checker: add more checks for modulo

vlib/v/checker/checker.v

@@ -448,12 +448,16 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 				c.error('mismatched types `$left.name` and `$right.name`', infix_expr.right.position())
 			} else if !left.is_int() && right.is_int() {
 				c.error('mismatched types `$left.name` and `$right.name`', infix_expr.left.position())
+			} else if left.kind == .f32 && right.kind == .f32 || left.kind == .f64 && right.kind == .f64 {
+				c.error('float modulo not allowed, use math.fmod() instead', infix_expr.left.position())
 			} else if left.kind in [.f32, .f64, .string, .array, .array_fixed, .map, .struct_] &&
 				!left.has_method(infix_expr.op.str()) {
 				c.error('mismatched types `$left.name` and `$right.name`', infix_expr.left.position())
 			} else if right.kind in [.f32, .f64, .string, .array, .array_fixed, .map, .struct_] &&
 				!right.has_method(infix_expr.op.str()) {
 				c.error('mismatched types `$left.name` and `$right.name`', infix_expr.right.position())
+			} else if infix_expr.right is ast.IntegerLiteral && infix_expr.right.str() == '0' {
+				c.error('modulo by zero', infix_expr.right.position())
 			}
 		}
 		else {}

vlib/v/checker/tests/float_modulo_err.out

@@ -0,0 +1,12 @@
+vlib/v/checker/tests/float_modulo_err.v:2:13: error: float modulo not allowed, use math.fmod() instead 
+    1 | fn main() {
+    2 |     println(3.0 % 2.0)
+      |             ~~~
+    3 |     println(f32(3.0) % f32(2.0))
+    4 | }
+vlib/v/checker/tests/float_modulo_err.v:3:17: error: float modulo not allowed, use math.fmod() instead
+    1 | fn main() {
+    2 |     println(3.0 % 2.0)
+    3 |     println(f32(3.0) % f32(2.0))
+      |                 ~~~
+    4 | }

vlib/v/checker/tests/float_modulo_err.vv

@@ -0,0 +1,4 @@
+fn main() {
+    println(3.0 % 2.0)
+    println(f32(3.0) % f32(2.0))
+}

vlib/v/checker/tests/int_modulo_by_zero_err.out

@@ -0,0 +1,5 @@
+vlib/v/checker/tests/int_modulo_by_zero_err.v:2:17: error: modulo by zero 
+    1 | fn main() {
+    2 |     println(3 % 0)
+      |                 ^
+    3 | }

vlib/v/checker/tests/int_modulo_by_zero_err.vv

@@ -0,0 +1,3 @@
+fn main() {
+    println(3 % 0)
+}