// A common syntax error is to write '=' instead of '==',
// which turns an expression into an assignment. Provide
// a more explicit error message in that case to prevent
// further confusion.
var str string
if as, ok := s.(*AssignStmt); ok && as.Op == 0 {
	// Emphasize Lhs and Rhs of assignment with parentheses to highlight '='.
	// Do it always - it's not worth going through the trouble of doing it
	// only for "complex" left and right sides.
	str = "assignment (" + String(as.Lhs) + ") = (" + String(as.Rhs) + ")"
} else {
	str = String(s)
}

package p

func _(x, y int) {
	if x = y {}
}