_if(0, TEMP_BLOCK, TEMP_BLOCK),
         };
         self.add_block_from(some_from_block, switchint_kind)