From 031d77523ddbe69a43bb988d34b41577d8c07d33 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 23 Apr 2026 21:07:24 +0300
Subject: [PATCH] cgen: fix V panic: as cast: cannot cast `v.ast.FnType` to
 `v.ast.Struct` (fixes #26944)

---
 vlib/v/gen/c/struct.v                         | 67 +++++++++++++------
 .../tests/structs/struct_embed_fn_type_test.v |  6 ++
 2 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index 47a11a65c..e46b0c72d 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -289,34 +289,57 @@ fn (mut g Gen) struct_init(node ast.StructInit) {
 				embed_sym := g.table.sym(embed)
 				embed_name := embed_sym.embed_name()
 				if embed_name !in inited_fields {
-					embed_info := if embed_sym.info is ast.Struct {
-						embed_sym.info
+					mut embed_info := ast.Struct{}
+					mut has_embed_struct_info := false
+					if embed_sym.info is ast.Struct {
+						embed_info = embed_sym.info
+						has_embed_struct_info = true
 					} else {
-						g.table.final_sym(embed).info as ast.Struct
-					}
-					embed_field_names := embed_info.fields.map(it.name)
-					fields_to_embed := init_fields_to_embed.filter(it.name !in used_embed_fields
-						&& it.name in embed_field_names)
-					used_embed_fields << fields_to_embed.map(it.name)
-					default_init := ast.StructInit{
-						...node
-						typ:             embed
-						is_update_embed: true
-						init_fields:     init_fields_to_embed
+						final_embed_sym := g.table.final_sym(embed)
+						if final_embed_sym.info is ast.Struct {
+							embed_info = final_embed_sym.info
+							has_embed_struct_info = true
+						}
 					}
-					inside_cast_in_heap := g.inside_cast_in_heap
-					g.inside_cast_in_heap = 0 // prevent use of pointers in child structs
+					if has_embed_struct_info {
+						embed_field_names := embed_info.fields.map(it.name)
+						fields_to_embed := init_fields_to_embed.filter(
+							it.name !in used_embed_fields && it.name in embed_field_names)
+						used_embed_fields << fields_to_embed.map(it.name)
+						default_init := ast.StructInit{
+							...node
+							typ:             embed
+							is_update_embed: true
+							init_fields:     init_fields_to_embed
+						}
+						inside_cast_in_heap := g.inside_cast_in_heap
+						g.inside_cast_in_heap = 0 // prevent use of pointers in child structs
 
-					g.write('.${embed_name} = ')
-					g.struct_init(default_init)
+						g.write('.${embed_name} = ')
+						g.struct_init(default_init)
 
-					g.inside_cast_in_heap = inside_cast_in_heap // restore value for further struct inits
-					if is_multiline {
-						g.writeln(',')
+						g.inside_cast_in_heap = inside_cast_in_heap // restore value for further struct inits
+						if is_multiline {
+							g.writeln(',')
+						} else {
+							g.write(',')
+						}
+						initialized = true
 					} else {
-						g.write(',')
+						// Embedded fn/interface/alias fields do not have child fields to recurse into.
+						if g.zero_struct_field(ast.StructField{
+							name: embed_name
+							typ:  embed
+						})
+						{
+							if is_multiline {
+								g.writeln(',')
+							} else {
+								g.write(',')
+							}
+							initialized = true
+						}
 					}
-					initialized = true
 				}
 			}
 			g.is_shared = old_is_shared2
diff --git a/vlib/v/tests/structs/struct_embed_fn_type_test.v b/vlib/v/tests/structs/struct_embed_fn_type_test.v
index 4bca7712c..324768ac6 100644
--- a/vlib/v/tests/structs/struct_embed_fn_type_test.v
+++ b/vlib/v/tests/structs/struct_embed_fn_type_test.v
@@ -72,3 +72,9 @@ fn test_embed_named_fn_type_promotes_methods() {
 	assert one == 'one'
 	assert more == 'more'
 }
+
+fn test_embed_named_fn_type_zero_init() {
+	mut cmd := CommandSet{}
+	cmd.CommandFn = run_command
+	assert cmd.one() == 'one'
+}
-- 
2.39.5