css combinator can be a single byte

Author: evanw

internal/css_ast/css_ast.go

@@ -468,7 +468,7 @@ func (r *RSelector) Hash() (uint32, bool) {
 			for _, sub := range sel.SubclassSelectors {
 				hash = helpers.HashCombine(hash, sub.Hash())
 			}
-			hash = helpers.HashCombineString(hash, sel.Combinator)
+			hash = helpers.HashCombine(hash, uint32(sel.Combinator))
 		}
 	}
 	hash = HashRules(hash, r.Rules)
@@ -629,10 +629,10 @@ func (a ComplexSelector) Equal(b ComplexSelector, check *CrossFileEqualityCheck)
 }
 
 type CompoundSelector struct {
-	Combinator         string // Optional, may be ""
 	TypeSelector       *NamespacedName
 	SubclassSelectors  []SS
-	HasNestingSelector bool // "&"
+	Combinator         uint8 // Optional, may be 0
+	HasNestingSelector bool  // "&"
 }
 
 type NameToken struct {

internal/css_parser/css_parser.go

@@ -611,7 +611,7 @@ func isSafeSelectors(complexSelectors []css_ast.ComplexSelector) bool {
 				return false
 			}
 
-			if compound.Combinator != "" {
+			if compound.Combinator != 0 {
 				// "Before Internet Explorer 10, the combinator only works in standards mode"
 				// Reference: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors
 				return false

internal/css_parser/css_parser_selector.go

@@ -51,7 +51,7 @@ func (p *parser) parseComplexSelector(opts parseSelectorOpts) (result css_ast.Co
 	// This is an extension: https://drafts.csswg.org/css-nesting-1/
 	r := p.current().Range
 	combinator := p.parseCombinator()
-	if combinator != "" {
+	if combinator != 0 {
 		if opts.isTopLevel {
 			p.maybeWarnAboutNesting(r)
 		}
@@ -74,7 +74,7 @@ func (p *parser) parseComplexSelector(opts parseSelectorOpts) (result css_ast.Co
 
 		// Optional combinator
 		combinator := p.parseCombinator()
-		if combinator != "" {
+		if combinator != 0 {
 			p.eat(css_lexer.TWhitespace)
 		}
 
@@ -366,21 +366,21 @@ loop:
 	return tokens
 }
 
-func (p *parser) parseCombinator() string {
+func (p *parser) parseCombinator() uint8 {
 	switch p.current().Kind {
 	case css_lexer.TDelimGreaterThan:
 		p.advance()
-		return ">"
+		return '>'
 
 	case css_lexer.TDelimPlus:
 		p.advance()
-		return "+"
+		return '+'
 
 	case css_lexer.TDelimTilde:
 		p.advance()
-		return "~"
+		return '~'
 
 	default:
-		return ""
+		return 0
 	}
 }

internal/css_printer/css_printer.go

@@ -351,18 +351,18 @@ func (p *printer) printComplexSelectors(selectors []css_ast.ComplexSelector, ind
 }
 
 func (p *printer) printCompoundSelector(sel css_ast.CompoundSelector, isFirst bool, isLast bool) {
-	if !isFirst && sel.Combinator == "" {
+	if !isFirst && sel.Combinator == 0 {
 		// A space is required in between compound selectors if there is no
 		// combinator in the middle. It's fine to convert "a + b" into "a+b"
 		// but not to convert "a b" into "ab".
 		p.print(" ")
 	}
 
-	if sel.Combinator != "" {
+	if sel.Combinator != 0 {
 		if !isFirst && !p.options.MinifyWhitespace {
 			p.print(" ")
 		}
-		p.print(sel.Combinator)
+		p.css = append(p.css, sel.Combinator)
 		if !p.options.MinifyWhitespace {
 			p.print(" ")
 		}