diff --git a/AK/COWVector.h b/AK/COWVector.h
index 23bc8da0c9d..0b92259773f 100644
--- a/AK/COWVector.h
+++ b/AK/COWVector.h
@@ -110,7 +110,7 @@ public:
             m_detail->m_members.clear();
     }
 
-    T& at(size_t index)
+    T& mutable_at(size_t index)
     {
         // We're handing out a mutable reference, so make sure we own the data exclusively.
         copy();
@@ -122,13 +122,6 @@ public:
         return m_detail->m_members.at(index);
     }
 
-    T& operator[](size_t index)
-    {
-        // We're handing out a mutable reference, so make sure we own the data exclusively.
-        copy();
-        return m_detail->m_members[index];
-    }
-
     T const& operator[](size_t index) const
     {
         return m_detail->m_members[index];
diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index c2205d39ab5..f8bdf1a3c1f 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -332,7 +332,7 @@ ALWAYS_INLINE ExecutionResult OpCode_CheckEnd::execute(MatchInput const& input,
 ALWAYS_INLINE ExecutionResult OpCode_ClearCaptureGroup::execute(MatchInput const& input, MatchState& state) const
 {
     if (input.match_index < state.capture_group_matches.size()) {
-        auto& group = state.capture_group_matches[input.match_index];
+        auto& group = state.capture_group_matches.mutable_at(input.match_index);
         auto group_id = id();
         if (group_id >= group.size())
             group.resize(group_id + 1);
@@ -352,19 +352,19 @@ ALWAYS_INLINE ExecutionResult OpCode_SaveLeftCaptureGroup::execute(MatchInput co
     }
 
     if (id() >= state.capture_group_matches.at(input.match_index).size()) {
-        state.capture_group_matches.at(input.match_index).ensure_capacity(id());
+        state.capture_group_matches.mutable_at(input.match_index).ensure_capacity(id());
         auto capacity = state.capture_group_matches.at(input.match_index).capacity();
         for (size_t i = state.capture_group_matches.at(input.match_index).size(); i <= capacity; ++i)
-            state.capture_group_matches.at(input.match_index).empend();
+            state.capture_group_matches.mutable_at(input.match_index).empend();
     }
 
-    state.capture_group_matches.at(input.match_index).at(id()).left_column = state.string_position;
+    state.capture_group_matches.mutable_at(input.match_index).at(id()).left_column = state.string_position;
     return ExecutionResult::Continue;
 }
 
 ALWAYS_INLINE ExecutionResult OpCode_SaveRightCaptureGroup::execute(MatchInput const& input, MatchState& state) const
 {
-    auto& match = state.capture_group_matches.at(input.match_index).at(id());
+    auto& match = state.capture_group_matches.mutable_at(input.match_index).at(id());
     auto start_position = match.left_column;
     if (state.string_position < start_position) {
         dbgln("Right capture group {} is before left capture group {}!", state.string_position, start_position);
@@ -391,7 +391,7 @@ ALWAYS_INLINE ExecutionResult OpCode_SaveRightCaptureGroup::execute(MatchInput c
 
 ALWAYS_INLINE ExecutionResult OpCode_SaveRightNamedCaptureGroup::execute(MatchInput const& input, MatchState& state) const
 {
-    auto& match = state.capture_group_matches.at(input.match_index).at(id());
+    auto& match = state.capture_group_matches.mutable_at(input.match_index).at(id());
     auto start_position = match.left_column;
     if (state.string_position < start_position)
         return ExecutionResult::Failed_ExecuteLowPrioForks;
@@ -1051,7 +1051,7 @@ ALWAYS_INLINE ExecutionResult OpCode_Repeat::execute(MatchInput const&, MatchSta
 
     if (id() >= state.repetition_marks.size())
         state.repetition_marks.resize(id() + 1);
-    auto& repetition_mark = state.repetition_marks.at(id());
+    auto& repetition_mark = state.repetition_marks.mutable_at(id());
 
     if (repetition_mark == count() - 1) {
         repetition_mark = 0;
@@ -1068,7 +1068,7 @@ ALWAYS_INLINE ExecutionResult OpCode_ResetRepeat::execute(MatchInput const&, Mat
     if (id() >= state.repetition_marks.size())
         state.repetition_marks.resize(id() + 1);
 
-    state.repetition_marks.at(id()) = 0;
+    state.repetition_marks.mutable_at(id()) = 0;
     return ExecutionResult::Continue;
 }
 
diff --git a/Userland/Libraries/LibRegex/RegexMatcher.cpp b/Userland/Libraries/LibRegex/RegexMatcher.cpp
index b4b9910b9e0..e14d04bfecb 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.cpp
+++ b/Userland/Libraries/LibRegex/RegexMatcher.cpp
@@ -157,9 +157,9 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
         for (size_t j = 0; j < c_match_preallocation_count; ++j) {
             state.matches.empend();
             state.capture_group_matches.empend();
-            state.capture_group_matches.at(j).ensure_capacity(capture_groups_count);
+            state.capture_group_matches.mutable_at(j).ensure_capacity(capture_groups_count);
             for (size_t k = 0; k < capture_groups_count; ++k)
-                state.capture_group_matches.at(j).unchecked_append({});
+                state.capture_group_matches.mutable_at(j).unchecked_append({});
         }
     }
 
@@ -169,9 +169,9 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
 
         VERIFY(start_position + state.string_position - start_position <= input.view.length());
         if (input.regex_options.has_flag_set(AllFlags::StringCopyMatches)) {
-            state.matches.at(input.match_index) = { input.view.substring_view(start_position, state.string_position - start_position).to_byte_string(), input.line, start_position, input.global_offset + start_position };
+            state.matches.mutable_at(input.match_index) = { input.view.substring_view(start_position, state.string_position - start_position).to_byte_string(), input.line, start_position, input.global_offset + start_position };
         } else { // let the view point to the original string ...
-            state.matches.at(input.match_index) = { input.view.substring_view(start_position, state.string_position - start_position), input.line, start_position, input.global_offset + start_position };
+            state.matches.mutable_at(input.match_index) = { input.view.substring_view(start_position, state.string_position - start_position), input.line, start_position, input.global_offset + start_position };
         }
     };
 
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Validator.cpp b/Userland/Libraries/LibWasm/AbstractMachine/Validator.cpp
index eb994d49e3f..3795ce2b547 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Validator.cpp
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Validator.cpp
@@ -38,8 +38,7 @@ ErrorOr<void, ValidationError> Validator::validate(Module& module)
     m_context = {};
 
     module.for_each_section_of_type<TypeSection>([this](TypeSection const& section) {
-        for (auto& type : section.types())
-            m_context.types.append(type);
+        m_context.types.extend(section.types());
     });
 
     module.for_each_section_of_type<ImportSection>([&](ImportSection const& section) {