style(parser): cutprefix, default case, comma and tokens rename

parser/parser.go

@@ -30,8 +30,8 @@ func (e Error) Error() string {
 // Parse scans and parses src, returning the file and any diagnostics.  The
 // returned file is usable even when errors is non-empty.
 func Parse(path, src string) (*ast.File, []error) {
-	toks := lexer.Tokenize(src)
-	lines := splitLines(toks)
+	tokens := lexer.Tokenize(src)
+	lines := splitLines(tokens)
 	p := &state{path: path}
 	p.parse(lines)
 	return p.file, p.errs
@@ -52,10 +52,10 @@ func (p *state) errorf(pos token.Position, format string, args ...any) {
 }
 
 // splitLines groups the token stream into lines, dropping the Newline tokens.
-func splitLines(toks []token.Token) [][]token.Token {
+func splitLines(tokens []token.Token) [][]token.Token {
 	var lines [][]token.Token
 	var cur []token.Token
-	for _, t := range toks {
+	for _, t := range tokens {
 		if t.Kind == token.EOF {
 			break
 		}
@@ -403,7 +403,7 @@ func parseAddress(g []token.Token) ast.Address {
 	}
 	// Symbol-with-pseudo form: name[<>][+off](PSEUDO).
 	// When the prefix is not a valid symbol name (e.g. a bare number like
-	// 0(SP) in RISC-V), sym is nil and we fall through to regular memory
+	// 0(SP) in RISC-V), sym is nil, and we fall through to regular memory
 	// operand parsing instead of returning an empty address.
 	if idx := findPseudoParen(g); idx >= 0 {
 		sym, _ := parseSymbolPrefix(g[:idx+3])
@@ -549,6 +549,9 @@ func splitFirstComma(g []token.Token) (before, after []token.Token) {
 			if depth == 0 {
 				return g[:i], g[i+1:]
 			}
+		default:
+			// Every other token kind is inert at the top level of the
+			// group; the scan just keeps looking for the first comma.
 		}
 	}
 	return g, nil
@@ -615,13 +618,12 @@ func joinRaw(g []token.Token) string {
 
 // commentText removes a leading // or /* marker from a comment token's text.
 func commentText(s string) string {
-	if strings.HasPrefix(s, "//") {
-		return strings.TrimSpace(strings.TrimPrefix(s, "//"))
+	if body, ok := strings.CutPrefix(s, "//"); ok {
+		return strings.TrimSpace(body)
 	}
-	if strings.HasPrefix(s, "/*") {
-		s = strings.TrimPrefix(s, "/*")
-		s = strings.TrimSuffix(s, "*/")
-		return strings.TrimSpace(s)
+	if body, ok := strings.CutPrefix(s, "/*"); ok {
+		body = strings.TrimSuffix(body, "*/")
+		return strings.TrimSpace(body)
 	}
 	return s
 }