From 9184983d06c103c470ace35390066fb017c66b11 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 23 Apr 2026 21:55:42 +0300
Subject: [PATCH] =?UTF-8?q?fmt:=20fix=20`parser`:=20anonymous=20struct=20t?=
 =?UTF-8?q?ype=20literal=20not=20accepted=20as=20a=20generic=20type=20argu?=
 =?UTF-8?q?ment=20(`fn[struct=20{=20=E2=80=A6=20}](=E2=80=A6)`)=20(fixes?=
 =?UTF-8?q?=20#26894)?=
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---
 vlib/v/fmt/fmt.v       | 26 +++++++++++++++-----------
 vlib/v/fmt/struct.v    | 11 +++++++++++
 vlib/v/parser/checks.v | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 11 deletions(-)

diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index f8d7b03b4..ae82c1529 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -2245,17 +2245,19 @@ fn (mut f Fmt) write_generic_call_if_require(node ast.CallExpr) {
 	if node.concrete_types.len > 0 {
 		f.write('[')
 		for i, concrete_type in node.concrete_types {
-			mut name := f.type_to_str_using_aliases(concrete_type, f.mod2alias)
 			tsym := f.table.sym(concrete_type)
-			if tsym.language != .js && !tsym.name.starts_with('JS.') {
-				name = f.short_module(name)
-			} else if tsym.language == .js && !tsym.name.starts_with('JS.') {
-				name = 'JS.' + name
-			}
-			if tsym.language == .c {
-				name = 'C.' + name
+			if !f.write_anon_struct_type(concrete_type) {
+				mut name := f.type_to_str_using_aliases(concrete_type, f.mod2alias)
+				if tsym.language != .js && !tsym.name.starts_with('JS.') {
+					name = f.short_module(name)
+				} else if tsym.language == .js && !tsym.name.starts_with('JS.') {
+					name = 'JS.' + name
+				}
+				if tsym.language == .c {
+					name = 'C.' + name
+				}
+				f.write(name)
 			}
-			f.write(name)
 			if i != node.concrete_types.len - 1 {
 				f.write(', ')
 			}
@@ -2504,8 +2506,10 @@ pub fn (mut f Fmt) ident(node ast.Ident) {
 		if node.concrete_types.len > 0 {
 			f.write('[')
 			for i, concrete_type in node.concrete_types {
-				typ_name := f.type_to_str_using_aliases(concrete_type, f.mod2alias)
-				f.write(typ_name)
+				if !f.write_anon_struct_type(concrete_type) {
+					typ_name := f.type_to_str_using_aliases(concrete_type, f.mod2alias)
+					f.write(typ_name)
+				}
 				if i != node.concrete_types.len - 1 {
 					f.write(', ')
 				}
diff --git a/vlib/v/fmt/struct.v b/vlib/v/fmt/struct.v
index d0e462aa2..01157db45 100644
--- a/vlib/v/fmt/struct.v
+++ b/vlib/v/fmt/struct.v
@@ -198,6 +198,17 @@ fn (mut f Fmt) write_anon_struct_field_decl(field_typ ast.Type, field_anon_decl
 	return false
 }
 
+fn (mut f Fmt) write_anon_struct_type(typ ast.Type) bool {
+	sym := f.table.sym(typ)
+	if sym.info is ast.Struct && sym.info.is_anon {
+		f.struct_decl(ast.StructDecl{
+			fields: sym.info.fields
+		}, true)
+		return true
+	}
+	return false
+}
+
 pub fn (mut f Fmt) struct_init(node ast.StructInit) {
 	struct_init_save := f.is_struct_init
 	f.is_struct_init = true
diff --git a/vlib/v/parser/checks.v b/vlib/v/parser/checks.v
index 9480df2b3..3e8bc1bc6 100644
--- a/vlib/v/parser/checks.v
+++ b/vlib/v/parser/checks.v
@@ -117,12 +117,48 @@ fn (mut p Parser) is_following_concrete_types() bool {
 	return true
 }
 
+@[direct_array_access]
+fn (p &Parser) is_anon_struct_generic_arg(next_kind token.Kind) bool {
+	mut i := 2
+	mut nested_sbr_count := 0
+	mut nested_cbr_count := 0
+	for {
+		cur_tok := p.peek_token(i)
+		if cur_tok.kind == .eof {
+			return false
+		}
+		if cur_tok.kind == .lsbr {
+			nested_sbr_count++
+		} else if cur_tok.kind == .rsbr {
+			if nested_cbr_count == 0 && nested_sbr_count == 0 {
+				return p.peek_token(i + 1).kind == next_kind
+			}
+			if nested_sbr_count == 0 {
+				return false
+			}
+			nested_sbr_count--
+		} else if cur_tok.kind == .lcbr {
+			nested_cbr_count++
+		} else if cur_tok.kind == .rcbr {
+			if nested_cbr_count == 0 {
+				return false
+			}
+			nested_cbr_count--
+		}
+		i++
+	}
+	return false
+}
+
 @[direct_array_access]
 fn (p &Parser) is_generic_struct_init() bool {
 	lit0_is_capital := p.tok.kind != .eof && p.tok.lit.len > 0 && p.tok.lit[0].is_capital()
 	if !lit0_is_capital || p.peek_tok.kind != .lsbr {
 		return false
 	}
+	if p.peek_token(2).kind == .key_struct {
+		return p.is_anon_struct_generic_arg(.lcbr)
+	}
 	mut i := 2
 	mut nested_sbr_count := 0
 	for {
@@ -191,6 +227,9 @@ fn (p &Parser) is_generic_call() bool {
 		// case 1 (array or fixed array type)
 		return tok3.kind == .rsbr || (tok4.kind == .rsbr && p.is_typename(tok5))
 	}
+	if kind2 == .key_struct {
+		return p.is_anon_struct_generic_arg(.lpar)
+	}
 
 	if kind2 == .name {
 		if kind3 == .lsbr && tok2.lit == 'map' {
-- 
2.39.5