better handle strings passed to special css functions

src/parse/ident.rs

@@ -248,7 +248,7 @@ impl<'a> Parser<'a> {
                     return Ok(Spanned {
                         node: Value::String(s, QuoteKind::Quoted),
                         span,
-                    })
+                    });
                 }
                 '\'' if q == '\'' => {
                     return Ok(Spanned {

src/parse/value/css_function.rs

@@ -47,6 +47,14 @@ impl<'a> Parser<'a> {
                         buf.push(')');
                     }
                 }
+                q @ '\'' | q @ '"' => {
+                    buf.push(q);
+                    match self.parse_quoted_string(q)?.node {
+                        Value::String(ref s, ..) => buf.push_str(s),
+                        _ => unreachable!(),
+                    }
+                    buf.push(q);
+                }
                 c => buf.push(c),
             }
         }

tests/special-functions.rs

@@ -49,6 +49,16 @@ test!(
     "a {\n  color: -webkit-calc(1 + 2);\n}\n",
     "a {\n  color: -webkit-calc(1 + 2);\n}\n"
 );
+test!(
+    calc_quoted_string,
+    r#"a { color: calc("\ "); }"#,
+    "a {\n  color: calc(\" \");\n}\n"
+);
+test!(
+    calc_quoted_string_single_quoted_paren,
+    "a {\n  color: calc(\")\");\n}\n",
+    "a {\n  color: calc(\")\");\n}\n"
+);
 test!(
     element_whitespace,
     "a {\n  color: element(       1      );\n}\n",