diff --git a/servo/components/style/values/animated/mod.rs b/servo/components/style/values/animated/mod.rs
index e487773ccfb7d..539b03a54078f 100644
--- a/servo/components/style/values/animated/mod.rs
+++ b/servo/components/style/values/animated/mod.rs
@@ -883,9 +883,9 @@ corresponding
 /
 match
 arm
-is
-not
-generated
+returns
+an
+error
 .
 /
 /
diff --git a/servo/components/style/values/distance.rs b/servo/components/style/values/distance.rs
index 9856544b70094..b0798833109e4 100644
--- a/servo/components/style/values/distance.rs
+++ b/servo/components/style/values/distance.rs
@@ -195,9 +195,9 @@ corresponding
 /
 match
 arm
-is
-not
-generated
+returns
+an
+error
 .
 /
 /
diff --git a/servo/components/style_derive/animate.rs b/servo/components/style_derive/animate.rs
index d5033d2e13cb9..aaf204caeaaa5 100644
--- a/servo/components/style_derive/animate.rs
+++ b/servo/components/style_derive/animate.rs
@@ -133,6 +133,23 @@ input
 )
 ;
 let
+input_attrs
+=
+cg
+:
+:
+parse_input_attrs
+:
+:
+<
+AnimateInputAttrs
+>
+(
+&
+input
+)
+;
+let
 no_bound
 =
 animation_input_attrs
@@ -225,7 +242,7 @@ let
 (
 mut
 match_body
-append_error_clause
+needs_catchall_branch
 )
 =
 {
@@ -242,8 +259,7 @@ input
 )
 ;
 let
-mut
-append_error_clause
+needs_catchall_branch
 =
 s
 .
@@ -284,7 +300,6 @@ variant
 let
 arm
 =
-match
 derive_variant_arm
 (
 variant
@@ -292,31 +307,6 @@ variant
 mut
 where_clause
 )
-{
-Ok
-(
-arm
-)
-=
->
-arm
-Err
-(
-(
-)
-)
-=
->
-{
-append_error_clause
-=
-true
-;
-return
-body
-;
-}
-}
 ;
 quote
 !
@@ -331,7 +321,7 @@ arm
 ;
 (
 match_body
-append_error_clause
+needs_catchall_branch
 )
 }
 ;
@@ -344,36 +334,38 @@ where_clause
 where_clause
 ;
 if
-append_error_clause
+needs_catchall_branch
 {
-let
-input_attrs
-=
-cg
-:
-:
-parse_input_attrs
-:
+/
+/
+This
+ideally
+shouldn
+'
+t
+be
+needed
+but
+see
+/
+/
+https
 :
-<
-AnimateInputAttrs
->
-(
-&
-input
-)
-;
-if
-let
-Some
-(
-fallback
-)
-=
-input_attrs
+/
+/
+github
 .
-fallback
-{
+com
+/
+rust
+-
+lang
+/
+rust
+/
+issues
+/
+68867
 match_body
 .
 append_all
@@ -381,45 +373,20 @@ append_all
 quote
 !
 {
-(
-this
-other
-)
+_
 =
 >
-#
-fallback
-(
-this
-other
-procedure
-)
-}
-)
-;
-}
-else
+unsafe
 {
-match_body
-.
-append_all
-(
-quote
+debug_unreachable
 !
-{
-_
-=
->
-Err
-(
 (
 )
-)
+}
 }
 )
 ;
 }
-}
 let
 name
 =
@@ -443,6 +410,45 @@ split_for_impl
 (
 )
 ;
+let
+fallback
+=
+match
+input_attrs
+.
+fallback
+{
+Some
+(
+fallback
+)
+=
+>
+quote
+!
+{
+#
+fallback
+(
+self
+other
+procedure
+)
+}
+None
+=
+>
+quote
+!
+{
+Err
+(
+(
+)
+)
+}
+}
+;
 quote
 !
 {
@@ -510,6 +516,35 @@ Self
 )
 >
 {
+if
+std
+:
+:
+mem
+:
+:
+discriminant
+(
+self
+)
+!
+=
+std
+:
+:
+mem
+:
+:
+discriminant
+(
+other
+)
+{
+return
+#
+fallback
+;
+}
 match
 (
 self
@@ -541,12 +576,7 @@ WhereClause
 )
 -
 >
-Result
-<
 TokenStream
-(
-)
->
 {
 let
 variant_attrs
@@ -569,19 +599,6 @@ ast
 )
 )
 ;
-if
-variant_attrs
-.
-error
-{
-return
-Err
-(
-(
-)
-)
-;
-}
 let
 (
 this_pattern
@@ -618,6 +635,33 @@ other
 "
 )
 ;
+if
+variant_attrs
+.
+error
+{
+return
+quote
+!
+{
+(
+&
+#
+this_pattern
+&
+#
+other_pattern
+)
+=
+>
+Err
+(
+(
+)
+)
+}
+;
+}
 let
 (
 result_value
@@ -833,8 +877,6 @@ procedure
 )
 )
 ;
-Ok
-(
 quote
 !
 {
@@ -858,7 +900,6 @@ result_value
 )
 }
 }
-)
 }
 #
 [
diff --git a/servo/components/style_derive/compute_squared_distance.rs b/servo/components/style_derive/compute_squared_distance.rs
index cc2dd50796c3b..7883dff929f27 100644
--- a/servo/components/style_derive/compute_squared_distance.rs
+++ b/servo/components/style_derive/compute_squared_distance.rs
@@ -94,6 +94,7 @@ syn
 {
 DeriveInput
 Path
+WhereClause
 }
 ;
 use
@@ -130,6 +131,23 @@ input
 )
 ;
 let
+input_attrs
+=
+cg
+:
+:
+parse_input_attrs
+:
+:
+<
+DistanceInputAttrs
+>
+(
+&
+input
+)
+;
+let
 no_bound
 =
 animation_input_attrs
@@ -222,7 +240,7 @@ let
 (
 mut
 match_body
-append_error_clause
+needs_catchall_branch
 )
 =
 {
@@ -242,8 +260,7 @@ input
 )
 ;
 let
-mut
-append_error_clause
+needs_catchall_branch
 =
 s
 .
@@ -282,7 +299,289 @@ variant
 |
 {
 let
-attrs
+arm
+=
+derive_variant_arm
+(
+variant
+&
+mut
+where_clause
+)
+;
+quote
+!
+{
+#
+body
+#
+arm
+}
+}
+)
+;
+(
+match_body
+needs_catchall_branch
+)
+}
+;
+input
+.
+generics
+.
+where_clause
+=
+where_clause
+;
+if
+needs_catchall_branch
+{
+/
+/
+This
+ideally
+shouldn
+'
+t
+be
+needed
+but
+see
+:
+/
+/
+https
+:
+/
+/
+github
+.
+com
+/
+rust
+-
+lang
+/
+rust
+/
+issues
+/
+68867
+match_body
+.
+append_all
+(
+quote
+!
+{
+_
+=
+>
+unsafe
+{
+debug_unreachable
+!
+(
+)
+}
+}
+)
+;
+}
+let
+fallback
+=
+match
+input_attrs
+.
+fallback
+{
+Some
+(
+fallback
+)
+=
+>
+quote
+!
+{
+#
+fallback
+(
+self
+other
+)
+}
+None
+=
+>
+quote
+!
+{
+Err
+(
+(
+)
+)
+}
+}
+;
+let
+name
+=
+&
+input
+.
+ident
+;
+let
+(
+impl_generics
+ty_generics
+where_clause
+)
+=
+input
+.
+generics
+.
+split_for_impl
+(
+)
+;
+quote
+!
+{
+impl
+#
+impl_generics
+crate
+:
+:
+values
+:
+:
+distance
+:
+:
+ComputeSquaredDistance
+for
+#
+name
+#
+ty_generics
+#
+where_clause
+{
+#
+[
+allow
+(
+unused_variables
+unused_imports
+)
+]
+#
+[
+inline
+]
+fn
+compute_squared_distance
+(
+&
+self
+other
+:
+&
+Self
+)
+-
+>
+Result
+<
+crate
+:
+:
+values
+:
+:
+distance
+:
+:
+SquaredDistance
+(
+)
+>
+{
+if
+std
+:
+:
+mem
+:
+:
+discriminant
+(
+self
+)
+!
+=
+std
+:
+:
+mem
+:
+:
+discriminant
+(
+other
+)
+{
+return
+#
+fallback
+;
+}
+match
+(
+self
+other
+)
+{
+#
+match_body
+}
+}
+}
+}
+}
+fn
+derive_variant_arm
+(
+variant
+:
+&
+synstructure
+:
+:
+VariantInfo
+mut
+where_clause
+:
+&
+mut
+Option
+<
+WhereClause
+>
+)
+-
+>
+TokenStream
+{
+let
+variant_attrs
 =
 cg
 :
@@ -302,19 +601,6 @@ ast
 )
 )
 ;
-if
-attrs
-.
-error
-{
-append_error_clause
-=
-true
-;
-return
-body
-;
-}
 let
 (
 this_pattern
@@ -351,6 +637,33 @@ other
 "
 )
 ;
+if
+variant_attrs
+.
+error
+{
+return
+quote
+!
+{
+(
+&
+#
+this_pattern
+&
+#
+other_pattern
+)
+=
+>
+Err
+(
+(
+)
+)
+}
+;
+}
 let
 sum
 =
@@ -590,11 +903,10 @@ quote
 sum
 }
 ;
+return
 quote
 !
 {
-#
-body
 (
 &
 #
@@ -605,206 +917,13 @@ other_pattern
 )
 =
 >
-{
 Ok
 (
 #
 sum
 )
 }
-}
-}
-)
 ;
-(
-match_body
-append_error_clause
-)
-}
-;
-input
-.
-generics
-.
-where_clause
-=
-where_clause
-;
-if
-append_error_clause
-{
-let
-input_attrs
-=
-cg
-:
-:
-parse_input_attrs
-:
-:
-<
-DistanceInputAttrs
->
-(
-&
-input
-)
-;
-if
-let
-Some
-(
-fallback
-)
-=
-input_attrs
-.
-fallback
-{
-match_body
-.
-append_all
-(
-quote
-!
-{
-(
-this
-other
-)
-=
->
-#
-fallback
-(
-this
-other
-)
-}
-)
-;
-}
-else
-{
-match_body
-.
-append_all
-(
-quote
-!
-{
-_
-=
->
-Err
-(
-(
-)
-)
-}
-)
-;
-}
-}
-let
-name
-=
-&
-input
-.
-ident
-;
-let
-(
-impl_generics
-ty_generics
-where_clause
-)
-=
-input
-.
-generics
-.
-split_for_impl
-(
-)
-;
-quote
-!
-{
-impl
-#
-impl_generics
-crate
-:
-:
-values
-:
-:
-distance
-:
-:
-ComputeSquaredDistance
-for
-#
-name
-#
-ty_generics
-#
-where_clause
-{
-#
-[
-allow
-(
-unused_variables
-unused_imports
-)
-]
-#
-[
-inline
-]
-fn
-compute_squared_distance
-(
-&
-self
-other
-:
-&
-Self
-)
--
->
-Result
-<
-crate
-:
-:
-values
-:
-:
-distance
-:
-:
-SquaredDistance
-(
-)
->
-{
-match
-(
-self
-other
-)
-{
-#
-match_body
-}
-}
-}
-}
 }
 #
 [