all: only allow defining `==` and `<` and auto generate `!=`, `>`, `>=` and `<=` (#8520)

CHANGELOG.md

@@ -27,6 +27,7 @@ from local variables.
 - `__offsetof` for low level needs (works like `offsetof` in C).
 - vfmt now preserves empty lines, like gofmt.
 - Support for compile time environment variables via `$env('ENV_VAR')`.
+- Allow method declaration of `==` and `<` operators and auto generate `!=`, `>`, `<=` and `>=`.
 
 ## V 0.2.1
 *30 Dec 2020*

doc/docs.md

@@ -3637,7 +3637,8 @@ To improve safety and maintainability, operator overloading is limited:
 - `==` and `!=` are self generated by the compiler but can be overriden.
 - Calling other functions inside operator functions is not allowed.
 - Operator functions can't modify their arguments.
-- When using `<`, `>`, `>=`, `<=`, `==` and `!=` operators, the return type must be `bool`.
+- When using `<` and `==` operators, the return type must be `bool`.
+- `!=`, `>`, `<=` and `>=` are auto generated when `==` and `<` are defined.
 - Both arguments must have the same type (just like with all operators in V).
 - Assignment operators (`*=`, `+=`, `/=`, etc)
 are auto generated when the operators are defined though they must return the same type.

vlib/time/operator.v

@@ -9,12 +9,6 @@ pub fn (t1 Time) == (t2 Time) bool {
 	return false
 }
 
-// operator `!=` returns true if provided time is not equal to time
-[inline]
-pub fn (t1 Time) != (t2 Time) bool {
-	return !(t1 == t2)
-}
-
 // operator `<` returns true if provided time is less than time
 [inline]
 pub fn (t1 Time) < (t2 Time) bool {
@@ -24,27 +18,6 @@ pub fn (t1 Time) < (t2 Time) bool {
 	return false
 }
 
-// operator `<=` returns true if provided time is less or equal to time
-[inline]
-pub fn (t1 Time) <= (t2 Time) bool {
-	return t1 < t2 || t1 == t2
-}
-
-// operator `>` returns true if provided time is greater than time
-[inline]
-pub fn (t1 Time) > (t2 Time) bool {
-	if t1.unix > t2.unix || (t1.unix == t2.unix && t1.microsecond > t2.microsecond) {
-		return true
-	}
-	return false
-}
-
-// operator `>=` returns true if provided time is greater or equal to time
-[inline]
-pub fn (t1 Time) >= (t2 Time) bool {
-	return t1 > t2 || t1 == t2
-}
-
 // Time subtract using operator overloading.
 [inline]
 pub fn (lhs Time) - (rhs Time) Duration {

vlib/v/checker/checker.v

@@ -882,7 +882,7 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 		.gt, .lt, .ge, .le {
 			if left.kind in [.array, .array_fixed] && right.kind in [.array, .array_fixed] {
 				c.error('only `==` and `!=` are defined on arrays', infix_expr.pos)
-			} else if left.kind == .struct_ && right.kind == .struct_ {
+			} else if left.kind == .struct_ && right.kind == .struct_ && infix_expr.op in [.eq, .lt] {
 				if !(left.has_method(infix_expr.op.str()) && right.has_method(infix_expr.op.str())) {
 					left_name := c.table.type_to_str(left_type)
 					right_name := c.table.type_to_str(right_type)
@@ -894,6 +894,14 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 					}
 				}
 			}
+			if left.kind == .struct_ && right.kind == .struct_ {
+				if !left.has_method('<') && infix_expr.op in [.ge, .le] {
+					c.error('cannot use `$infix_expr.op` as `<` operator method is not defined',
+						infix_expr.pos)
+				} else if !left.has_method('<') && infix_expr.op == .gt {
+					c.error('cannot use `>` as `<=` operator method is not defined', infix_expr.pos)
+				}
+			}
 		}
 		.left_shift {
 			if left.kind == .array {
@@ -5617,8 +5625,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 			c.error('.str() methods should have 0 arguments', node.pos)
 		}
 	}
-	if node.language == .v && node.is_method
+	if node.language == .v && node.is_method && node.name in ['+', '-', '*', '%', '/', '<', '=='] {
-		&& node.name in ['+', '-', '*', '%', '/', '<', '>', '==', '!=', '>=', '<='] {
 		if node.params.len != 2 {
 			c.error('operator methods should have exactly 1 argument', node.pos)
 		} else {
@@ -5636,8 +5643,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 				} else if node.receiver.typ != node.params[1].typ {
 					c.error('expected `$receiver_sym.name` not `$param_sym.name` - both operands must be the same type for operator overloading',
 						node.params[1].type_pos)
-				} else if node.name in ['<', '>', '==', '!=', '>=', '<=']
+				} else if node.name in ['<', '=='] && node.return_type != table.bool_type {
-					&& node.return_type != table.bool_type {
 					c.error('operator comparison methods should return `bool`', node.pos)
 				} else if parent_sym.is_primitive() {
 					c.error('cannot define operator methods on type alias for `$parent_sym.name`',

vlib/v/checker/tests/method_op_err.out

@@ -12,65 +12,58 @@ vlib/v/checker/tests/method_op_err.vv:14:18: error: expected `User` not `Foo` -
       |                  ~~~
    15 |     return User{u.a - f.a, u.b-f.a}
    16 | }
-vlib/v/checker/tests/method_op_err.vv:18:1: error: operator comparison methods should return `bool`
+vlib/v/checker/tests/method_op_err.vv:18:9: error: receiver cannot be `mut` for operator overloading
    16 | }
    17 | 
-   18 | fn (u User) > (u1 User) User {
+   18 | fn (mut u User) * (u1 User) User {
-      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+      |         ~~~~~~
    19 |     return User{}
    20 | }
-vlib/v/checker/tests/method_op_err.vv:22:9: error: receiver cannot be `mut` for operator overloading
+vlib/v/checker/tests/method_op_err.vv:22:1: error: argument cannot be `mut` for operator overloading
    20 | }
    21 | 
-   22 | fn (mut u User) * (u1 User) User {
+   22 | fn (u User) / (mut u1 User) User {
-      |         ~~~~~~
+      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    23 |     return User{}
    24 | }
-vlib/v/checker/tests/method_op_err.vv:26:1: error: argument cannot be `mut` for operator overloading
+vlib/v/checker/tests/method_op_err.vv:32:24: error: infix expr: cannot use `Foo` (right expression) as `User`
-   24 | }
+   30 | fn main() {
-   25 | 
+   31 |     println(User{3, 4})
-   26 | fn (u User) / (mut u1 User) User {
+   32 |     println(User{3, 4} - Foo{3, 3})
-      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-   27 |     return User{}
-   28 | }
-vlib/v/checker/tests/method_op_err.vv:36:24: error: infix expr: cannot use `Foo` (right expression) as `User`
-   34 | fn main() {
-   35 |     println(User{3, 4})
-   36 |     println(User{3, 4} - Foo{3, 3})
       |                        ^
-   37 |     println(User{3, 2} < User{2, 4})
+   33 |     println(User{3, 2} < User{2, 4})
-   38 |     println(User{3, 4} < Foo{3, 4})
+   34 |     println(User{3, 4} < Foo{3, 4})
-vlib/v/checker/tests/method_op_err.vv:37:24: error: undefined operation `User` < `User`
+vlib/v/checker/tests/method_op_err.vv:33:24: error: undefined operation `User` < `User`
-   35 |     println(User{3, 4})
+   31 |     println(User{3, 4})
-   36 |     println(User{3, 4} - Foo{3, 3})
+   32 |     println(User{3, 4} - Foo{3, 3})
-   37 |     println(User{3, 2} < User{2, 4})
+   33 |     println(User{3, 2} < User{2, 4})
       |                        ^
-   38 |     println(User{3, 4} < Foo{3, 4})
+   34 |     println(User{3, 4} < Foo{3, 4})
-   39 |     mut u := User{3, 4}
+   35 |     mut u := User{3, 4}
-vlib/v/checker/tests/method_op_err.vv:38:24: error: mismatched types `User` and `Foo`
+vlib/v/checker/tests/method_op_err.vv:34:24: error: mismatched types `User` and `Foo`
-   36 |     println(User{3, 4} - Foo{3, 3})
+   32 |     println(User{3, 4} - Foo{3, 3})
-   37 |     println(User{3, 2} < User{2, 4})
+   33 |     println(User{3, 2} < User{2, 4})
-   38 |     println(User{3, 4} < Foo{3, 4})
+   34 |     println(User{3, 4} < Foo{3, 4})
       |                        ^
-   39 |     mut u := User{3, 4}
+   35 |     mut u := User{3, 4}
-   40 |     u += 12
+   36 |     u += 12
-vlib/v/checker/tests/method_op_err.vv:40:10: error: cannot assign to `u`: expected `User`, not `int literal`
+vlib/v/checker/tests/method_op_err.vv:36:10: error: cannot assign to `u`: expected `User`, not `int literal`
-   38 |     println(User{3, 4} < Foo{3, 4})
+   34 |     println(User{3, 4} < Foo{3, 4})
-   39 |     mut u := User{3, 4}
+   35 |     mut u := User{3, 4}
-   40 |     u += 12
+   36 |     u += 12
       |          ~~
-   41 |     u %= User{1, 3}
+   37 |     u %= User{1, 3}
-   42 |     u += User{2, 3}
+   38 |     u += User{2, 3}
-vlib/v/checker/tests/method_op_err.vv:41:5: error: operator %= not defined on left operand type `User`
+vlib/v/checker/tests/method_op_err.vv:37:5: error: operator %= not defined on left operand type `User`
-   39 |     mut u := User{3, 4}
+   35 |     mut u := User{3, 4}
-   40 |     u += 12
+   36 |     u += 12
-   41 |     u %= User{1, 3}
+   37 |     u %= User{1, 3}
       |     ^
-   42 |     u += User{2, 3} 
+   38 |     u += User{2, 3} 
-   43 | }
+   39 | }
-vlib/v/checker/tests/method_op_err.vv:42:7: error: operator `+` must return `User` to be used as an assignment operator
+vlib/v/checker/tests/method_op_err.vv:38:7: error: operator `+` must return `User` to be used as an assignment operator
-   40 |     u += 12
+   36 |     u += 12
-   41 |     u %= User{1, 3}
+   37 |     u %= User{1, 3}
-   42 |     u += User{2, 3} 
+   38 |     u += User{2, 3} 
       |       ~~
-   43 | }
+   39 | }

vlib/v/checker/tests/method_op_err.vv

@@ -15,10 +15,6 @@ fn (u User) - (f Foo) User {
     return User{u.a - f.a, u.b-f.a}
 }
 
-fn (u User) > (u1 User) User {
-    return User{}
-}
-
 fn (mut u User) * (u1 User) User {
     return User{}
 }

vlib/v/gen/c/array.v

@@ -251,8 +251,8 @@ fn (mut g Gen) gen_array_sort(node ast.CallExpr) {
 		sym := g.table.get_type_symbol(typ)
 		if !is_reverse && sym.has_method('<') && infix_expr.left.str().len == 1 {
 			g.definitions.writeln('\tif (${styp}__lt(*a, *b)) { return -1; } else { return 1; }}')
-		} else if is_reverse && sym.has_method('>') && infix_expr.left.str().len == 1 {
+		} else if is_reverse && sym.has_method('<') && infix_expr.left.str().len == 1 {
-			g.definitions.writeln('\tif (${styp}__gt(*a, *b)) { return -1; } else { return 1; }}')
+			g.definitions.writeln('\tif (!${styp}__lt(*a, *b)) { return -1; } else { return 1; }}')
 		} else {
 			field_type := g.typ(infix_expr.left_type)
 			mut left_expr_str := g.write_expr_to_string(infix_expr.left)

vlib/v/gen/c/cgen.v

@@ -3019,7 +3019,6 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 	}
 	right_sym := g.table.get_type_symbol(node.right_type)
 	has_eq_overloaded := !left_sym.has_method('==')
-	has_ne_overloaded := !left_sym.has_method('!=')
 	unaliased_right := if right_sym.info is table.Alias {
 		right_sym.info.parent_type
 	} else {
@@ -3174,16 +3173,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 		g.expr(node.right)
 		g.write(')')
 	} else if node.op in [.eq, .ne] && left_sym.kind == .struct_ && right_sym.kind == .struct_ {
-		if has_eq_overloaded && !has_ne_overloaded {
+		if !has_eq_overloaded {
-			// Define `!=` as negation of Autogenerated `==`
-			styp := g.typ(left_type)
-			if node.op == .eq {
-				g.write('!${styp}__ne(')
-			} else if node.op == .ne {
-				g.write('${styp}__ne(')
-			}
-		}
-		if !has_eq_overloaded && has_ne_overloaded {
 			// Define `==` as negation of Autogenerated `!=`
 			styp := g.typ(left_type)
 			if node.op == .ne {
@@ -3192,16 +3182,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 				g.write('${styp}__eq(')
 			}
 		}
-		if !has_eq_overloaded && !has_ne_overloaded {
+		if has_eq_overloaded {
-			// Overload both User defined `==` and `!=`
-			styp := g.typ(left_type)
-			if node.op == .eq {
-				g.write('${styp}__eq(')
-			} else if node.op == .ne {
-				g.write('${styp}__ne(')
-			}
-		}
-		if has_eq_overloaded && has_ne_overloaded {
 			// Auto generate both `==` and `!=`
 			ptr_typ := g.gen_struct_equality_fn(left_type)
 			if node.op == .eq {
@@ -3374,8 +3355,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 			&& g.typ((left_sym.info as table.Alias).parent_type).split('__').last()[0].is_capital()
 		// Do not generate operator overloading with these `right_sym.kind`.
 		e := right_sym.kind !in [.voidptr, .int_literal, .int]
-		if node.op in [.plus, .minus, .mul, .div, .mod, .lt, .gt, .eq, .ne, .le, .ge]
+		if node.op in [.plus, .minus, .mul, .div, .mod, .lt, .eq] && ((a && b && e) || c || d) {
-			&& ((a && b && e) || c|| d) {
 			// Overloaded operators
 			g.write(g.typ(if !d { left_type } else { (left_sym.info as table.Alias).parent_type }))
 			g.write('_')
@@ -3385,6 +3365,28 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 			g.write(', ')
 			g.expr(node.right)
 			g.write(')')
+		} else if node.op in [.ne, .gt, .ge, .le] && ((a && b && e) || c || d) {
+			typ := g.typ(if !d { left_type } else { (left_sym.info as table.Alias).parent_type })
+			g.write('!$typ')
+			g.write('_')
+			if node.op == .ne {
+				g.write('_eq')
+			} else if node.op in [.ge, .le, .gt] {
+				g.write('_lt')
+			}
+			if node.op == .le {
+				g.write('(')
+				g.expr(node.right)
+				g.write(', ')
+				g.expr(node.left)
+				g.write(')')
+			} else {
+				g.write('(')
+				g.expr(node.left)
+				g.write(', ')
+				g.expr(node.right)
+				g.write(')')
+			}
 		} else {
 			need_par := node.op in [.amp, .pipe, .xor] // `x & y == 0` => `(x & y) == 0` in C
 			if need_par {

vlib/v/gen/c/fn.v

@@ -56,7 +56,7 @@ fn (mut g Gen) gen_fn_decl(node ast.FnDecl, skip bool) {
 	}
 	//
 	mut name := node.name
-	if name in ['+', '-', '*', '/', '%', '<', '>', '==', '!=', '<=', '>='] {
+	if name in ['+', '-', '*', '/', '%', '<', '=='] {
 		name = util.replace_op(name)
 	}
 	if node.is_method {

vlib/v/parser/fn.v

@@ -275,14 +275,16 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			}
 		}
 	}
-	if p.tok.kind in [.plus, .minus, .mul, .div, .mod, .gt, .lt, .eq, .ne, .le, .ge]
+	if p.tok.kind in [.plus, .minus, .mul, .div, .mod, .lt, .eq] && p.peek_tok.kind == .lpar {
-		&& p.peek_tok.kind == .lpar {
 		name = p.tok.kind.str() // op_to_fn_name()
 		if rec_type == table.void_type {
 			p.error_with_pos('cannot use operator overloading with normal functions',
 				p.tok.position())
 		}
 		p.next()
+	} else if p.tok.kind in [.ne, .gt, .ge, .le] && p.peek_tok.kind == .lpar {
+		p.error_with_pos('cannot overload `!=`, `>`, `<=` and `>=` as they are auto generated with `==` and`<`',
+			p.tok.position())
 	}
 	// <T>
 	generic_params := p.parse_generic_params()

vlib/v/tests/operator_overloading_with_string_interpolation_test.v

@@ -27,10 +27,6 @@ fn (a Vec) % (b Vec) Vec {
 	return Vec{a.x % b.x, a.y % b.y}
 }
 
-fn (a Vec) > (b Vec) bool {
-	return a.x > b.x && a.y > b.y
-}
-
 fn (a Vec) < (b Vec) bool {
 	return a.x < b.x && a.y < b.y
 }
@@ -39,18 +35,6 @@ fn (a Vec) == (b Vec) bool {
 	return a.x == b.y && a.y == b.x
 }
 
-fn (a Vec) != (b Vec) bool {
-	return !(a == b)
-}
-
-fn (a Vec) >= (b Vec) bool {
-	return a > b || a == b
-}
-
-fn (a Vec) <= (b Vec) bool {
-	return a < b || a == b
-}
-
 fn test_operator_overloading_with_string_interpolation() {
 	a := Vec{2, 3}
 	b := Vec{4, 5}

vlib/v/tests/sorting_by_different_criteria_test.v

@@ -11,10 +11,6 @@ fn (p Parent) < (p1 Parent) bool {
     return p.name < p1.name
 }
 
-fn (p Parent) > (p1 Parent) bool {
-    return p.name > p1.name
-}
-
 fn test_sorting_by_different_criteria_in_same_function() {
 	mut arr := [
 		Parent{Child{0.2}, 'def'},

vlib/v/tests/sturct_ne_op_only_test.v

@@ -1,15 +0,0 @@
-struct User {
-	name string
-	num int
-}
-
-fn (u User) != (u1 User) bool {
-	return u.num != u1.num
-}
-
-fn test_eq_op() {
-	u1 := User{'Joe', 23}
-	u2 := User{'Joe', 24}
-	assert u1 != u2
-	assert (u1 == u2) == false
-}

vlib/v/util/util.v

@@ -382,9 +382,6 @@ pub fn replace_op(s string) string {
 	} else {
 		suffix := match s {
 			'==' { '_eq' }
-			'!=' { '_ne' }
-			'<=' { '_le' }
-			'>=' { '_ge' }
 			else { '' }
 		}
 		return s[..s.len - 2] + suffix