From d67f4d0234729b018c633ddd9e59e7e6e9da8380 Mon Sep 17 00:00:00 2001
From: larpon <768942+larpon@users.noreply.github.com>
Date: Thu, 27 Jun 2024 07:27:43 +0200
Subject: [PATCH] checker: add error for `field [$d('x', 2)]int = [1, 2]!`
 (#21741)

---
 vlib/v/checker/struct.v                                  | 9 +++++++++
 .../struct_field_fixed_size_init_with_d_as_size_err.out  | 7 +++++++
 .../struct_field_fixed_size_init_with_d_as_size_err.vv   | 6 ++++++
 3 files changed, 22 insertions(+)
 create mode 100644 vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.out
 create mode 100644 vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.vv

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 9327da75b..88d81d7cf 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -199,6 +199,15 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 				if !field.typ.has_flag(.option) && !field.typ.has_flag(.result) {
 					c.check_expr_option_or_result_call(field.default_expr, field.default_expr_typ)
 				}
+				if sym.info is ast.ArrayFixed && field.typ == field.default_expr_typ {
+					if sym.info.size_expr is ast.ComptimeCall {
+						// field [$d('x' ,2)]int = [1 ,2]!
+						if sym.info.size_expr.method_name == 'd' {
+							c.error('cannot initialize a fixed size array field that uses `\$d()` as size quantifier since the size may change via -d',
+								field.default_expr.pos())
+						}
+					}
+				}
 				interface_implemented := sym.kind == .interface_
 					&& c.type_implements(field.default_expr_typ, field.typ, field.pos)
 				c.check_expected(field.default_expr_typ, field.typ) or {
diff --git a/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.out b/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.out
new file mode 100644
index 000000000..e62bef668
--- /dev/null
+++ b/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.vv:3:31: error: cannot initialize a fixed size array field that uses `$d()` as size quantifier since the size may change via -d
+    1 | struct Gin {
+    2 | mut:
+    3 |     juice [$d('amount', 4)]int = [1, 2, 3, 4]!
+      |                                  ~~~~~~~~~~~~~
+    4 | }
+    5 |
\ No newline at end of file
diff --git a/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.vv b/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.vv
new file mode 100644
index 000000000..929ed1911
--- /dev/null
+++ b/vlib/v/checker/tests/struct_field_fixed_size_init_with_d_as_size_err.vv
@@ -0,0 +1,6 @@
+struct Gin {
+mut:
+	juice [$d('amount', 4)]int = [1, 2, 3, 4]!
+}
+
+fn main() {}
-- 
2.39.5