refinement typing go brrrrrr

compiler/rustc_middle/src/mir/terminator.rs

@@ -417,6 +417,13 @@ impl<'tcx> TerminatorKind<'tcx> {
         }
     }
 
+    pub fn switch_targets_mut(&mut self) -> Option<&mut SwitchTargets> {
+        match self {
+            TerminatorKind::SwitchInt { targets, .. } => Some(targets),
+            _ => None,
+        }
+    }
+
     pub fn as_goto(&self) -> Option<BasicBlock> {
         match self {
             TerminatorKind::Goto { target } => Some(*target),

compiler/rustc_mir_dataflow/src/framework/mod.rs

@@ -530,6 +530,7 @@ impl EffectIndex {
     }
 }
 
+#[derive(Debug)]
 pub struct SwitchIntTarget {
     pub value: Option<u128>,
     pub target: BasicBlock,

compiler/rustc_mir_dataflow/src/lib.rs

@@ -31,7 +31,7 @@ pub use self::drop_flag_effects::{
 pub use self::framework::{
     fmt, graphviz, lattice, visit_results, Analysis, AnalysisDomain, Backward, Direction, Engine,
     Forward, GenKill, GenKillAnalysis, JoinSemiLattice, Results, ResultsCursor, ResultsRefCursor,
-    ResultsVisitable, ResultsVisitor,
+    ResultsVisitable, ResultsVisitor, SwitchIntEdgeEffects,
 };
 
 use self::move_paths::MoveData;

compiler/rustc_mir_transform/src/lib.rs

@@ -12,6 +12,7 @@
 #![feature(never_type)]
 #![feature(trusted_step)]
 #![feature(try_blocks)]
+#![feature(if_let_guard)]
 #![recursion_limit = "256"]
 #![cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
 
@@ -62,6 +63,7 @@ mod match_branches;
 mod multiple_return_terminators;
 mod normalize_array_len;
 mod nrvo;
+mod refinements;
 mod remove_noop_landing_pads;
 mod remove_storage_markers;
 mod remove_unneeded_drops;
@@ -507,6 +509,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 
     // The main optimizations that we do on MIR.
     let optimizations: &[&dyn MirPass<'tcx>] = &[
+        &refinements::Refinements,
         &remove_storage_markers::RemoveStorageMarkers,
         &remove_zsts::RemoveZsts,
         &const_goto::ConstGoto,