Inline and remove BasicBlockData::retain_statements.

It has a single call site, and the code is clearer this way.

Author: nnethercote

Diff for: compiler/rustc_middle/src/mir/mod.rs

@@ -1365,17 +1365,6 @@ impl<'tcx> BasicBlockData<'tcx> {
         self.terminator.as_mut().expect("invalid terminator state")
     }
 
-    pub fn retain_statements<F>(&mut self, mut f: F)
-    where
-        F: FnMut(&mut Statement<'_>) -> bool,
-    {
-        for s in &mut self.statements {
-            if !f(s) {
-                s.make_nop();
-            }
-        }
-    }
-
     pub fn visitable(&self, index: usize) -> &dyn MirVisitable<'tcx> {
         if index < self.statements.len() { &self.statements[index] } else { &self.terminator }
     }

Diff for: compiler/rustc_mir_transform/src/coroutine.rs

@@ -393,12 +393,13 @@ impl<'tcx> MutVisitor<'tcx> for TransformVisitor<'tcx> {
 
     fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
         // Remove StorageLive and StorageDead statements for remapped locals
-        data.retain_statements(|s| match s.kind {
-            StatementKind::StorageLive(l) | StatementKind::StorageDead(l) => {
-                !self.remap.contains(l)
+        for s in &mut data.statements {
+            if let StatementKind::StorageLive(l) | StatementKind::StorageDead(l) = s.kind
+                && self.remap.contains(l)
+            {
+                s.make_nop();
             }
-            _ => true,
-        });
+        }
 
         let ret_val = match data.terminator().kind {
             TerminatorKind::Return => {