From 440080a2959590eb4b46c7aa9f0fc86d9d02bcce Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 26 Feb 2026 10:03:20 +0300
Subject: [PATCH] parser: support `.to_fixed_size()` method on array literals
 (fixes #22849)

---
 doc/docs.md                                   |  3 ++-
 vlib/v/ast/ast.v                              | 25 ++++++++++---------
 vlib/v/fmt/fmt.v                              |  6 ++++-
 vlib/v/parser/parser.v                        | 16 ++++++++++++
 .../fixed_array_to_fixed_size_method_test.v   | 14 +++++++++++
 5 files changed, 50 insertions(+), 14 deletions(-)
 create mode 100644 vlib/v/tests/builtin_arrays/fixed_array_to_fixed_size_method_test.v

diff --git a/doc/docs.md b/doc/docs.md
index 890ff741d..52cd8916c 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -1409,7 +1409,8 @@ fnums[2] = 100
 println(fnums) // => [1, 10, 100]
 println(typeof(fnums).name) // => [3]int
 
-fnums2 := [1, 10, 100]! // short init syntax that does the same (the syntax will probably change)
+fnums2 := [1, 10, 100].to_fixed_size() // explicit conversion syntax
+fnums3 := [1, 10, 100]! // short init syntax, equivalent to `.to_fixed_size()`
 
 anums := fnums[..] // same as `anums := fnums[0..fnums.len]`
 println(anums) // => [1, 10, 100]
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index bcdc55407..a0271c3bd 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -1693,18 +1693,19 @@ pub:
 @[minify]
 pub struct ArrayInit {
 pub:
-	pos           token.Pos   // `[]` in []Type{} position
-	elem_type_pos token.Pos   // `Type` in []Type{} position
-	ecmnts        [][]Comment // optional iembed comments after each expr
-	pre_cmnts     []Comment
-	is_fixed      bool
-	is_option     bool // true if it was declared as ?[2]Type or ?[]Type
-	has_val       bool // fixed size literal `[expr, expr]!`
-	mod           string
-	has_len       bool
-	has_cap       bool
-	has_init      bool
-	has_index     bool // true if temp variable index is used
+	pos                token.Pos   // `[]` in []Type{} position
+	elem_type_pos      token.Pos   // `Type` in []Type{} position
+	ecmnts             [][]Comment // optional iembed comments after each expr
+	pre_cmnts          []Comment
+	is_fixed           bool
+	is_option          bool // true if it was declared as ?[2]Type or ?[]Type
+	has_val            bool // fixed size literal `[expr, expr]!`
+	from_to_fixed_size bool // lowered from `[expr, expr].to_fixed_size()`
+	mod                string
+	has_len            bool
+	has_cap            bool
+	has_init           bool
+	has_index          bool // true if temp variable index is used
 pub mut:
 	exprs        []Expr // `[expr, expr]` or `[expr]Type{}` for fixed array
 	len_expr     Expr   // len: expr
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index 9364f493d..000f6a273 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -2008,7 +2008,11 @@ pub fn (mut f Fmt) array_init(node ast.ArrayInit) {
 	// `[100]u8`
 	if node.is_fixed {
 		if node.has_val {
-			f.write('!')
+			if node.from_to_fixed_size {
+				f.write('.to_fixed_size()')
+			} else {
+				f.write('!')
+			}
 			return
 		}
 		f.write(f.type_to_str_using_aliases(node.elem_type, f.mod2alias))
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 8ea0f38c2..640a97e20 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -2255,6 +2255,22 @@ fn (mut p Parser) dot_expr(left ast.Expr) ast.Expr {
 		or_block := p.gen_or_block()
 		end_pos := p.prev_tok.pos()
 		pos := name_pos.extend(end_pos)
+		if field_name == 'to_fixed_size' && left is ast.ArrayInit && args.len == 0
+			&& or_block.kind == .absent {
+			left_array := left as ast.ArrayInit
+			if left_array.is_fixed {
+				return left_array
+			}
+			if left_array.exprs.len > 0 {
+				return ast.ArrayInit{
+					...left_array
+					is_fixed:           true
+					has_val:            true
+					from_to_fixed_size: true
+					pos:                left_array.pos.extend(end_pos)
+				}
+			}
+		}
 		comments := p.eat_comments(same_line: true)
 		mut left_node := unsafe { left }
 		if mut left_node is ast.CallExpr {
diff --git a/vlib/v/tests/builtin_arrays/fixed_array_to_fixed_size_method_test.v b/vlib/v/tests/builtin_arrays/fixed_array_to_fixed_size_method_test.v
new file mode 100644
index 000000000..3e2fa98f7
--- /dev/null
+++ b/vlib/v/tests/builtin_arrays/fixed_array_to_fixed_size_method_test.v
@@ -0,0 +1,14 @@
+fn make_fixed() ![3]int {
+	return [1, 10, 110].to_fixed_size()
+}
+
+fn test_array_literal_to_fixed_size_method() {
+	fnums := [1, 10, 110].to_fixed_size()
+	assert fnums == [1, 10, 110]!
+	assert typeof(fnums).name == '[3]int'
+}
+
+fn test_array_literal_to_fixed_size_method_with_result_propagation() ! {
+	fnums := make_fixed()!
+	assert fnums == [1, 10, 110]!
+}
-- 
2.39.5