From b29982205a0410b4e3d30f6e5b82851ceb2071d9 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 15 Apr 2026 15:48:08 +0300
Subject: [PATCH] cgen: fix c error when building gui library (fixes #26861)

---
 vlib/v/gen/c/cgen.v                           | 28 +++++++++++--
 ...ption_autoheap_selector_none_unwrap_test.v | 42 +++++++++++++++++++
 2 files changed, 67 insertions(+), 3 deletions(-)
 create mode 100644 vlib/v/tests/options/option_autoheap_selector_none_unwrap_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 6068aaaa5..4b5b0bb69 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -6255,10 +6255,32 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 	}
 	mut expr_is_auto_heap := node.expr is ast.Ident && g.resolved_ident_is_auto_heap(node.expr)
 	mut expr_is_unwrapped_autoheap_option := false
+	mut expr_autoheap_option_type := ast.Type(0)
 	if expr_is_auto_heap {
 		expr_ident := node.expr as ast.Ident
-		if expr_ident.obj is ast.Var && expr_ident.obj.typ.has_flag(.option)
-			&& !lhs_expr_type.has_flag(.option) {
+		if node.expr_type.has_flag(.option) {
+			expr_autoheap_option_type = node.expr_type
+		}
+		if expr_ident.obj is ast.Var {
+			if expr_ident.obj.orig_type.has_flag(.option) {
+				expr_autoheap_option_type = expr_ident.obj.orig_type
+			} else if expr_ident.obj.typ.has_flag(.option) {
+				expr_autoheap_option_type = expr_ident.obj.typ
+			}
+		}
+		if expr_autoheap_option_type == 0 && selector_scope != unsafe { nil } {
+			if scope_var := selector_scope.find_var(expr_ident.name) {
+				if scope_var.orig_type.has_flag(.option) {
+					expr_autoheap_option_type = scope_var.orig_type
+				} else if scope_var.typ.has_flag(.option) {
+					expr_autoheap_option_type = scope_var.typ
+				}
+			}
+		}
+		// Autoheap option locals can have their runtime type smartcast down to the
+		// unwrapped struct before selector codegen runs. Preserve the original
+		// option source type so selector receivers still unwrap through `->data`.
+		if expr_autoheap_option_type.has_flag(.option) && !lhs_expr_type.has_flag(.option) {
 			expr_is_unwrapped_autoheap_option = true
 			expr_is_auto_heap = false
 		}
@@ -6301,7 +6323,7 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 		} else {
 			g.get_ternary_name(c_name(expr_ident.name))
 		}
-		g.unwrap_option_type(expr_ident.obj.typ, expr_name, true)
+		g.unwrap_option_type(expr_autoheap_option_type, expr_name, true)
 	} else if expr_is_auto_heap {
 		expr_ident := node.expr as ast.Ident
 		if expr_ident.obj is ast.Var && expr_ident.obj.is_inherited {
diff --git a/vlib/v/tests/options/option_autoheap_selector_none_unwrap_test.v b/vlib/v/tests/options/option_autoheap_selector_none_unwrap_test.v
new file mode 100644
index 000000000..ea7485b3f
--- /dev/null
+++ b/vlib/v/tests/options/option_autoheap_selector_none_unwrap_test.v
@@ -0,0 +1,42 @@
+struct Padding {
+	top    f32
+	bottom f32
+}
+
+fn (p Padding) height() f32 {
+	return p.top + p.bottom
+}
+
+struct Shape {
+	height  f32
+	padding Padding
+}
+
+@[heap]
+struct Layout {
+	shape &Shape
+}
+
+fn find_layout(layout &Layout) ?Layout {
+	return *layout
+}
+
+fn test_autoheap_option_selector_none_unwrap() {
+	shape := &Shape{
+		height:  7
+		padding: Padding{
+			top:    1
+			bottom: 2
+		}
+	}
+	layout := &Layout{
+		shape: shape
+	}
+	layout_scroll := find_layout(layout)
+	if layout_scroll != none {
+		layout_scroll_height := layout_scroll.shape.height - layout_scroll.shape.padding.height()
+		assert layout_scroll_height == 4
+	} else {
+		assert false
+	}
+}
-- 
2.39.5