Rollup merge of #70229 - matthiaskrgr:cl3ppy, r=Mark-Simulacrum

more clippy fixes

* remove unused unit values (clippy::unused_unit)
* make some let-if-bindings more idiomatic (clippy::useless_let_if_seq)
* clarify when we pass () to functions (clippy::unit_arg)
* don't redundantly repeat field names (clippy::redundant_field_names)
* remove redundant returns (clippy::needless_return)
* use let instead of match for matches with single bindings (clippy::match_single_binding)
* don't convert results to options just for matching (clippy::if_let_some_result)

src/librustc/ty/layout.rs

@@ -381,12 +381,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         // Field 5 would be the first element, so memory_index is i:
         // Note: if we didn't optimize, it's already right.
 
-        let memory_index;
-        if optimize {
-            memory_index = invert_mapping(&inverse_memory_index);
-        } else {
-            memory_index = inverse_memory_index;
-        }
+        let memory_index =
+            if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
 
         let size = min_size.align_to(align.abi);
         let mut abi = Abi::Aggregate { sized };
@@ -944,33 +940,33 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                             let offset = st[i].fields.offset(field_index) + niche.offset;
                             let size = st[i].size;
 
-                            let mut abi = match st[i].abi {
-                                Abi::Scalar(_) => Abi::Scalar(niche_scalar.clone()),
-                                Abi::ScalarPair(ref first, ref second) => {
-                                    // We need to use scalar_unit to reset the
-                                    // valid range to the maximal one for that
-                                    // primitive, because only the niche is
-                                    // guaranteed to be initialised, not the
-                                    // other primitive.
-                                    if offset.bytes() == 0 {
-                                        Abi::ScalarPair(
-                                            niche_scalar.clone(),
-                                            scalar_unit(second.value),
-                                        )
-                                    } else {
-                                        Abi::ScalarPair(
-                                            scalar_unit(first.value),
-                                            niche_scalar.clone(),
-                                        )
+                            let abi = if st.iter().all(|v| v.abi.is_uninhabited()) {
+                                Abi::Uninhabited
+                            } else {
+                                match st[i].abi {
+                                    Abi::Scalar(_) => Abi::Scalar(niche_scalar.clone()),
+                                    Abi::ScalarPair(ref first, ref second) => {
+                                        // We need to use scalar_unit to reset the
+                                        // valid range to the maximal one for that
+                                        // primitive, because only the niche is
+                                        // guaranteed to be initialised, not the
+                                        // other primitive.
+                                        if offset.bytes() == 0 {
+                                            Abi::ScalarPair(
+                                                niche_scalar.clone(),
+                                                scalar_unit(second.value),
+                                            )
+                                        } else {
+                                            Abi::ScalarPair(
+                                                scalar_unit(first.value),
+                                                niche_scalar.clone(),
+                                            )
+                                        }
                                     }
+                                    _ => Abi::Aggregate { sized: true },
                                 }
-                                _ => Abi::Aggregate { sized: true },
                             };
 
-                            if st.iter().all(|v| v.abi.is_uninhabited()) {
-                                abi = Abi::Uninhabited;
-                            }
-
                             let largest_niche =
                                 Niche::from_scalar(dl, offset, niche_scalar.clone());
 

src/librustc/ty/query/plumbing.rs

@@ -746,7 +746,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// side-effects -- e.g., in order to report errors for erroneous programs.
     ///
     /// Note: The optimization is only available during incr. comp.
-    pub(super) fn ensure_query<Q: QueryDescription<'tcx> + 'tcx>(self, key: Q::Key) -> () {
+    pub(super) fn ensure_query<Q: QueryDescription<'tcx> + 'tcx>(self, key: Q::Key) {
         if Q::EVAL_ALWAYS {
             let _ = self.get_query::<Q>(DUMMY_SP, key);
             return;

src/librustc_builtin_macros/deriving/generic/mod.rs

@@ -1056,8 +1056,9 @@ impl<'a> MethodDef<'a> {
                     self_: field,
                     other: other_fields
                         .iter_mut()
-                        .map(|l| match l.next().unwrap() {
-                            (.., ex, _) => ex,
+                        .map(|l| {
+                            let (.., ex, _) = l.next().unwrap();
+                            ex
                         })
                         .collect(),
                     attrs,

src/librustc_infer/traits/project.rs

@@ -23,7 +23,7 @@ pub type NormalizedTy<'tcx> = Normalized<'tcx, Ty<'tcx>>;
 
 impl<'tcx, T> Normalized<'tcx, T> {
     pub fn with<U>(self, value: U) -> Normalized<'tcx, U> {
-        Normalized { value: value, obligations: self.obligations }
+        Normalized { value, obligations: self.obligations }
     }
 }
 

src/librustc_infer/traits/util.rs

@@ -47,7 +47,7 @@ struct PredicateSet<'tcx> {
 
 impl PredicateSet<'tcx> {
     fn new(tcx: TyCtxt<'tcx>) -> Self {
-        Self { tcx: tcx, set: Default::default() }
+        Self { tcx, set: Default::default() }
     }
 
     fn insert(&mut self, pred: &ty::Predicate<'tcx>) -> bool {

src/librustc_mir/borrow_check/diagnostics/move_errors.rs

@@ -490,17 +490,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 {
                     if pat_snippet.starts_with('&') {
                         let pat_snippet = pat_snippet[1..].trim_start();
-                        let suggestion;
-                        let to_remove;
-                        if pat_snippet.starts_with("mut")
+                        let (suggestion, to_remove) = if pat_snippet.starts_with("mut")
                             && pat_snippet["mut".len()..].starts_with(rustc_lexer::is_whitespace)
                         {
-                            suggestion = pat_snippet["mut".len()..].trim_start();
-                            to_remove = "&mut";
+                            (pat_snippet["mut".len()..].trim_start(), "&mut")
                         } else {
-                            suggestion = pat_snippet;
-                            to_remove = "&";
-                        }
+                            (pat_snippet, "&")
+                        };
                         suggestions.push((pat_span, to_remove, suggestion.to_owned()));
                     }
                 }

src/librustc_mir/const_eval/machine.rs

@@ -335,9 +335,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
     }
 
     #[inline(always)]
-    fn tag_static_base_pointer(_memory_extra: &MemoryExtra, _id: AllocId) -> Self::PointerTag {
-        ()
-    }
+    fn tag_static_base_pointer(_memory_extra: &MemoryExtra, _id: AllocId) -> Self::PointerTag {}
 
     fn box_alloc(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,

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_mir/transform/const_prop.rs

@@ -232,9 +232,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
     }
 
     #[inline(always)]
-    fn tag_static_base_pointer(_memory_extra: &(), _id: AllocId) -> Self::PointerTag {
-        ()
-    }
+    fn tag_static_base_pointer(_memory_extra: &(), _id: AllocId) -> Self::PointerTag {}
 
     fn box_alloc(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,

src/librustc_mir_build/build/expr/as_temp.rs

@@ -73,10 +73,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             // they are never assigned.
             ExprKind::Break { .. } | ExprKind::Continue { .. } | ExprKind::Return { .. } => (),
             ExprKind::Block { body: hir::Block { expr: None, targeted_by_break: false, .. } }
-                if expr_ty.is_never() =>
-            {
-                ()
-            }
+                if expr_ty.is_never() => {}
             _ => {
                 this.cfg
                     .push(block, Statement { source_info, kind: StatementKind::StorageLive(temp) });

src/librustc_mir_build/build/mod.rs

@@ -637,11 +637,12 @@ where
     );
     assert_eq!(block, builder.return_block());
 
-    let mut spread_arg = None;
-    if abi == Abi::RustCall {
+    let spread_arg = if abi == Abi::RustCall {
         // RustCall pseudo-ABI untuples the last argument.
-        spread_arg = Some(Local::new(arguments.len()));
-    }
+        Some(Local::new(arguments.len()))
+    } else {
+        None
+    };
     debug!("fn_id {:?} has attrs {:?}", fn_def_id, tcx.get_attrs(fn_def_id));
 
     let mut body = builder.finish();

src/librustc_resolve/build_reduced_graph.rs

@@ -750,14 +750,16 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 // If this is a tuple or unit struct, define a name
                 // in the value namespace as well.
                 if let Some(ctor_node_id) = vdata.ctor_id() {
-                    let mut ctor_vis = vis;
                     // If the structure is marked as non_exhaustive then lower the visibility
                     // to within the crate.
-                    if vis == ty::Visibility::Public
+                    let mut ctor_vis = if vis == ty::Visibility::Public
                         && attr::contains_name(&item.attrs, sym::non_exhaustive)
                     {
-                        ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
-                    }
+                        ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
+                    } else {
+                        vis
+                    };
+
                     for field in vdata.fields() {
                         // NOTE: The field may be an expansion placeholder, but expansion sets
                         // correct visibilities for unnamed field placeholders specifically, so the
@@ -1166,7 +1168,7 @@ macro_rules! method {
                 visit::$walk(self, node);
             }
         }
-    }
+    };
 }
 
 impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {

src/librustc_span/source_map.rs

@@ -370,11 +370,11 @@ impl SourceMap {
     pub fn doctest_offset_line(&self, file: &FileName, orig: usize) -> usize {
         match file {
             FileName::DocTest(_, offset) => {
-                return if *offset >= 0 {
-                    orig + *offset as usize
-                } else {
+                if *offset < 0 {
                     orig - (-(*offset)) as usize
-                };
+                } else {
+                    orig + *offset as usize
+                }
             }
             _ => orig,
         }

src/librustc_target/spec/apple_base.rs

@@ -57,7 +57,7 @@ pub fn macos_link_env_remove() -> Vec<String> {
     let mut env_remove = Vec::with_capacity(2);
     // Remove the `SDKROOT` environment variable if it's clearly set for the wrong platform, which
     // may occur when we're linking a custom build script while targeting iOS for example.
-    if let Some(sdkroot) = env::var("SDKROOT").ok() {
+    if let Ok(sdkroot) = env::var("SDKROOT") {
         if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("iPhoneSimulator.platform") {
             env_remove.push("SDKROOT".to_string())
         }

src/librustc_target/spec/apple_sdk_base.rs

@@ -43,40 +43,26 @@ pub fn get_sdk_root(sdk_name: &str) -> Result<String, String> {
     // to allow the SDK path to be set. (For clang, xcrun sets
     // SDKROOT; for rustc, the user or build system can set it, or we
     // can fall back to checking for xcrun on PATH.)
-    if let Some(sdkroot) = env::var("SDKROOT").ok() {
+    if let Ok(sdkroot) = env::var("SDKROOT") {
         let p = Path::new(&sdkroot);
         match sdk_name {
             // Ignore `SDKROOT` if it's clearly set for the wrong platform.
             "appletvos"
                 if sdkroot.contains("TVSimulator.platform")
-                    || sdkroot.contains("MacOSX.platform") =>
-            {
-                ()
-            }
+                    || sdkroot.contains("MacOSX.platform") => {}
             "appletvsimulator"
-                if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") =>
-            {
-                ()
-            }
+                if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
             "iphoneos"
                 if sdkroot.contains("iPhoneSimulator.platform")
-                    || sdkroot.contains("MacOSX.platform") =>
-            {
-                ()
-            }
+                    || sdkroot.contains("MacOSX.platform") => {}
             "iphonesimulator"
-                if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") =>
-            {
-                ()
+                if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
             }
             "macosx10.15"
                 if sdkroot.contains("iPhoneOS.platform")
-                    || sdkroot.contains("iPhoneSimulator.platform") =>
-            {
-                ()
-            }
+                    || sdkroot.contains("iPhoneSimulator.platform") => {}
             // Ignore `SDKROOT` if it's not a valid path.
-            _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => (),
+            _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
             _ => return Ok(sdkroot),
         }
     }

src/librustc_trait_selection/traits/select.rs

@@ -2792,7 +2792,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 trait_def_id, trait_obligations
             );
 
-            VtableTraitAliasData { alias_def_id, substs: substs, nested: trait_obligations }
+            VtableTraitAliasData { alias_def_id, substs, nested: trait_obligations }
         })
     }
 

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(())
     })
 }