checker: fix and cleanup uninitialized checks for array initialisers …

…with `len:` (fix #20272) (#20279)

vlib/v/checker/containers.v

@@ -7,6 +7,7 @@ import v.token
 
 fn (mut c Checker) array_init(mut node ast.ArrayInit) ast.Type {
 	mut elem_type := ast.void_type
+	unwrap_elem_type := c.unwrap_generic(node.elem_type)
 	// `x := []string{}` (the type was set in the parser)
 	if node.typ != ast.void_type {
 		if node.elem_type != 0 {
@@ -76,14 +77,13 @@ fn (mut c Checker) array_init(mut node ast.ArrayInit) ast.Type {
 			if len_typ.has_flag(.option) {
 				c.error('cannot use unwrapped Option as length', node.len_expr.pos())
 			}
-			if node.has_len && !node.has_init {
-				elem_type_sym := c.table.sym(node.elem_type)
-				if elem_type_sym.kind == .interface_ {
-					c.error('cannot instantiate an array of interfaces without also giving a default `init:` value',
-						node.len_expr.pos())
+			// check &int{}, interface, sum_type initialized
+			if !node.has_init {
+				c.check_elements_initialized(unwrap_elem_type) or {
+					c.warn('${err.msg()}, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)',
+						node.pos)
 				}
 			}
-			c.ensure_sumtype_array_has_default_value(node)
 		}
 		if node.has_cap {
 			cap_typ := c.check_expr_opt_call(node.cap_expr, c.expr(mut node.cap_expr))
@@ -97,26 +97,21 @@ fn (mut c Checker) array_init(mut node ast.ArrayInit) ast.Type {
 			c.error('generic struct cannot be used in non-generic function', node.pos)
 		}
 
-		// `&int{}` check
-		if node.has_len && !c.check_elements_ref_containers_initialized(node.elem_type) {
-			c.warn('arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`)',
-				node.pos)
-		}
 		// `&Struct{} check
 		if node.has_len {
-			c.check_elements_ref_fields_initialized(node.elem_type, node.pos)
+			c.check_elements_ref_fields_initialized(unwrap_elem_type, node.pos)
 		}
 		return node.typ
 	}
 
 	if node.is_fixed {
-		c.ensure_sumtype_array_has_default_value(node)
 		c.ensure_type_exists(node.elem_type, node.elem_type_pos)
-		if !c.is_builtin_mod && !c.check_elements_ref_containers_initialized(node.elem_type) {
-			c.warn('fixed arrays of references need to be initialized right away (unless inside `unsafe`)',
-				node.pos)
+		if !c.is_builtin_mod {
+			c.check_elements_initialized(unwrap_elem_type) or {
+				c.warn('fixed ${err.msg()} (unless inside `unsafe`)', node.pos)
+			}
 		}
-		c.check_elements_ref_fields_initialized(node.elem_type, node.pos)
+		c.check_elements_ref_fields_initialized(unwrap_elem_type, node.pos)
 	}
 	// `a = []`
 	if node.exprs.len == 0 {
@@ -351,13 +346,6 @@ fn (mut c Checker) check_array_init_para_type(para string, mut expr ast.Expr, po
 	}
 }
 
-fn (mut c Checker) ensure_sumtype_array_has_default_value(node ast.ArrayInit) {
-	sym := c.table.sym(node.elem_type)
-	if sym.kind == .sum_type && !node.has_init {
-		c.error('cannot initialize sum type array without default value', node.pos)
-	}
-}
-
 fn (mut c Checker) map_init(mut node ast.MapInit) ast.Type {
 	// `map = {}`
 	if node.keys.len == 0 && node.vals.len == 0 && node.typ == 0 {
@@ -574,42 +562,46 @@ fn (mut c Checker) do_check_elements_ref_fields_initialized(sym &ast.TypeSymbol,
 	}
 }
 
-// check the element, and its children for ref uninitialized containers
-fn (mut c Checker) check_elements_ref_containers_initialized(typ ast.Type) bool {
+const err_ref_uninitialized = error('arrays of references need to be initialized right away')
+const err_interface_uninitialized = error('arrays of interfaces need to be initialized right away')
+const err_sumtype_uninitialized = error('arrays of sumtypes need to be initialized right away')
+
+// check the element, and its children for `ref/interface/sumtype` initialized
+fn (mut c Checker) check_elements_initialized(typ ast.Type) ! {
 	if typ == 0 || c.inside_unsafe {
-		return true
+		return
 	}
 	if typ.is_any_kind_of_pointer() {
-		return false
+		return checker.err_ref_uninitialized
 	}
 	sym := c.table.sym(typ)
+	if sym.kind == .interface_ {
+		return checker.err_interface_uninitialized
+	} else if sym.kind == .sum_type {
+		return checker.err_sumtype_uninitialized
+	}
+
 	match sym.info {
 		ast.Array {
 			elem_type := sym.info.elem_type
-			if elem_type.is_any_kind_of_pointer() {
-				return false
-			}
-			return c.check_elements_ref_containers_initialized(elem_type)
+			return c.check_elements_initialized(elem_type)
 		}
 		ast.ArrayFixed {
 			elem_type := sym.info.elem_type
-			if elem_type.is_any_kind_of_pointer() && !c.is_builtin_mod {
-				return false
+			if !c.is_builtin_mod {
+				return c.check_elements_initialized(elem_type)
 			}
-			return c.check_elements_ref_containers_initialized(elem_type)
 		}
 		ast.Map {
 			value_type := sym.info.value_type
-			if value_type.is_any_kind_of_pointer() && !c.is_builtin_mod {
-				return false
+			if !c.is_builtin_mod {
+				return c.check_elements_initialized(value_type)
 			}
-			return c.check_elements_ref_containers_initialized(value_type)
 		}
 		ast.Alias {
 			parent_type := sym.info.parent_type
-			return c.check_elements_ref_containers_initialized(parent_type)
+			return c.check_elements_initialized(parent_type)
 		}
 		else {}
 	}
-	return true
 }

vlib/v/checker/tests/array_init_without_init_value_err.out

@@ -0,0 +1,70 @@
+vlib/v/checker/tests/array_init_without_init_value_err.vv:5:7: warning: arrays of sumtypes need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+    3 | 
+    4 | fn main_sum_type() {
+    5 |     a := []Foo{len: 10}
+      |          ~~~~~~
+    6 |     println(a)
+    7 |     fixed_a := [10]Foo{}
+vlib/v/checker/tests/array_init_without_init_value_err.vv:7:13: warning: fixed arrays of sumtypes need to be initialized right away (unless inside `unsafe`)
+    5 |     a := []Foo{len: 10}
+    6 |     println(a)
+    7 |     fixed_a := [10]Foo{}
+      |                ~~~~~~~~~
+    8 |     println(fixed_a)
+    9 | }
+vlib/v/checker/tests/array_init_without_init_value_err.vv:20:11: warning: arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   18 | // test references uninitialized.
+   19 | fn main_ref() {
+   20 |     println(*[]&int{len: 1}[0])
+      |              ~~~~~~~
+   21 |     println([1]&int{})
+   22 |     _ = [][1]&int{len: 1}[0][0]
+vlib/v/checker/tests/array_init_without_init_value_err.vv:21:10: warning: fixed arrays of references need to be initialized right away (unless inside `unsafe`)
+   19 | fn main_ref() {
+   20 |     println(*[]&int{len: 1}[0])
+   21 |     println([1]&int{})
+      |             ~~~~~~~~~
+   22 |     _ = [][1]&int{len: 1}[0][0]
+   23 |     _ = []map[int]&int{len: 1}
+vlib/v/checker/tests/array_init_without_init_value_err.vv:22:6: warning: arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   20 |     println(*[]&int{len: 1}[0])
+   21 |     println([1]&int{})
+   22 |     _ = [][1]&int{len: 1}[0][0]
+      |         ~~~~~~~~~~
+   23 |     _ = []map[int]&int{len: 1}
+   24 | }
+vlib/v/checker/tests/array_init_without_init_value_err.vv:23:6: warning: arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   21 |     println([1]&int{})
+   22 |     _ = [][1]&int{len: 1}[0][0]
+   23 |     _ = []map[int]&int{len: 1}
+      |         ~~~~~~~~~~~~~~~
+   24 | }
+   25 |
+vlib/v/checker/tests/array_init_without_init_value_err.vv:40:22: warning: arrays of interfaces need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   38 | 
+   39 | fn main_interface() {
+   40 |     mut parsed_lines := []MObject{len: 9}
+      |                         ~~~~~~~~~~
+   41 |     println(parsed_lines)
+   42 | }
+vlib/v/checker/tests/array_init_without_init_value_err.vv:12:7: warning: arrays of sumtypes need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   10 | 
+   11 | fn main_sum_type_2[T]() {
+   12 |     a := []T{len: 10}
+      |          ~~~~
+   13 |     println(a)
+   14 |     fixed_a := [10]T{}
+vlib/v/checker/tests/array_init_without_init_value_err.vv:14:13: warning: fixed arrays of sumtypes need to be initialized right away (unless inside `unsafe`)
+   12 |     a := []T{len: 10}
+   13 |     println(a)
+   14 |     fixed_a := [10]T{}
+      |                ~~~~~~~
+   15 |     println(fixed_a)
+   16 | }
+vlib/v/checker/tests/array_init_without_init_value_err.vv:45:22: warning: arrays of interfaces need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
+   43 | 
+   44 | fn main_interface_2[T]() {
+   45 |     mut parsed_lines := []T{len: 9}
+      |                         ~~~~
+   46 |     println(parsed_lines)
+   47 | }

vlib/v/checker/tests/array_init_without_init_value_err.vv

@@ -0,0 +1,57 @@
+// test sum_types uninitialized.
+type Foo = int | string
+
+fn main_sum_type() {
+	a := []Foo{len: 10}
+	println(a)
+	fixed_a := [10]Foo{}
+	println(fixed_a)
+}
+
+fn main_sum_type_2[T]() {
+	a := []T{len: 10}
+	println(a)
+	fixed_a := [10]T{}
+	println(fixed_a)
+}
+
+// test references uninitialized.
+fn main_ref() {
+	println(*[]&int{len: 1}[0])
+	println([1]&int{})
+	_ = [][1]&int{len: 1}[0][0]
+	_ = []map[int]&int{len: 1}
+}
+
+// test interfaces uninitialized.
+interface MObject {
+	give_string() string
+}
+
+struct LeStruct {
+	le_string string
+}
+
+fn (a LeStruct) give_string() string {
+	return 'V'
+}
+
+fn main_interface() {
+	mut parsed_lines := []MObject{len: 9}
+	println(parsed_lines)
+}
+
+fn main_interface_2[T]() {
+	mut parsed_lines := []T{len: 9}
+	println(parsed_lines)
+}
+
+fn main() {
+	main_sum_type()
+	main_sum_type_2[Foo]()
+
+	main_ref()
+
+	main_interface()
+	main_interface_2[MObject]()
+}

vlib/v/checker/tests/shared_element_lock.out

@@ -1,4 +1,4 @@
-vlib/v/checker/tests/shared_element_lock.vv:43:11: warning: arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`)
+vlib/v/checker/tests/shared_element_lock.vv:43:11: warning: arrays of references need to be initialized right away, therefore `len:` cannot be used (unless inside `unsafe`, or if you also use `init:`)
    41 |     shared g := Pro{}
    42 |     g.pers.age = 42
    43 |     mut h := []shared Pro{len: 3}