clarify when we pass () to functions (clippy::unit_arg)

Author: matthiaskrgr

src/librustc_mir/interpret/eval_context.rs

@@ -581,7 +581,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// If `target` is `None`, that indicates the function cannot return, so we raise UB.
     pub fn return_to_block(&mut self, target: Option<mir::BasicBlock>) -> InterpResult<'tcx> {
         if let Some(target) = target {
-            Ok(self.go_to_block(target))
+            self.go_to_block(target);
+            Ok(())
         } else {
             throw_ub!(Unreachable)
         }

src/librustc_mir/interpret/intrinsics/type_name.rs

@@ -192,7 +192,8 @@ impl PrettyPrinter<'tcx> for AbsolutePathPrinter<'tcx> {
 
 impl Write for AbsolutePathPrinter<'_> {
     fn write_str(&mut self, s: &str) -> std::fmt::Result {
-        Ok(self.path.push_str(s))
+        self.path.push_str(s);
+        Ok(())
     }
 }
 

src/librustc_mir/interpret/terminator.rs

@@ -370,7 +370,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         self.stack.pop();
                         Err(err)
                     }
-                    Ok(v) => Ok(v),
+                    Ok(()) => Ok(()),
                 }
             }
             // cannot use the shim here, because that will only result in infinite recursion

src/librustc_traits/type_op.rs

@@ -80,11 +80,11 @@ impl AscribeUserTypeCx<'me, 'tcx> {
     where
         T: ToTrace<'tcx>,
     {
-        Ok(self
-            .infcx
+        self.infcx
             .at(&ObligationCause::dummy(), self.param_env)
             .relate(a, variance, b)?
-            .into_value_registering_obligations(self.infcx, self.fulfill_cx))
+            .into_value_registering_obligations(self.infcx, self.fulfill_cx);
+        Ok(())
     }
 
     fn prove_predicate(&mut self, predicate: Predicate<'tcx>) {
@@ -165,10 +165,11 @@ fn type_op_eq<'tcx>(
 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
         let (param_env, Eq { a, b }) = key.into_parts();
-        Ok(infcx
+        infcx
             .at(&ObligationCause::dummy(), param_env)
             .eq(a, b)?
-            .into_value_registering_obligations(infcx, fulfill_cx))
+            .into_value_registering_obligations(infcx, fulfill_cx);
+        Ok(())
     })
 }
 
@@ -221,10 +222,11 @@ fn type_op_subtype<'tcx>(
 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
         let (param_env, Subtype { sub, sup }) = key.into_parts();
-        Ok(infcx
+        infcx
             .at(&ObligationCause::dummy(), param_env)
             .sup(sup, sub)?
-            .into_value_registering_obligations(infcx, fulfill_cx))
+            .into_value_registering_obligations(infcx, fulfill_cx);
+        Ok(())
     })
 }