ast,fmt: further improve type detection of user defined typenames, ex…

…tend tests (#21004)

vlib/v/ast/types.v

@@ -1471,28 +1471,33 @@ fn (t Table) shorten_user_defined_typenames(original_name string, import_aliases
 	if alias := import_aliases[original_name] {
 		return alias
 	}
-	mut parts := original_name.split('.')
-	if parts.len > 1 {
-		// mod.submod.submod2.Type => submod2.Type
-		if !parts[..parts.len - 1].any(it.contains('[')) {
-			mod_idx := parts.len - 2
-			if t.is_fmt {
-				parts[mod_idx] = original_name.all_before_last('.')
-			}
-			if alias := import_aliases[parts[mod_idx]] {
-				parts[mod_idx] = alias
-			} else if t.cmod_prefix != '' && original_name.starts_with(t.cmod_prefix) {
+	mut mod, mut typ := original_name.rsplit_once('.') or { return original_name }
+	if !mod.contains('[') {
+		if !t.is_fmt {
+			mod = mod.all_after_last('.')
+		}
+		if alias := import_aliases[mod] {
+			mod = alias
+		} else if t.cmod_prefix != '' {
+			if alias := import_aliases[t.cmod_prefix + mod] {
+				mod = alias
+			} else {
 				// cur_mod.Type => Type
 				return original_name.all_after(t.cmod_prefix)
 			}
-			return parts[mod_idx..].join('.')
 		}
-		if original_name.contains('[]') {
-			// []mod.name
-			return original_name.all_after('.')
+	}
+	// E.g.: []mod.Type => []Type; []mod.submod.Type => []submod.Type;
+	// imported_mod.Type[mod.Result[[]mod.Token]] => imported_mod.Type[Result[[]Token]]
+	if original_name.contains('[]') {
+		if lhs, typ_after_lsbr := original_name.split_once('[') {
+			if mod_, typ_before_lsbr := lhs.rsplit_once('.') {
+				mod = mod_
+				typ = '${typ_before_lsbr}[${typ_after_lsbr}'
+			}
 		}
 	}
-	return original_name
+	return '${mod}.${typ}'
 }
 
 @[minify]

vlib/v/checker/tests/check_err_msg_with_generics.out

@@ -1,6 +1,6 @@
-vlib/v/checker/tests/check_err_msg_with_generics.vv:15:10: error: cannot cast struct `BSTree[Result[[]Token, Err[string]]]` to `int`
+vlib/v/checker/tests/check_err_msg_with_generics.vv:15:10: error: cannot cast struct `datatypes.BSTree[Result[[]Token, Err[string]]]` to `int`
    13 | fn test_err_msg() {
    14 |     typ := datatypes.BSTree[Result[[]Token, Err[string]]]{}
    15 |     println(int(typ))
       |             ~~~~~~~~
-   16 | }
+   16 | }

vlib/v/fmt/fmt_test.v

@@ -73,10 +73,9 @@ fn test_fmt() {
 	run_fmt(mut input_files)
 }
 
-// NOTE: enable with upcommming `__input.vv` / `__expected.vv` files for vmodules
-/* fn test_fmt_vmodules() {
+fn test_fmt_vmodules() {
 	vmodules_tdir := os.join_path(vroot, 'vlib', 'v', 'fmt', 'testdata', 'vmodules')
 	os.setenv('VMODULES', vmodules_tdir, true)
 	mut input_files := os.walk_ext(vmodules_tdir, '_input.vv')
 	run_fmt(mut input_files)
-} */
+}

vlib/v/fmt/testdata/vmodules/submod_type_alias/submod_type_alias_input.vv

@@ -0,0 +1,7 @@
+// The module name has to match the modules dir name.
+module submod_type_alias
+
+// The submod dir structure that is imported has to be existent.
+import bar.baz
+
+type MyAlias = bar.baz.Baz