Change code to use map insead of for-loop

Author: bryangarza

compiler/rustc_mir_transform/src/ctfe_limit.rs

@@ -1,6 +1,8 @@
 use crate::MirPass;
 
-use rustc_middle::mir::{BasicBlockData, Body, Statement, StatementKind, TerminatorKind};
+use rustc_middle::mir::{
+    BasicBlock, BasicBlockData, Body, Statement, StatementKind, TerminatorKind,
+};
 use rustc_middle::ty::TyCtxt;
 
 pub struct CtfeLimit;
@@ -9,28 +11,28 @@ impl<'tcx> MirPass<'tcx> for CtfeLimit {
     #[instrument(skip(self, _tcx, body))]
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let doms = body.basic_blocks.dominators();
-        let mut indices = Vec::new();
-        for (node, node_data) in body.basic_blocks.iter_enumerated() {
-            if let TerminatorKind::Call { .. } = node_data.terminator().kind {
-                indices.push(node);
-                continue;
-            }
-            // Back edges in a CFG indicate loops
-            for (potential_dom, _) in body.basic_blocks.iter_enumerated() {
-                if doms.is_reachable(potential_dom)
-                    && doms.is_reachable(node)
-                    && doms.is_dominated_by(node, potential_dom)
-                    && node_data
-                        .terminator()
-                        .successors()
-                        .into_iter()
-                        .any(|succ| succ == potential_dom)
-                {
-                    indices.push(node);
-                    continue;
-                }
-            }
-        }
+        let indices: Vec<BasicBlock> =
+            body.basic_blocks
+                .iter_enumerated()
+                .filter_map(|(node, node_data)| {
+                    if matches!(node_data.terminator().kind, TerminatorKind::Call { .. }) ||
+                    // Back edges in a CFG indicate loops
+                    body.basic_blocks.iter_enumerated().any(|(potential_dom, _)| {
+                        doms.is_reachable(potential_dom)
+                            && doms.is_reachable(node)
+                            && doms.is_dominated_by(node, potential_dom)
+                            && node_data
+                                .terminator()
+                                .successors()
+                                .into_iter()
+                                .any(|succ| succ == potential_dom)
+                    }) {
+                        Some(node)
+                    } else {
+                        None
+                    }
+                })
+                .collect();
         for index in indices {
             insert_counter(
                 body.basic_blocks_mut()