checker: add a suggestion for misspelled mod.const_name + a test

vlib/v/checker/checker.v

@@ -3395,10 +3395,24 @@ pub fn (mut c Checker) ident(mut node ast.Ident) ast.Type {
 		if c.inside_ct_attr {
 			c.note('`[if $node.name]` is deprecated. Use `[if $node.name?]` instead',
 				node.pos)
+		} else {
+			cname_mod := node.name.all_before('.')
+			if cname_mod.len != node.name.len {
+				mut const_names_in_mod := []string{}
+				for _, so in c.table.global_scope.objects {
+					if so is ast.ConstField {
+						if so.mod == cname_mod {
+							const_names_in_mod << so.name
+						}
+					}
+				}
+				c.error(util.new_suggestion(node.name, const_names_in_mod).say('undefined ident: `$node.name`'),
+					node.pos)
 			} else {
 				c.error('undefined ident: `$node.name`', node.pos)
 			}
 		}
+	}
 	if c.table.known_type(node.name) {
 		// e.g. `User`  in `json.decode(User, '...')`
 		return ast.void_type

vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.vv:3:21: error: undefined ident: `time.secondz`.
+Did you mean `time.second`?
+    1 | import time
+    2 | 
+    3 | time.sleep(1 * time.secondz)
+      |                     ~~~~~~~

vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.vv

@@ -0,0 +1,3 @@
+import time
+
+time.sleep(1 * time.secondz)