diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index aca3fbbca13..24da75114a6 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -1035,14 +1035,14 @@ pub fn find_transparency(
 pub fn allow_internal_unstable<'a>(
     sess: &'a Session,
     attrs: &'a [Attribute],
-) -> Option<impl Iterator<Item = Symbol> + 'a> {
+) -> impl Iterator<Item = Symbol> + 'a {
     allow_unstable(sess, attrs, sym::allow_internal_unstable)
 }
 
 pub fn rustc_allow_const_fn_unstable<'a>(
     sess: &'a Session,
     attrs: &'a [Attribute],
-) -> Option<impl Iterator<Item = Symbol> + 'a> {
+) -> impl Iterator<Item = Symbol> + 'a {
     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
 }
 
@@ -1050,7 +1050,7 @@ fn allow_unstable<'a>(
     sess: &'a Session,
     attrs: &'a [Attribute],
     symbol: Symbol,
-) -> Option<impl Iterator<Item = Symbol> + 'a> {
+) -> impl Iterator<Item = Symbol> + 'a {
     let attrs = sess.filter_by_name(attrs, symbol);
     let list = attrs
         .filter_map(move |attr| {
@@ -1064,7 +1064,7 @@ fn allow_unstable<'a>(
         })
         .flatten();
 
-    Some(list.into_iter().filter_map(move |it| {
+    list.into_iter().filter_map(move |it| {
         let name = it.ident().map(|ident| ident.name);
         if name.is_none() {
             sess.diagnostic().span_err(
@@ -1073,5 +1073,5 @@ fn allow_unstable<'a>(
             );
         }
         name
-    }))
+    })
 }
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index b0aed812460..f5ae406faec 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -735,7 +735,7 @@ fn execute_work_item<B: ExtraBackendMethods>(
     match work_item {
         WorkItem::Optimize(module) => execute_optimize_work_item(cgcx, module, module_config),
         WorkItem::CopyPostLtoArtifacts(module) => {
-            execute_copy_from_cache_work_item(cgcx, module, module_config)
+            Ok(execute_copy_from_cache_work_item(cgcx, module, module_config))
         }
         WorkItem::LTO(module) => execute_lto_work_item(cgcx, module, module_config),
     }
@@ -844,7 +844,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     module: CachedModuleCodegen,
     module_config: &ModuleConfig,
-) -> Result<WorkItemResult<B>, FatalError> {
+) -> WorkItemResult<B> {
     let incr_comp_session_dir = cgcx.incr_comp_session_dir.as_ref().unwrap();
     let mut object = None;
     if let Some(saved_file) = module.source.saved_file {
@@ -870,13 +870,13 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
     assert_eq!(object.is_some(), module_config.emit_obj != EmitObj::None);
 
-    Ok(WorkItemResult::Compiled(CompiledModule {
+    WorkItemResult::Compiled(CompiledModule {
         name: module.name,
         kind: ModuleKind::Regular,
         object,
         dwarf_object: None,
         bytecode: None,
-    }))
+    })
 }
 
 fn execute_lto_work_item<B: ExtraBackendMethods>(
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index e3dc793a7fa..ca304c05cdc 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -756,8 +756,8 @@ impl SyntaxExtension {
         name: Symbol,
         attrs: &[ast::Attribute],
     ) -> SyntaxExtension {
-        let allow_internal_unstable = attr::allow_internal_unstable(sess, &attrs)
-            .map(|features| features.collect::<Vec<Symbol>>().into());
+        let allow_internal_unstable =
+            Some(attr::allow_internal_unstable(sess, &attrs).collect::<Vec<Symbol>>().into());
 
         let mut local_inner_macros = false;
         if let Some(macro_export) = sess.find_by_name(attrs, sym::macro_export) {
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 5ebe38b2d7e..449b3a82dcb 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -266,7 +266,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         let range = self.check_bounds(ptr.offset, size);
 
         self.mark_init(ptr, size, true);
-        self.clear_relocations(cx, ptr, size)?;
+        self.clear_relocations(cx, ptr, size);
 
         AllocationExtra::memory_written(self, ptr, size)?;
 
@@ -484,18 +484,13 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
     /// uninitialized. This is a somewhat odd "spooky action at a distance",
     /// but it allows strictly more code to run than if we would just error
     /// immediately in that case.
-    fn clear_relocations(
-        &mut self,
-        cx: &impl HasDataLayout,
-        ptr: Pointer<Tag>,
-        size: Size,
-    ) -> InterpResult<'tcx> {
+    fn clear_relocations(&mut self, cx: &impl HasDataLayout, ptr: Pointer<Tag>, size: Size) {
         // Find the start and end of the given range and its outermost relocations.
         let (first, last) = {
             // Find all relocations overlapping the given range.
             let relocations = self.get_relocations(cx, ptr, size);
             if relocations.is_empty() {
-                return Ok(());
+                return;
             }
 
             (
@@ -517,8 +512,6 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
 
         // Forget all the relocations.
         self.relocations.remove_range(first..last);
-
-        Ok(())
     }
 
     /// Errors if there are relocations overlapping with the edges of the
diff --git a/compiler/rustc_mir/src/interpret/intrinsics.rs b/compiler/rustc_mir/src/interpret/intrinsics.rs
index c4039f2f15e..d36b3a7d9b5 100644
--- a/compiler/rustc_mir/src/interpret/intrinsics.rs
+++ b/compiler/rustc_mir/src/interpret/intrinsics.rs
@@ -23,11 +23,7 @@ use super::{
 mod caller_location;
 mod type_name;
 
-fn numeric_intrinsic<'tcx, Tag>(
-    name: Symbol,
-    bits: u128,
-    kind: Primitive,
-) -> InterpResult<'tcx, Scalar<Tag>> {
+fn numeric_intrinsic<Tag>(name: Symbol, bits: u128, kind: Primitive) -> Scalar<Tag> {
     let size = match kind {
         Primitive::Int(integer, _) => integer.size(),
         _ => bug!("invalid `{}` argument: {:?}", name, bits),
@@ -41,7 +37,7 @@ fn numeric_intrinsic<'tcx, Tag>(
         sym::bitreverse => (bits << extra).reverse_bits(),
         _ => bug!("not a numeric intrinsic: {}", name),
     };
-    Ok(Scalar::from_uint(bits_out, size))
+    Scalar::from_uint(bits_out, size)
 }
 
 /// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated
@@ -208,7 +204,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 if nonzero && bits == 0 {
                     throw_ub_format!("`{}_nonzero` called on 0", intrinsic_name);
                 }
-                let out_val = numeric_intrinsic(intrinsic_name, bits, kind)?;
+                let out_val = numeric_intrinsic(intrinsic_name, bits, kind);
                 self.write_scalar(out_val, dest)?;
             }
             sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
diff --git a/compiler/rustc_mir/src/transform/check_consts/mod.rs b/compiler/rustc_mir/src/transform/check_consts/mod.rs
index ba7bea4ac54..19aee033a69 100644
--- a/compiler/rustc_mir/src/transform/check_consts/mod.rs
+++ b/compiler/rustc_mir/src/transform/check_consts/mod.rs
@@ -85,8 +85,7 @@ pub fn rustc_allow_const_fn_unstable(
     feature_gate: Symbol,
 ) -> bool {
     let attrs = tcx.get_attrs(def_id);
-    attr::rustc_allow_const_fn_unstable(&tcx.sess, attrs)
-        .map_or(false, |mut features| features.any(|name| name == feature_gate))
+    attr::rustc_allow_const_fn_unstable(&tcx.sess, attrs).any(|name| name == feature_gate)
 }
 
 // Returns `true` if the given `const fn` is "const-stable".
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index fa05df6805f..28bfaea4555 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -426,7 +426,7 @@ impl<'a> Parser<'a> {
         let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
         let limits =
             if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
-        Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
+        Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits), AttrVec::new()))
     }
 
     fn is_at_start_of_range_notation_rhs(&self) -> bool {
@@ -474,7 +474,7 @@ impl<'a> Parser<'a> {
             } else {
                 (lo, None)
             };
-            Ok(this.mk_expr(span, this.mk_range(None, opt_end, limits)?, attrs.into()))
+            Ok(this.mk_expr(span, this.mk_range(None, opt_end, limits), attrs.into()))
         })
     }
 
@@ -1041,7 +1041,7 @@ impl<'a> Parser<'a> {
     /// Assuming we have just parsed `.`, continue parsing into an expression.
     fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
         if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
-            return self.mk_await_expr(self_arg, lo);
+            return Ok(self.mk_await_expr(self_arg, lo));
         }
 
         let fn_span_lo = self.token.span;
@@ -2396,12 +2396,12 @@ impl<'a> Parser<'a> {
         start: Option<P<Expr>>,
         end: Option<P<Expr>>,
         limits: RangeLimits,
-    ) -> PResult<'a, ExprKind> {
+    ) -> ExprKind {
         if end.is_none() && limits == RangeLimits::Closed {
             self.error_inclusive_range_with_no_end(self.prev_token.span);
-            Ok(ExprKind::Err)
+            ExprKind::Err
         } else {
-            Ok(ExprKind::Range(start, end, limits))
+            ExprKind::Range(start, end, limits)
         }
     }
 
@@ -2421,11 +2421,11 @@ impl<'a> Parser<'a> {
         ExprKind::Call(f, args)
     }
 
-    fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+    fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
         let span = lo.to(self.prev_token.span);
         let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
         self.recover_from_await_method_call();
-        Ok(await_expr)
+        await_expr
     }
 
     crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 0f907859a19..f3f5fc9af64 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1679,7 +1679,7 @@ impl<'a> Parser<'a> {
         let constness = self.parse_constness();
         let asyncness = self.parse_asyncness();
         let unsafety = self.parse_unsafety();
-        let ext = self.parse_extern()?;
+        let ext = self.parse_extern();
 
         if let Async::Yes { span, .. } = asyncness {
             self.ban_async_in_2015(span);
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index ace4134b1f6..1292286bc18 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1202,12 +1202,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses `extern string_literal?`.
-    fn parse_extern(&mut self) -> PResult<'a, Extern> {
-        Ok(if self.eat_keyword(kw::Extern) {
-            Extern::from_abi(self.parse_abi())
-        } else {
-            Extern::None
-        })
+    fn parse_extern(&mut self) -> Extern {
+        if self.eat_keyword(kw::Extern) { Extern::from_abi(self.parse_abi()) } else { Extern::None }
     }
 
     /// Parses a string literal as an ABI spec.
diff --git a/compiler/rustc_passes/src/check_const.rs b/compiler/rustc_passes/src/check_const.rs
index 9328f7cd9ec..da713566c31 100644
--- a/compiler/rustc_passes/src/check_const.rs
+++ b/compiler/rustc_passes/src/check_const.rs
@@ -106,7 +106,7 @@ impl<'tcx> CheckConstVisitor<'tcx> {
             // However, we cannot allow stable `const fn`s to use unstable features without an explicit
             // opt-in via `rustc_allow_const_fn_unstable`.
             attr::rustc_allow_const_fn_unstable(&tcx.sess, &tcx.get_attrs(def_id))
-                .map_or(false, |mut features| features.any(|name| name == feature_gate))
+                .any(|name| name == feature_gate)
         };
 
         match required_gates {