From 0ceb7e2fae841be5662b0bf71a33e9d9083ec11d Mon Sep 17 00:00:00 2001
From: zseri <zseri.devel@ytrizja.de>
Date: Sat, 27 Mar 2021 08:25:06 +0100
Subject: deeper optimizations

---
 src/makefile/mod.rs | 59 ++++++++++++++++++++++++++---------------------------
 1 file changed, 29 insertions(+), 30 deletions(-)

diff --git a/src/makefile/mod.rs b/src/makefile/mod.rs
index dae742f..735c8aa 100644
--- a/src/makefile/mod.rs
+++ b/src/makefile/mod.rs
@@ -565,13 +565,9 @@ impl<'a> Makefile<'a> {
         let targets = self.targets.borrow();
         let mut new_target = None;
         let exists_but_infer_anyway = if follow_gnu {
-            match targets.get(name) {
-                Some(target) => {
-                    let target = target.borrow();
-                    target.commands.is_empty()
-                }
-                None => false,
-            }
+            targets
+                .get(name)
+                .map_or(false, |target| target.borrow().commands.is_empty())
         } else {
             false
         };
@@ -585,31 +581,34 @@ impl<'a> Makefile<'a> {
             // targets. If the .s1 suffix is found in .SUFFIXES...
             if self.special_target_has_prereq(".SUFFIXES", &suffix) || suffix.is_empty() {
                 // the inference rules shall be searched in the order defined...
-                'rules: for rule in &self.inference_rules {
+                'rules: for rule in self
+                    .inference_rules
+                    .iter()
                     // for the first .s2.s1 rule...
-                    if rule.product == suffix {
-                        // whose prerequisite file ($*.s2) exists.
-                        let prereq_path =
-                            Path::new(name).with_extension(rule.prereq.trim_start_matches('.'));
-                        let prereq_path_options = if prereq_path.is_absolute() {
-                            vec![prereq_path]
-                        } else {
-                            let mut options = vec![prereq_path.clone()];
-                            options
-                                .extend(vpath_options.iter().map(|vpath| vpath.join(&prereq_path)));
-                            options
-                        };
-                        for prereq in prereq_path_options {
-                            if prereq.exists() {
-                                new_target = Some(Target {
-                                    name: name.into(),
-                                    prerequisites: vec![prereq.to_string_lossy().into()],
-                                    commands: rule.commands.clone(),
-                                    already_updated: Cell::new(false),
-                                });
-                                break 'rules;
+                    .filter(|rule| rule.product == suffix)
+                {
+                    // whose prerequisite file ($*.s2) exists.
+                    let prereq_path =
+                        Path::new(name).with_extension(rule.prereq.trim_start_matches('.'));
+                    if let Some(prereq) = std::iter::once(prereq_path.clone())
+                        .chain(
+                            if prereq_path.is_absolute() {
+                                None
+                            } else {
+                                Some(vpath_options.iter().map(|vpath| vpath.join(&prereq_path)))
                             }
-                        }
+                            .into_iter()
+                            .flatten(),
+                        )
+                        .find(|prereq| prereq.exists())
+                    {
+                        new_target = Some(Target {
+                            name: name.into(),
+                            prerequisites: vec![prereq.to_string_lossy().into()],
+                            commands: rule.commands.clone(),
+                            already_updated: Cell::new(false),
+                        });
+                        break 'rules;
                     }
                 }
             }
-- 
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