From 4be7ab216ddefec124eaa79c11e45413b7fca294 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 11 Mar 2026 15:51:46 +0300
Subject: [PATCH] math: decimal data type (fixes #21754)

---
 doc/docs.md                                         |  8 ++++++++
 vlib/v/checker/struct.v                             | 13 +++++--------
 .../v/tests/aliases/numeric_alias_empty_init_test.v | 12 ++++++++++++
 3 files changed, 25 insertions(+), 8 deletions(-)
 create mode 100644 vlib/v/tests/aliases/numeric_alias_empty_init_test.v

diff --git a/doc/docs.md b/doc/docs.md
index 228129ae8..c3ce6308a 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -3624,6 +3624,14 @@ To define a new type `NewType` as an alias for `ExistingType`,
 do `type NewType = ExistingType`.<br/>
 This is a special case of a [sum type](#sum-types) declaration.
 
+Numeric aliases can use empty literal syntax for zero/default initialization:
+
+```v
+type Decimal = f64
+
+amount := Decimal{}
+```
+
 ### Enums
 
 An enum is a group of constant integer values, each having its own name,
diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index c9ef1bb51..29313411c 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -614,12 +614,6 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 	if type_sym.kind == .interface && type_sym.language != .js {
 		c.error('cannot instantiate interface `${type_sym.name}`', node.pos)
 	}
-	if type_sym.info is ast.Alias {
-		if type_sym.info.parent_type.is_number() {
-			c.error('cannot instantiate number type alias `${type_sym.name}`', node.pos)
-			return ast.void_type
-		}
-	}
 	// allow init structs from generic if they're private except the type is from builtin module
 	if !node.has_update_expr && !type_sym.is_pub && type_sym.kind != .placeholder
 		&& type_sym.language != .c && (type_sym.mod != c.mod && !(node.typ.has_flag(.generic)
@@ -686,7 +680,7 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 			mut info := ast.Struct{}
 			if type_sym.kind == .alias {
 				info_t := type_sym.info as ast.Alias
-				sym := c.table.sym(info_t.parent_type)
+				sym := c.table.final_sym(info_t.parent_type)
 				if sym.kind == .placeholder { // pending import symbol did not resolve
 					c.error('unknown struct: ${type_sym.name}', node.pos)
 					return ast.void_type
@@ -699,7 +693,10 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 						// we do allow []int{}, [10]int{}, map[string]int{}
 					}
 					else {
-						c.error('alias type name: ${sym.name} is not struct type', node.pos)
+						if !(sym.is_number() && node.init_fields.len == 0 && !node.has_update_expr) {
+							c.error('alias type name: ${sym.name} is not struct type',
+								node.pos)
+						}
 					}
 				}
 			} else {
diff --git a/vlib/v/tests/aliases/numeric_alias_empty_init_test.v b/vlib/v/tests/aliases/numeric_alias_empty_init_test.v
new file mode 100644
index 000000000..22bbe929f
--- /dev/null
+++ b/vlib/v/tests/aliases/numeric_alias_empty_init_test.v
@@ -0,0 +1,12 @@
+type Decimal = f64
+type Counter = int
+
+fn test_empty_init_of_numeric_aliases() {
+	decimal_zero := Decimal{}
+	counter_zero := Counter{}
+
+	assert typeof(decimal_zero).name == 'Decimal'
+	assert typeof(counter_zero).name == 'Counter'
+	assert decimal_zero == Decimal(0.0)
+	assert counter_zero == Counter(0)
+}
-- 
2.39.5