Change Direction::{is_forward,is_backward} functions into constants

compiler/rustc_mir_dataflow/src/framework/cursor.rs

@@ -109,7 +109,7 @@ where
     /// For backward analyses, this is the state that will be propagated to its
     /// predecessors (ignoring edge-specific effects).
     pub fn seek_to_block_start(&mut self, block: BasicBlock) {
-        if A::Direction::is_forward() {
+        if A::Direction::IS_FORWARD {
             self.seek_to_block_entry(block)
         } else {
             self.seek_after(Location { block, statement_index: 0 }, Effect::Primary)
@@ -123,7 +123,7 @@ where
     /// For forward analyses, this is the state that will be propagated to its
     /// successors (ignoring edge-specific effects).
     pub fn seek_to_block_end(&mut self, block: BasicBlock) {
-        if A::Direction::is_backward() {
+        if A::Direction::IS_BACKWARD {
             self.seek_to_block_entry(block)
         } else {
             self.seek_after(self.body.terminator_loc(block), Effect::Primary)
@@ -157,7 +157,7 @@ where
             self.seek_to_block_entry(target.block);
         } else if let Some(curr_effect) = self.pos.curr_effect_index {
             let mut ord = curr_effect.statement_index.cmp(&target.statement_index);
-            if A::Direction::is_backward() {
+            if A::Direction::IS_BACKWARD {
                 ord = ord.reverse()
             }
 
@@ -173,7 +173,7 @@ where
         debug_assert_eq!(target.block, self.pos.block);
 
         let block_data = &self.body[target.block];
-        let next_effect = if A::Direction::is_forward() {
+        let next_effect = if A::Direction::IS_FORWARD {
             #[rustfmt::skip]
             self.pos.curr_effect_index.map_or_else(
                 || Effect::Before.at_index(0),

compiler/rustc_mir_dataflow/src/framework/direction.rs

@@ -9,11 +9,9 @@ use super::{
 };
 
 pub trait Direction {
-    fn is_forward() -> bool;
+    const IS_FORWARD: bool;
 
-    fn is_backward() -> bool {
-        !Self::is_forward()
-    }
+    const IS_BACKWARD: bool = !Self::IS_FORWARD;
 
     /// Applies all effects between the given `EffectIndex`s.
     ///
@@ -68,9 +66,7 @@ pub trait Direction {
 pub struct Backward;
 
 impl Direction for Backward {
-    fn is_forward() -> bool {
-        false
-    }
+    const IS_FORWARD: bool = false;
 
     fn apply_effects_in_block<'tcx, A>(
         analysis: &A,
@@ -338,9 +334,7 @@ where
 pub struct Forward;
 
 impl Direction for Forward {
-    fn is_forward() -> bool {
-        true
-    }
+    const IS_FORWARD: bool = true;
 
     fn apply_effects_in_block<'tcx, A>(
         analysis: &A,

compiler/rustc_mir_dataflow/src/framework/engine.rs

@@ -147,7 +147,7 @@ where
         let mut entry_sets = IndexVec::from_elem(bottom_value.clone(), body.basic_blocks());
         analysis.initialize_start_block(body, &mut entry_sets[mir::START_BLOCK]);
 
-        if A::Direction::is_backward() && entry_sets[mir::START_BLOCK] != bottom_value {
+        if A::Direction::IS_BACKWARD && entry_sets[mir::START_BLOCK] != bottom_value {
             bug!("`initialize_start_block` is not yet supported for backward dataflow analyses");
         }
 
@@ -200,7 +200,7 @@ where
         let mut dirty_queue: WorkQueue<BasicBlock> =
             WorkQueue::with_none(body.basic_blocks().len());
 
-        if A::Direction::is_forward() {
+        if A::Direction::IS_FORWARD {
             for (bb, _) in traversal::reverse_postorder(body) {
                 dirty_queue.insert(bb);
             }

compiler/rustc_mir_dataflow/src/framework/graphviz.rs

@@ -216,7 +216,7 @@ where
         // Write the full dataflow state immediately after the terminator if it differs from the
         // state at block entry.
         self.results.seek_to_block_end(block);
-        if self.results.get() != &block_start_state || A::Direction::is_backward() {
+        if self.results.get() != &block_start_state || A::Direction::IS_BACKWARD {
             let after_terminator_name = match terminator.kind {
                 mir::TerminatorKind::Call { target: Some(_), .. } => "(on unwind)",
                 _ => "(on end)",
@@ -390,7 +390,7 @@ where
         let mut afters = diffs.after.into_iter();
 
         let next_in_dataflow_order = |it: &mut std::vec::IntoIter<_>| {
-            if A::Direction::is_forward() { it.next().unwrap() } else { it.next_back().unwrap() }
+            if A::Direction::IS_FORWARD { it.next().unwrap() } else { it.next_back().unwrap() }
         };
 
         for (i, statement) in body[block].statements.iter().enumerate() {
@@ -527,7 +527,7 @@ where
         _block_data: &mir::BasicBlockData<'tcx>,
         _block: BasicBlock,
     ) {
-        if A::Direction::is_forward() {
+        if A::Direction::IS_FORWARD {
             self.prev_state.clone_from(state);
         }
     }
@@ -538,7 +538,7 @@ where
         _block_data: &mir::BasicBlockData<'tcx>,
         _block: BasicBlock,
     ) {
-        if A::Direction::is_backward() {
+        if A::Direction::IS_BACKWARD {
             self.prev_state.clone_from(state);
         }
     }

compiler/rustc_mir_dataflow/src/framework/tests.rs

@@ -140,7 +140,7 @@ impl<D: Direction> MockAnalysis<'_, D> {
             SeekTarget::After(loc) => Effect::Primary.at_index(loc.statement_index),
         };
 
-        let mut pos = if D::is_forward() {
+        let mut pos = if D::IS_FORWARD {
             Effect::Before.at_index(0)
         } else {
             Effect::Before.at_index(self.body[block].statements.len())
@@ -153,7 +153,7 @@ impl<D: Direction> MockAnalysis<'_, D> {
                 return ret;
             }
 
-            if D::is_forward() {
+            if D::IS_FORWARD {
                 pos = pos.next_in_forward_order();
             } else {
                 pos = pos.next_in_backward_order();