From c8226275316ca3f7dc62c00a017754467f2ba4f1 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 14 Apr 2026 12:45:34 +0300
Subject: [PATCH] checker: Add support for generic struct params (fixes #24191)

---
 vlib/v/checker/struct.v                       | 32 ++++++++++++++-----
 ...eneric_fn_short_syntax_struct_param_test.v | 18 +++++++++++
 2 files changed, 42 insertions(+), 8 deletions(-)
 create mode 100644 vlib/v/tests/generics/generic_fn_short_syntax_struct_param_test.v

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index f076f72ae..a3a9fe768 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -498,7 +498,13 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 		c.expected_type = old_expected_type
 		util.timing_measure_cumulative(@METHOD)
 	}
-	source_typ := if node.is_short_syntax && c.expected_type != ast.void_type {
+	short_syntax_expected_type_sym := c.table.sym(c.unwrap_generic(c.expected_type))
+	short_syntax_infers_anon_from_generic_param := node.is_short_syntax && node.typ == ast.void_type
+		&& c.expected_type != ast.void_type && c.expected_type.has_flag(.generic)
+		&& short_syntax_expected_type_sym.kind == .any
+		&& !short_syntax_expected_type_sym.is_builtin()
+	source_typ := if node.is_short_syntax && c.expected_type != ast.void_type
+		&& !short_syntax_infers_anon_from_generic_param {
 		c.expected_type
 	} else if node.typ != ast.void_type {
 		node.typ
@@ -515,7 +521,7 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 		source_generic_typ = source_sym.info.parent_type.derive(source_typ).set_flag(.generic)
 	}
 	if node.generic_typ == 0 && source_generic_typ != ast.void_type
-		&& (source_generic_typ.has_flag(.generic)
+		&& !short_syntax_infers_anon_from_generic_param && (source_generic_typ.has_flag(.generic)
 		|| c.type_has_unresolved_generic_parts(source_generic_typ)) {
 		node.generic_typ = source_generic_typ
 	}
@@ -551,11 +557,15 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 			c.error('unexpected short struct syntax', node.pos)
 			return ast.void_type
 		}
-		sym := c.table.sym(c.expected_type)
-		if sym.kind == .array {
-			node.typ = c.table.value_type(c.expected_type)
+		if short_syntax_infers_anon_from_generic_param {
+			node.typ = ast.none_type
 		} else {
-			node.typ = c.expected_type
+			sym := c.table.sym(c.expected_type)
+			if sym.kind == .array {
+				node.typ = c.table.value_type(c.expected_type)
+			} else {
+				node.typ = c.expected_type
+			}
 		}
 	}
 	original_node_typ := node.typ
@@ -1124,7 +1134,7 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 			mut init_fields := []ast.StructField{}
 			for mut init_field in node.init_fields {
 				mut expr := unsafe { init_field }
-				init_field.typ = c.expr(mut expr.expr)
+				init_field.typ = ast.mktyp(c.expr(mut expr.expr))
 				init_field.expected_type = init_field.typ
 				init_fields << ast.StructField{
 					name:   init_field.name
@@ -1148,7 +1158,13 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 			}
 			ret := c.table.register_sym(sym_struct)
 			c.table.register_anon_struct(name, ret)
-			node.typ = c.table.find_type_idx(name)
+			node = ast.StructInit{
+				...node
+				typ:             c.table.find_type_idx(name)
+				typ_str:         name
+				is_anon:         true
+				is_short_syntax: false
+			}
 		}
 		else {}
 	}
diff --git a/vlib/v/tests/generics/generic_fn_short_syntax_struct_param_test.v b/vlib/v/tests/generics/generic_fn_short_syntax_struct_param_test.v
new file mode 100644
index 000000000..e0ecd1909
--- /dev/null
+++ b/vlib/v/tests/generics/generic_fn_short_syntax_struct_param_test.v
@@ -0,0 +1,18 @@
+fn query_short_syntax_struct_arg[T](query_config T) (int, string) {
+	mut a := 0
+	mut b := ''
+	$for field in T.fields {
+		$if field.typ is int {
+			a = query_config.$(field.name)
+		} $else $if field.typ is string {
+			b = query_config.$(field.name)
+		}
+	}
+	return a, b
+}
+
+fn test_generic_fn_short_syntax_struct_param() {
+	a, b := query_short_syntax_struct_arg(a: 1, b: 'hello')
+	assert a == 1
+	assert b == 'hello'
+}
-- 
2.39.5