checker: check fixed array index when it's a literal (#8831)

vlib/v/checker/checker.v

@@ -5149,13 +5149,13 @@ pub fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) table.Type {
 	return right_type
 }
 
-fn (mut c Checker) check_index(typ_sym &table.TypeSymbol, index ast.Expr, index_type table.Type, pos token.Position) {
+fn (mut c Checker) check_index(typ_sym &table.TypeSymbol, index ast.Expr, index_type table.Type, pos token.Position, range_index bool) {
 	index_type_sym := c.table.get_type_symbol(index_type)
 	// println('index expr left=$typ_sym.name $node.pos.line_nr')
 	// if typ_sym.kind == .array && (!(table.type_idx(index_type) in table.number_type_idxs) &&
 	// index_type_sym.kind != .enum_) {
 	if typ_sym.kind in [.array, .array_fixed, .string, .ustring] {
-		if !(index_type.is_number() || index_type_sym.kind == .enum_) {
+		if !(index_type.is_int() || index_type_sym.kind == .enum_) {
 			type_str := if typ_sym.kind in [.string, .ustring] {
 				'non-integer string index `$index_type_sym.name`'
 			} else {
@@ -5164,8 +5164,14 @@ fn (mut c Checker) check_index(typ_sym &table.TypeSymbol, index ast.Expr, index_
 			c.error('$type_str', pos)
 		}
 		if index is ast.IntegerLiteral {
-			if index.val.starts_with('-') {
+			if index.val[0] == `-` {
-				c.error('invalid index `$index.val` (index must be non-negative)', index.pos)
+				c.error('negative index `$index.val`', index.pos)
+			} else if typ_sym.kind == .array_fixed {
+				i := index.val.int()
+				info := typ_sym.info as table.ArrayFixed
+				if (!range_index && i >= info.size) || (range_index && i > info.size) {
+					c.error('index out of range (index: $i, len: $info.size)', index.pos)
+				}
 			}
 		}
 		if index_type.has_flag(.optional) {
@@ -5220,11 +5226,11 @@ pub fn (mut c Checker) index_expr(mut node ast.IndexExpr) table.Type {
 	if mut node.index is ast.RangeExpr { // [1..2]
 		if node.index.has_low {
 			index_type := c.expr(node.index.low)
-			c.check_index(typ_sym, node.index.low, index_type, node.pos)
+			c.check_index(typ_sym, node.index.low, index_type, node.pos, true)
 		}
 		if node.index.has_high {
 			index_type := c.expr(node.index.high)
-			c.check_index(typ_sym, node.index.high, index_type, node.pos)
+			c.check_index(typ_sym, node.index.high, index_type, node.pos, true)
 		}
 		// array[1..2] => array
 		// fixed_array[1..2] => array
@@ -5244,7 +5250,7 @@ pub fn (mut c Checker) index_expr(mut node ast.IndexExpr) table.Type {
 				c.error('invalid key: $err', node.pos)
 			}
 		} else {
-			c.check_index(typ_sym, node.index, index_type, node.pos)
+			c.check_index(typ_sym, node.index, index_type, node.pos, false)
 		}
 		value_type := c.table.value_type(typ)
 		if value_type != table.void_type {

vlib/v/checker/tests/array_index.out

@@ -0,0 +1,34 @@
+vlib/v/checker/tests/array_index.vv:3:7: error: non-integer index `float literal` (array type `[2]int`)
+    1 | fn fixed() {
+    2 |     a := [1,2]!
+    3 |     _ = a[0.2]
+      |          ~~~~~
+    4 |     _ = a[1] // OK
+    5 |     _ = a[-1]
+vlib/v/checker/tests/array_index.vv:5:8: error: negative index `-1`
+    3 |     _ = a[0.2]
+    4 |     _ = a[1] // OK
+    5 |     _ = a[-1]
+      |           ~~
+    6 |     _ = a[2]
+    7 |     _ = a[1..2] // OK
+vlib/v/checker/tests/array_index.vv:6:8: error: index out of range (index: 2, len: 2)
+    4 |     _ = a[1] // OK
+    5 |     _ = a[-1]
+    6 |     _ = a[2]
+      |           ^
+    7 |     _ = a[1..2] // OK
+    8 |     _ = a[2..2] // empty, OK
+vlib/v/checker/tests/array_index.vv:9:11: error: index out of range (index: 3, len: 2)
+    7 |     _ = a[1..2] // OK
+    8 |     _ = a[2..2] // empty, OK
+    9 |     _ = a[1..3]
+      |              ^
+   10 |     _ = a[3..3]
+   11 | }
+vlib/v/checker/tests/array_index.vv:10:8: error: index out of range (index: 3, len: 2)
+    8 |     _ = a[2..2] // empty, OK
+    9 |     _ = a[1..3]
+   10 |     _ = a[3..3]
+      |           ^
+   11 | }

vlib/v/checker/tests/array_index.vv

@@ -0,0 +1,11 @@
+fn fixed() {
+	a := [1,2]!
+	_ = a[0.2]
+	_ = a[1] // OK
+	_ = a[-1]
+	_ = a[2]
+	_ = a[1..2] // OK
+	_ = a[2..2] // empty, OK
+	_ = a[1..3]
+	_ = a[3..3]
+}

vlib/v/checker/tests/index_expr.out

@@ -3,16 +3,16 @@ vlib/v/checker/tests/index_expr.vv:3:7: error: type `int` does not support index
     2 |     v := 4
     3 |     _ = v[0]
       |          ~~~
-    4 |
+    4 | 
     5 |     a := [2]
 vlib/v/checker/tests/index_expr.vv:6:7: error: non-integer index `[]int` (array type `[]int`)
-    4 |
+    4 | 
     5 |     a := [2]
     6 |     _ = a[a]
       |          ~~~
     7 |     _ = a[-1]
     8 | }
-vlib/v/checker/tests/index_expr.vv:7:8: error: invalid index `-1` (index must be non-negative)
+vlib/v/checker/tests/index_expr.vv:7:8: error: negative index `-1`
     5 |     a := [2]
     6 |     _ = a[a]
     7 |     _ = a[-1]
@@ -31,10 +31,10 @@ vlib/v/checker/tests/index_expr.vv:13:7: error: type `int` does not support inde
    12 |     _ = v[1..]
    13 |     _ = v[..1]
       |          ~~~~~
-   14 |
+   14 | 
    15 |     a := [2]
 vlib/v/checker/tests/index_expr.vv:16:7: error: non-integer index `[]int` (array type `[]int`)
-   14 |
+   14 | 
    15 |     a := [2]
    16 |     _ = a[a..]
       |          ~~~~~
@@ -47,21 +47,21 @@ vlib/v/checker/tests/index_expr.vv:17:7: error: non-integer index `[]int` (array
       |          ~~~~~
    18 |     _ = a[-1..]
    19 |     _ = a[..-1]
-vlib/v/checker/tests/index_expr.vv:18:8: error: invalid index `-1` (index must be non-negative)
+vlib/v/checker/tests/index_expr.vv:18:8: error: negative index `-1`
    16 |     _ = a[a..]
    17 |     _ = a[..a]
    18 |     _ = a[-1..]
       |           ~~
    19 |     _ = a[..-1]
    20 |     _ = a[-1..-2]
-vlib/v/checker/tests/index_expr.vv:19:10: error: invalid index `-1` (index must be non-negative)
+vlib/v/checker/tests/index_expr.vv:19:10: error: negative index `-1`
    17 |     _ = a[..a]
    18 |     _ = a[-1..]
    19 |     _ = a[..-1]
       |             ~~
    20 |     _ = a[-1..-2]
    21 | }
-vlib/v/checker/tests/index_expr.vv:20:8: error: invalid index `-1` (index must be non-negative)
+vlib/v/checker/tests/index_expr.vv:20:8: error: negative index `-1`
    18 |     _ = a[-1..]
    19 |     _ = a[..-1]
    20 |     _ = a[-1..-2]