diff --git a/crates/compiler/src/lexer.rs b/crates/compiler/src/lexer.rs
index 6d8fbda..0f8a52c 100644
--- a/crates/compiler/src/lexer.rs
+++ b/crates/compiler/src/lexer.rs
@@ -119,6 +119,7 @@ pub(crate) struct TokenLexer<'a> {
     cursor: u32,
 }
 
+// todo: maybe char indices?
 impl<'a> TokenLexer<'a> {
     pub fn new(buf: Peekable<Chars<'a>>) -> TokenLexer<'a> {
         Self { buf, cursor: 0 }
diff --git a/crates/compiler/src/selector/complex.rs b/crates/compiler/src/selector/complex.rs
index dd8be40..801e86b 100644
--- a/crates/compiler/src/selector/complex.rs
+++ b/crates/compiler/src/selector/complex.rs
@@ -5,6 +5,8 @@ use std::{
     sync::atomic::{AtomicU32, Ordering as AtomicOrdering},
 };
 
+use codemap::Span;
+
 use crate::error::SassResult;
 
 use super::{CompoundSelector, Pseudo, SelectorList, SimpleSelector, Specificity};
@@ -323,10 +325,11 @@ impl ComplexSelectorComponent {
 
     pub fn resolve_parent_selectors(
         self,
+        span: Span,
         parent: SelectorList,
     ) -> SassResult<Option<Vec<ComplexSelector>>> {
         match self {
-            Self::Compound(c) => c.resolve_parent_selectors(parent),
+            Self::Compound(c) => c.resolve_parent_selectors(span, parent),
             Self::Combinator(..) => todo!(),
         }
     }
diff --git a/crates/compiler/src/selector/compound.rs b/crates/compiler/src/selector/compound.rs
index 3264fb1..d5e852b 100644
--- a/crates/compiler/src/selector/compound.rs
+++ b/crates/compiler/src/selector/compound.rs
@@ -1,5 +1,7 @@
 use std::fmt::{self, Write};
 
+use codemap::Span;
+
 use crate::error::SassResult;
 
 use super::{
@@ -106,6 +108,7 @@ impl CompoundSelector {
     /// Returns `None` if `compound` doesn't contain any `SimpleSelector::Parent`s.
     pub fn resolve_parent_selectors(
         self,
+        span: Span,
         parent: SelectorList,
     ) -> SassResult<Option<Vec<ComplexSelector>>> {
         let contains_selector_pseudo = self.components.iter().any(|simple| {
@@ -163,7 +166,7 @@ impl CompoundSelector {
             )]));
         }
 
-        let span = parent.span;
+        let parent_span = parent.span;
 
         Ok(Some(
             parent
@@ -185,7 +188,7 @@ impl CompoundSelector {
 
                     if let Some(SimpleSelector::Parent(Some(suffix))) = self.components.first() {
                         let mut end = components.pop().unwrap();
-                        end.add_suffix(suffix, span)?;
+                        end.add_suffix(suffix, parent_span)?;
                         components.push(end);
                     }
 
diff --git a/crates/compiler/src/selector/list.rs b/crates/compiler/src/selector/list.rs
index de893ba..ff59b35 100644
--- a/crates/compiler/src/selector/list.rs
+++ b/crates/compiler/src/selector/list.rs
@@ -206,7 +206,7 @@ impl SelectorList {
                             if component.is_compound() {
                                 let resolved = match component
                                     .clone()
-                                    .resolve_parent_selectors(parent.clone())?
+                                    .resolve_parent_selectors(self.span, parent.clone())?
                                 {
                                     Some(r) => r,
                                     None => {
diff --git a/crates/lib/tests/is-superselector.rs b/crates/lib/tests/is-superselector.rs
index 6da02d5..4ca8d79 100644
--- a/crates/lib/tests/is-superselector.rs
+++ b/crates/lib/tests/is-superselector.rs
@@ -469,6 +469,11 @@ test!(
     "a {\n  color: is-superselector(\"::-pfx-slotted(c d, e f)\", \"::-pfx-slotted(c d, e f)\");\n}\n",
     "a {\n  color: true;\n}\n"
 );
+test!(
+    other_complex_ends_in_combinator,
+    "a {\n  color: is-superselector(\"a > b\", \"a >\");\n}\n",
+    "a {\n  color: false;\n}\n"
+);
 
 // todo: /spec/core_functions/selector/is_superselector/simple/pseudo/selector_arg/
 // :not, :matches, :nth-child, :nth-last-child
diff --git a/crates/lib/tests/list.rs b/crates/lib/tests/list.rs
index 7c5a9e1..c68a358 100644
--- a/crates/lib/tests/list.rs
+++ b/crates/lib/tests/list.rs
@@ -478,6 +478,22 @@ test!(
     }",
     "a {\n  color: true;\n}\n"
 );
+test!(
+    list_separator_slash,
+    "@use 'sass:list';
+    a {
+        color: list-separator(list.slash(a, b));
+    }",
+    "a {\n  color: slash;\n}\n"
+);
+test!(
+    list_slash,
+    "@use 'sass:list';
+    a {
+        color: list.slash(a, b, c);
+    }",
+    "a {\n  color: a / b / c;\n}\n"
+);
 error!(
     nth_list_index_0,
     "a {\n  color: nth(a b c, 0);\n}\n", "Error: $n: List index may not be 0."
diff --git a/crates/lib/tests/plain-css.rs b/crates/lib/tests/plain-css.rs
index c3ad180..069def7 100644
--- a/crates/lib/tests/plain-css.rs
+++ b/crates/lib/tests/plain-css.rs
@@ -195,6 +195,14 @@ error!(
     "Error: Interpolation isn't allowed in plain CSS.",
     grass::Options::default().input_syntax(InputSyntax::Css)
 );
+error!(
+    disallows_placeholder_selector,
+    "%a {
+        color: red;
+    }",
+    "Error: Placeholder selectors aren't allowed here.",
+    grass::Options::default().input_syntax(InputSyntax::Css)
+);
 test!(
     allows_rgb_function,
     "a {
diff --git a/crates/lib/tests/selector-append.rs b/crates/lib/tests/selector-append.rs
index 2a48e70..6594cb5 100644
--- a/crates/lib/tests/selector-append.rs
+++ b/crates/lib/tests/selector-append.rs
@@ -74,3 +74,7 @@ error!(
     "a {\n  color: selector-append();\n}\n",
     "Error: $selectors: At least one selector must be passed."
 );
+error!(
+    append_two_type_selectors_with_namespace,
+    "a {\n  color: selector-append(\"a|a\", \"a|a\");\n}\n", "Error: Can't append a|a to a|a."
+);
diff --git a/crates/lib/tests/selector-nest.rs b/crates/lib/tests/selector-nest.rs
index 470c61e..5353643 100644
--- a/crates/lib/tests/selector-nest.rs
+++ b/crates/lib/tests/selector-nest.rs
@@ -131,6 +131,16 @@ test!(
     "a {\n  color: selector-nest(\"c\", (d, e f));\n}\n",
     "a {\n  color: c d, c e f;\n}\n"
 );
+test!(
+    double_nested_parent_selector_inside_psuedo_class,
+    "a {\n  color: selector-nest(\"a\", \":matches(&:not(&))\");\n}\n",
+    "a {\n  color: :matches(a:not(a));\n}\n"
+);
+test!(
+    double_nested_parent_selector_inside_psuedo_class_as_part_of_complex,
+    "a {\n  color: selector-nest(\"a\", \":not(&):matches(:not(a))\");\n}\n",
+    "a {\n  color: :not(a):matches(:not(a));\n}\n"
+);
 error!(
     #[ignore = "https://github.com/sass/dart-sass/issues/966"]
     disallows_parent_selector_as_first_arg,
@@ -169,3 +179,8 @@ error!(
     "a {\n  color: selector-nest();\n}\n",
     "Error: $selectors: At least one selector must be passed."
 );
+error!(
+    parent_ends_with_combinator_and_child_has_parent_selector_as_pseudo_element,
+    "a {\n  color: selector-nest(\"a >\", \":matches(&c)\");\n}\n",
+    "Error: Parent \"a >\" is incompatible with this selector."
+);
diff --git a/crates/lib/tests/selector-parse.rs b/crates/lib/tests/selector-parse.rs
index 4d8cc22..a410bf8 100644
--- a/crates/lib/tests/selector-parse.rs
+++ b/crates/lib/tests/selector-parse.rs
@@ -101,6 +101,11 @@ test!(
     "a {\n  color: selector-parse(\"b c, d e, f g\");\n}\n",
     "a {\n  color: b c, d e, f g;\n}\n"
 );
+test!(
+    not_pseudo_invisible,
+    "a {\n  color: selector-parse(\":not(%a)\");\n}\n",
+    "a {\n  color: *;\n}\n"
+);
 error!(
     invalid_selector,
     "a {\n  color: selector-parse(\"!!!!!!!!\");\n}\n", "Error: $selector: expected selector."
diff --git a/crates/lib/tests/selector-unify.rs b/crates/lib/tests/selector-unify.rs
index c7062c6..02f89b8 100644
--- a/crates/lib/tests/selector-unify.rs
+++ b/crates/lib/tests/selector-unify.rs
@@ -678,3 +678,13 @@ test!(
     "a {\n  color: selector-unify(\":is(.c)\", \":is(.d)\");\n}\n",
     "a {\n  color: :is(.c):is(.d);\n}\n"
 );
+test!(
+    universal_and_class,
+    "a {\n  color: selector-unify(\"*\", \".a\");\n}\n",
+    "a {\n  color: .a;\n}\n"
+);
+test!(
+    universal_and_psuedo,
+    "a {\n  color: selector-unify(\"*\", \":a\");\n}\n",
+    "a {\n  color: :a;\n}\n"
+);
diff --git a/crates/lib/tests/selectors.rs b/crates/lib/tests/selectors.rs
index 40fcdbf..7bb84fb 100644
--- a/crates/lib/tests/selectors.rs
+++ b/crates/lib/tests/selectors.rs
@@ -971,9 +971,17 @@ error!(
     ":nth-child(even#) {\n  color: &;\n}\n", "Error: expected \")\"."
 );
 error!(
-    a_n_plus_b_n_nothing_after_plus,
+    a_n_plus_b_n_double_nothing_after_plus,
     ":nth-child:nth-child(n+{}", "Error: Expected a number."
 );
+error!(
+    a_n_plus_b_n_nothing_after_plus,
+    ":nth-child(n+{}", "Error: Expected a number."
+);
+error!(
+    a_n_plus_b_n_non_numeric_after_plus,
+    ":nth-child(n+b) {}", "Error: Expected a number."
+);
 error!(nothing_after_period, ". {}", "Error: Expected identifier.");
 error!(nothing_after_hash, "# {}", "Error: Expected identifier.");
 error!(nothing_after_percent, "% {}", "Error: Expected identifier.");