builtin,gen: use operator overloading on ustring (#10197)

vlib/builtin/string.v

@@ -1300,41 +1300,15 @@ pub fn (s string) ustring_tmp() ustring {
 	return res
 }
 
-// eq implements the `u == a` (equal) operator.
-fn (u ustring) eq(a ustring) bool {
-	if u.len != a.len || u.s != a.s {
-		return false
-	}
-	return true
+fn (u ustring) == (a ustring) bool {
+	return u.s == a.s
 }
 
-// ne implements the `u != a` (not equal) operator.
-fn (u ustring) ne(a ustring) bool {
-	return !u.eq(a)
-}
-
-// lt implements the `u < a` (less than) operator.
-fn (u ustring) lt(a ustring) bool {
+fn (u ustring) < (a ustring) bool {
 	return u.s < a.s
 }
 
-// le implements the `u <= a` (less than or equal to) operator.
-fn (u ustring) le(a ustring) bool {
-	return u.lt(a) || u.eq(a)
-}
-
-// gt implements the `u > a` (greater than) operator.
-fn (u ustring) gt(a ustring) bool {
-	return !u.le(a)
-}
-
-// ge implements the `u >= a` (greater than or equal to) operator.
-fn (u ustring) ge(a ustring) bool {
-	return !u.lt(a)
-}
-
-// add concatenates ustring with the string given in `s`.
-pub fn (u ustring) add(a ustring) ustring {
+fn (u ustring) + (a ustring) ustring {
 	mut res := ustring{
 		s: u.s + a.s
 		runes: __new_array(0, u.s.len + a.s.len, int(sizeof(int)))

vlib/readline/readline_linux.c.v

@@ -401,10 +401,11 @@ fn (mut r Readline) eof() bool {
 // insert_character inserts the character `c` at current cursor position.
 fn (mut r Readline) insert_character(c int) {
 	if !r.overwrite || r.cursor == r.current.len {
-		r.current = r.current.left(r.cursor).ustring().add(utf32_to_str(u32(c)).ustring()).add(r.current.right(r.cursor).ustring())
+		r.current = r.current.left(r.cursor).ustring() + utf32_to_str(u32(c)).ustring() +
+			r.current.right(r.cursor).ustring()
 	} else {
-		r.current = r.current.left(r.cursor).ustring().add(utf32_to_str(u32(c)).ustring()).add(r.current.right(
-			r.cursor + 1).ustring())
+		r.current = r.current.left(r.cursor).ustring() + utf32_to_str(u32(c)).ustring() +
+			r.current.right(r.cursor + 1).ustring()
 	}
 	r.cursor++
 	// Refresh the line to add the new character
@@ -419,7 +420,7 @@ fn (mut r Readline) delete_character() {
 		return
 	}
 	r.cursor--
-	r.current = r.current.left(r.cursor).ustring().add(r.current.right(r.cursor + 1).ustring())
+	r.current = r.current.left(r.cursor).ustring() + r.current.right(r.cursor + 1).ustring()
 	r.refresh_line()
 }
 
@@ -428,7 +429,7 @@ fn (mut r Readline) suppr_character() {
 	if r.cursor > r.current.len {
 		return
 	}
-	r.current = r.current.left(r.cursor).ustring().add(r.current.right(r.cursor + 1).ustring())
+	r.current = r.current.left(r.cursor).ustring() + r.current.right(r.cursor + 1).ustring()
 	r.refresh_line()
 }
 
@@ -436,7 +437,7 @@ fn (mut r Readline) suppr_character() {
 fn (mut r Readline) commit_line() bool {
 	r.previous_lines.insert(1, r.current)
 	a := '\n'.ustring()
-	r.current = r.current.add(a)
+	r.current += a
 	r.cursor = r.current.len
 	if r.is_tty {
 		r.refresh_line()

vlib/v/gen/c/cgen.v

@@ -3702,41 +3702,8 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 	} else {
 		node.right_type
 	}
-	if unaliased_left == ast.ustring_type_idx {
-		fn_name := match node.op {
-			.plus {
-				'ustring_add('
-			}
-			.eq {
-				'ustring_eq('
-			}
-			.ne {
-				'ustring_ne('
-			}
-			.lt {
-				'ustring_lt('
-			}
-			.le {
-				'ustring_le('
-			}
-			.gt {
-				'ustring_gt('
-			}
-			.ge {
-				'ustring_ge('
-			}
-			else {
-				verror('op error for type `$left_sym.name`')
-				'/*node error*/'
-			}
-		}
-		g.write(fn_name)
-		g.expr(node.left)
-		g.write(', ')
-		g.expr(node.right)
-		g.write(')')
-	} else if unaliased_left == ast.string_type_idx && op_is_eq_or_ne
-		&& node.right is ast.StringLiteral && (node.right as ast.StringLiteral).val == '' {
+	if unaliased_left == ast.string_type_idx && op_is_eq_or_ne && node.right is ast.StringLiteral
+		&& (node.right as ast.StringLiteral).val == '' {
 		// `str == ''` -> `str.len == 0` optimization
 		g.write('(')
 		g.expr(node.left)
@@ -3845,6 +3812,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 		is_v_struct := ((left_sym.name[0].is_capital() || left_sym.name.contains('.'))
 			&& left_sym.kind !in [.enum_, .function, .interface_, .sum_type]
 			&& left_sym.language != .c) || left_sym.kind == .string
+			|| unaliased_left == ast.ustring_type
 		is_alias := left_sym.kind == .alias
 		is_c_alias := is_alias && (left_sym.info as ast.Alias).language == .c
 		// Check if aliased type is a struct