markused: fix compilation of gg programs with -skip-unused, add test to prevent regressions (#15821)

cmd/tools/vtest-all.v

@@ -169,6 +169,11 @@ fn get_all_commands() []Command {
 			okmsg: 'V compiles hello_world.v on the JS backend, with -skip-unused'
 			rmfile: 'hw_skip_unused.js'
 		}
+		res << Command{
+			line: '$vexe -skip-unused examples/2048'
+			okmsg: 'V can compile 2048 with -skip-unused.'
+			rmfile: 'examples/2048/2048'
+		}
 	}
 	res << Command{
 		line: '$vexe -o vtmp cmd/v'

cmd/tools/vtest-self.v

@@ -155,6 +155,7 @@ const (
 	skip_on_musl                  = [
 		'vlib/v/tests/profile/profile_test.v',
 		'vlib/gg/draw_fns_api_test.v',
+		'vlib/v/tests/skip_unused/gg_code.vv',
 	]
 	skip_on_ubuntu_musl           = [
 		//'vlib/v/gen/js/jsgen_test.v',

vlib/v/compiler_errors_test.v

@@ -19,6 +19,11 @@ const skip_on_cstrict = [
 const skip_on_ubuntu_musl = [
 	'vlib/v/checker/tests/vweb_tmpl_used_var.vv',
 	'vlib/v/checker/tests/vweb_routing_checks.vv',
+	'vlib/v/tests/skip_unused/gg_code.vv',
+]
+
+const skip_on_ci_musl = [
+	'vlib/v/tests/skip_unused/gg_code.vv',
 ]
 
 const vexe = os.getenv('VEXE')
@@ -37,6 +42,8 @@ const github_job = os.getenv('GITHUB_JOB')
 
 const v_ci_ubuntu_musl = os.getenv('V_CI_UBUNTU_MUSL').len > 0
 
+const v_ci_musl = os.getenv('V_CI_MUSL').len > 0
+
 const v_ci_cstrict = os.getenv('V_CI_CSTRICT').len > 0
 
 struct TaskDescription {
@@ -217,6 +224,9 @@ fn (mut tasks Tasks) run() {
 	if v_ci_ubuntu_musl {
 		m_skip_files << skip_on_ubuntu_musl
 	}
+	if v_ci_musl {
+		m_skip_files << skip_on_ci_musl
+	}
 	if v_ci_cstrict {
 		m_skip_files << skip_on_cstrict
 	}

vlib/v/markused/walker.v

@@ -13,6 +13,7 @@ pub mut:
 	used_fns     map[string]bool // used_fns['println'] == true
 	used_consts  map[string]bool // used_consts['os.args'] == true
 	used_globals map[string]bool
+	used_structs map[string]bool
 	n_asserts    int
 	pref         &pref.Preferences = unsafe { nil }
 mut:
@@ -402,17 +403,7 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 			sym := w.table.sym(node.typ)
 			if sym.kind == .struct_ {
 				info := sym.info as ast.Struct
-				for ifield in info.fields {
-					if ifield.has_default_expr {
-						w.expr(ifield.default_expr)
-					}
-					if ifield.typ != 0 {
-						fsym := w.table.sym(ifield.typ)
-						if fsym.kind == .map {
-							w.table.used_maps++
-						}
-					}
-				}
+				w.a_struct_info(sym.name, info)
 			}
 			if node.has_update_expr {
 				w.expr(node.update_expr)
@@ -463,6 +454,27 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 	}
 }
 
+pub fn (mut w Walker) a_struct_info(sname string, info ast.Struct) {
+	if sname in w.used_structs {
+		return
+	}
+	w.used_structs[sname] = true
+	for ifield in info.fields {
+		if ifield.has_default_expr {
+			w.expr(ifield.default_expr)
+		}
+		if ifield.typ != 0 {
+			fsym := w.table.sym(ifield.typ)
+			if fsym.kind == .map {
+				w.table.used_maps++
+			}
+			if fsym.kind == .struct_ {
+				w.a_struct_info(fsym.name, fsym.struct_info())
+			}
+		}
+	}
+}
+
 pub fn (mut w Walker) fn_decl(mut node ast.FnDecl) {
 	if node.language == .c {
 		return

vlib/v/tests/skip_unused/gg_code.run.out

@@ -0,0 +1 @@
+OK

vlib/v/tests/skip_unused/gg_code.skip_unused.run.out

@@ -0,0 +1 @@
+OK

vlib/v/tests/skip_unused/gg_code.vv

@@ -0,0 +1,23 @@
+module main
+
+import gg
+import gx
+
+[console]
+fn main() {
+	x := gg.new_context(
+		bg_color: gx.rgb(174, 198, 255)
+		window_title: 'GG Hello'
+		frame_fn: fn (mut ctx gg.Context) {
+			ctx.begin()
+			ctx.draw_text_def(10, 25, 'Hello')
+			ctx.end()
+			if ctx.frame > 10 {
+				println('OK')
+				exit(0)
+			}
+		}
+	)
+	_ := x.user_data
+	println('OK')
+}