checker: check array init's element type

vlib/v/ast/ast.v

@@ -657,6 +657,7 @@ pub:
 pub struct ArrayInit {
 pub:
 	pos             token.Position
+	elem_type_pos	token.Position
 	exprs           []Expr
 	is_fixed        bool
 	has_val         bool

vlib/v/checker/checker.v

@@ -1334,6 +1334,10 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 				}
 			}
 		}
+		sym := c.table.get_type_symbol(array_init.elem_type)
+		if sym.kind == .placeholder {
+			c.error('unknown type `$sym.name`', array_init.elem_type_pos)
+		}
 		return array_init.typ
 	}
 	// a = []

vlib/v/checker/tests/unknown_array_element_type.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/unknown_array_element_type.v:2:9: error: unknown type `abc`
+    1 | fn main() {
+    2 |     a := []abc{}
+      |            ~~~
+    3 |     println(a)
+    4 | }

vlib/v/checker/tests/unknown_array_element_type.vv

@@ -0,0 +1,4 @@
+fn main() {
+	a := []abc{}
+	println(a)
+}

vlib/v/parser/containers.v

@@ -14,6 +14,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 	// p.warn('array_init() exp=$p.expected_type')
 	mut array_type := table.void_type
 	mut elem_type := table.void_type
+	mut elem_type_pos := first_pos
 	mut exprs := []ast.Expr{}
 	mut is_fixed := false
 	mut has_val := false
@@ -24,6 +25,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 		p.next()
 		// []string
 		if p.tok.kind in [.name, .amp] && p.tok.line_nr == line_nr {
+			elem_type_pos = p.tok.position()
 			elem_type = p.parse_type()
 			// this is set here becasue its a known type, others could be the
 			// result of expr so we do those in checker
@@ -118,6 +120,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 		typ: array_type
 		exprs: exprs
 		pos: pos
+		elem_type_pos: elem_type_pos
 		has_len: has_len
 		len_expr: len_expr
 		has_cap: has_cap