Make Ok value of repeat_while_none more general

Author: spastorino

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -485,35 +485,38 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         mut goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
     ) -> Result<Certainty, NoSolution> {
         let mut new_goals = Vec::new();
-        self.repeat_while_none(|this| {
-            let mut has_changed = Err(Certainty::Yes);
-            for goal in goals.drain(..) {
-                let (changed, certainty) = match this.evaluate_goal(goal) {
-                    Ok(result) => result,
-                    Err(NoSolution) => return Some(Err(NoSolution)),
-                };
-
-                if changed {
-                    has_changed = Ok(());
-                }
+        self.repeat_while_none(
+            |_| Certainty::Maybe(MaybeCause::Overflow),
+            |this| {
+                let mut has_changed = Err(Certainty::Yes);
+                for goal in goals.drain(..) {
+                    let (changed, certainty) = match this.evaluate_goal(goal) {
+                        Ok(result) => result,
+                        Err(NoSolution) => return Some(Err(NoSolution)),
+                    };
+
+                    if changed {
+                        has_changed = Ok(());
+                    }
 
-                match certainty {
-                    Certainty::Yes => {}
-                    Certainty::Maybe(_) => {
-                        new_goals.push(goal);
-                        has_changed = has_changed.map_err(|c| c.unify_and(certainty));
+                    match certainty {
+                        Certainty::Yes => {}
+                        Certainty::Maybe(_) => {
+                            new_goals.push(goal);
+                            has_changed = has_changed.map_err(|c| c.unify_and(certainty));
+                        }
                     }
                 }
-            }
 
-            match has_changed {
-                Ok(()) => {
-                    mem::swap(&mut new_goals, &mut goals);
-                    None
+                match has_changed {
+                    Ok(()) => {
+                        mem::swap(&mut new_goals, &mut goals);
+                        None
+                    }
+                    Err(certainty) => Some(Ok(certainty)),
                 }
-                Err(certainty) => Some(Ok(certainty)),
-            }
-        })
+            },
+        )
     }
 
     // Recursively evaluates a list of goals to completion, making a query response.

compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs

@@ -63,10 +63,11 @@ impl<'tcx> SearchGraph<'tcx> {
 
 impl<'tcx> EvalCtxt<'_, 'tcx> {
     /// A `while`-loop which tracks overflow.
-    pub fn repeat_while_none(
+    pub fn repeat_while_none<T>(
         &mut self,
-        mut loop_body: impl FnMut(&mut Self) -> Option<Result<Certainty, NoSolution>>,
-    ) -> Result<Certainty, NoSolution> {
+        mut overflow_body: impl FnMut(&mut Self) -> T,
+        mut loop_body: impl FnMut(&mut Self) -> Option<Result<T, NoSolution>>,
+    ) -> Result<T, NoSolution> {
         let start_depth = self.search_graph.overflow_data.additional_depth;
         let depth = self.search_graph.stack.len();
         while !self.search_graph.overflow_data.has_overflow(depth) {
@@ -79,6 +80,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         }
         self.search_graph.overflow_data.additional_depth = start_depth;
         self.search_graph.overflow_data.deal_with_overflow();
-        Ok(Certainty::Maybe(MaybeCause::Overflow))
+        Ok(overflow_body(self))
     }
 }