checker: produce more informative error messages on ~,!,-,<- operator…

… type mismatches

vlib/v/checker/checker.v

@@ -3415,42 +3415,48 @@ pub fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) ast.Type {
 			return right_type.ref()
 		}
 	}
+	right_sym := c.table.final_sym(c.unwrap_generic(right_type))
 	if node.op == .mul {
 		if right_type.is_ptr() {
 			return right_type.deref()
 		}
 		if !right_type.is_pointer() && !c.pref.translated && !c.file.is_translated {
 			s := c.table.type_to_str(right_type)
-			c.error('invalid indirect of `$s`', node.pos)
+			c.error('invalid indirect of `$s`, the type `$right_sym.name` is not a pointer',
+				node.pos)
 		}
 		if right_type.is_voidptr() {
 			c.error('cannot dereference to void', node.pos)
 		}
 	}
 	if node.op == .bit_not && !right_type.is_int() && !c.pref.translated && !c.file.is_translated {
-		c.error('operator ~ only defined on int types', node.pos)
+		c.type_error_for_operator('~', 'integer', right_sym.name, node.pos)
 	}
 	if node.op == .not && right_type != ast.bool_type_idx && !c.pref.translated
 		&& !c.file.is_translated {
-		c.error('! operator can only be used with bool types', node.pos)
+		c.type_error_for_operator('!', 'bool', right_sym.name, node.pos)
 	}
 	// FIXME
 	// there are currently other issues to investigate if right_type
 	// is unwraped directly as initialization, so do it here
-	right_sym := c.table.final_sym(c.unwrap_generic(right_type))
 	if node.op == .minus && !right_sym.is_number() {
-		c.error('- operator can only be used with numeric types', node.pos)
+		c.type_error_for_operator('-', 'numeric', right_sym.name, node.pos)
 	}
 	if node.op == .arrow {
 		if right_sym.kind == .chan {
 			c.stmts_ending_with_expression(node.or_block.stmts)
 			return right_sym.chan_info().elem_type
 		}
-		c.error('<- operator can only be used with `chan` types', node.pos)
+		c.type_error_for_operator('<-', '`chan`', right_sym.name, node.pos)
 	}
 	return right_type
 }
 
+fn (mut c Checker) type_error_for_operator(op_label string, types_label string, found_type_label string, pos token.Pos) {
+	c.error('operator `$op_label` can only be used with $types_label types, but the value after `$op_label` is of type `$found_type_label` instead',
+		pos)
+}
+
 fn (mut c Checker) check_index(typ_sym &ast.TypeSymbol, index ast.Expr, index_type ast.Type, pos token.Pos, range_index bool, is_gated bool) {
 	index_type_sym := c.table.sym(index_type)
 	if typ_sym.kind in [.array, .array_fixed, .string] {

vlib/v/checker/tests/arrow_op_wrong_right_type_err_b.out

@@ -1,4 +1,4 @@
-vlib/v/checker/tests/arrow_op_wrong_right_type_err_b.vv:3:9: error: <- operator can only be used with `chan` types
+vlib/v/checker/tests/arrow_op_wrong_right_type_err_b.vv:3:9: error: operator `<-` can only be used with `chan` types, but the value after `<-` is of type `i64` instead
     1 | fn main() {
     2 |     ch := i64(3)
     3 |     obj := <-ch

vlib/v/checker/tests/invert_other_types_bits_error.out

@@ -1,26 +1,26 @@
-vlib/v/checker/tests/invert_other_types_bits_error.vv:2:13: error: operator ~ only defined on int types
-    1 | fn main() {
-    2 |     println(~3.0)
-      |             ^
-    3 |     println(~10.5)
-    4 |     println(~'2')
-vlib/v/checker/tests/invert_other_types_bits_error.vv:3:13: error: operator ~ only defined on int types
-    1 | fn main() {
-    2 |     println(~3.0)
-    3 |     println(~10.5)
-      |             ^
-    4 |     println(~'2')
-    5 |     println(~[2, 4, 6])
-vlib/v/checker/tests/invert_other_types_bits_error.vv:4:13: error: operator ~ only defined on int types
-    2 |     println(~3.0)
-    3 |     println(~10.5)
-    4 |     println(~'2')
-      |             ^
-    5 |     println(~[2, 4, 6])
-    6 | }
-vlib/v/checker/tests/invert_other_types_bits_error.vv:5:13: error: operator ~ only defined on int types
-    3 |     println(~10.5)
-    4 |     println(~'2')
-    5 |     println(~[2, 4, 6])
-      |             ^
-    6 | }
+vlib/v/checker/tests/invert_other_types_bits_error.vv:2:13: error: operator `~` can only be used with integer types, but the value after `~` is of type `float literal` instead
+    1 | fn main() {
+    2 |     println(~3.0)
+      |             ^
+    3 |     println(~10.5)
+    4 |     println(~'2')
+vlib/v/checker/tests/invert_other_types_bits_error.vv:3:13: error: operator `~` can only be used with integer types, but the value after `~` is of type `float literal` instead
+    1 | fn main() {
+    2 |     println(~3.0)
+    3 |     println(~10.5)
+      |             ^
+    4 |     println(~'2')
+    5 |     println(~[2, 4, 6])
+vlib/v/checker/tests/invert_other_types_bits_error.vv:4:13: error: operator `~` can only be used with integer types, but the value after `~` is of type `string` instead
+    2 |     println(~3.0)
+    3 |     println(~10.5)
+    4 |     println(~'2')
+      |             ^
+    5 |     println(~[2, 4, 6])
+    6 | }
+vlib/v/checker/tests/invert_other_types_bits_error.vv:5:13: error: operator `~` can only be used with integer types, but the value after `~` is of type `[]int` instead
+    3 |     println(~10.5)
+    4 |     println(~'2')
+    5 |     println(~[2, 4, 6])
+      |             ^
+    6 | }

vlib/v/checker/tests/minus_op_wrong_type_err.out

@@ -40,21 +40,21 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:16:10: error: mismatched types `
       |             ~~~~~~
    17 |     println(-Aaa{})
    18 |     println(-a)
-vlib/v/checker/tests/minus_op_wrong_type_err.vv:17:10: error: - operator can only be used with numeric types
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:17:10: error: operator `-` can only be used with numeric types, but the value after `-` is of type `Aaa` instead
    15 |     println(a - 10)
    16 |     println(10 - a)
    17 |     println(-Aaa{})
       |             ^
    18 |     println(-a)
    19 |     println(-Color.red)
-vlib/v/checker/tests/minus_op_wrong_type_err.vv:18:10: error: - operator can only be used with numeric types
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:18:10: error: operator `-` can only be used with numeric types, but the value after `-` is of type `map[string]int` instead
    16 |     println(10 - a)
    17 |     println(-Aaa{})
    18 |     println(-a)
       |             ^
    19 |     println(-Color.red)
    20 | }
-vlib/v/checker/tests/minus_op_wrong_type_err.vv:19:10: error: - operator can only be used with numeric types
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:19:10: error: operator `-` can only be used with numeric types, but the value after `-` is of type `Color` instead
    17 |     println(-Aaa{})
    18 |     println(-a)
    19 |     println(-Color.red)

vlib/v/checker/tests/prefix_err.out

@@ -68,7 +68,7 @@ vlib/v/checker/tests/prefix_err.vv:14:6: error: cannot take the address of 1 + 2
       |      ^
    15 | _ := 12.3
    16 |
-vlib/v/checker/tests/prefix_err.vv:18:5: error: invalid indirect of `int`
+vlib/v/checker/tests/prefix_err.vv:18:5: error: invalid indirect of `int`, the type `int` is not a pointer
    16 | 
    17 | a := 1
    18 | _ = *a
@@ -82,13 +82,13 @@ vlib/v/checker/tests/prefix_err.vv:19:1: error: cannot push on non-channel `int`
       | ^
    20 | 
    21 | _ = ~true
-vlib/v/checker/tests/prefix_err.vv:21:5: error: operator ~ only defined on int types
+vlib/v/checker/tests/prefix_err.vv:21:5: error: operator `~` can only be used with integer types, but the value after `~` is of type `bool` instead
    19 | a <- 4
    20 | 
    21 | _ = ~true
       |     ^
    22 | _ = !4
-vlib/v/checker/tests/prefix_err.vv:22:5: error: ! operator can only be used with bool types
+vlib/v/checker/tests/prefix_err.vv:22:5: error: operator `!` can only be used with bool types, but the value after `!` is of type `int literal` instead
    20 | 
    21 | _ = ~true
    22 | _ = !4