Add tests

Author: GearsDatapacks

compiler-core/src/type_/tests/errors.rs

@@ -3109,3 +3109,14 @@ fn negative_size_pattern() {
 fn zero_size_pattern() {
     assert_error!("let assert <<1:size(0)>> = <<>>");
 }
+
+// https://github.com/gleam-lang/gleam/issues/3253
+#[test]
+fn bit_array_using_pattern_variables() {
+    assert_error!("let assert #(a, <<b:size(a)>>) = #(2, <<2:2>>)");
+}
+
+#[test]
+fn bit_array_using_pattern_variables_from_other_bit_array() {
+    assert_error!("let assert #(<<a>>, <<b:size(a)>>) = #(<<2>>, <<2:2>>)");
+}

compiler-core/src/type_/tests/snapshots/gleam_core__type___tests__errors__bit_array_using_pattern_variables.snap

@@ -0,0 +1,15 @@
+---
+source: compiler-core/src/type_/tests/errors.rs
+expression: "let assert #(a, <<b:size(a)>>) = #(2, <<2:2>>)"
+---
+----- SOURCE CODE
+let assert #(a, <<b:size(a)>>) = #(2, <<2:2>>)
+
+----- ERROR
+error: Unknown variable
+  ┌─ /src/one/two.gleam:1:26
+  │
+1 │ let assert #(a, <<b:size(a)>>) = #(2, <<2:2>>)
+  │                          ^
+
+The name `a` is not in scope here.

compiler-core/src/type_/tests/snapshots/gleam_core__type___tests__errors__bit_array_using_pattern_variables_from_other_bit_array.snap

@@ -0,0 +1,15 @@
+---
+source: compiler-core/src/type_/tests/errors.rs
+expression: "let assert #(<<a>>, <<b:size(a)>>) = #(<<2>>, <<2:2>>)"
+---
+----- SOURCE CODE
+let assert #(<<a>>, <<b:size(a)>>) = #(<<2>>, <<2:2>>)
+
+----- ERROR
+error: Unknown variable
+  ┌─ /src/one/two.gleam:1:30
+  │
+1 │ let assert #(<<a>>, <<b:size(a)>>) = #(<<2>>, <<2:2>>)
+  │                              ^
+
+The name `a` is not in scope here.