feat(css/parser): Add legacy_ie to the ParserConfig

crates/swc_css_parser/src/parser/mod.rs

@@ -47,6 +47,10 @@ pub struct ParserConfig {
     /// Defaults to `false`.
     #[serde(default)]
     pub legacy_nesting: bool,
+
+    /// If this is `true`, the legacy syntax for IE will be parsed.
+    #[serde(default)]
+    pub legacy_ie: bool,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]

crates/swc_css_parser/src/parser/values_and_units/mod.rs

@@ -1704,7 +1704,7 @@ where
                 let value = match self.try_parse(|p| p.parse_generic_value()) {
                     Some(v) => v,
                     None => {
-                        if is_one_of!(self, ";", ":") {
+                        if is_one_of!(self, ";", ":") || (self.config.legacy_ie && is!(self, "=")) {
                             let tok = self.input.bump().unwrap();
 
                             ComponentValue::PreservedToken(Box::new(tok))

crates/swc_css_parser/tests/fixture/turbo/4092/input.css

@@ -0,0 +1,4 @@
+.carousel .control-dots .dot.selected, .carousel .control-dots .dot:hover {
+     opacity: 1;
+     filter: alpha(opacity=100);
+}