# V2001 type_mismatch

URL: /docs/errors/V2001
Markdown: /docs/errors/V2001.md

> An expression has a different type from the one its context requires.

An error from the `type` phase. `sakura explain V2001` prints this explanation offline.

An expression has a different type from the one its context requires. `expected` and `actual`
carry both types.

Wrong:

```sakura
fn double(x: Int) -> Int { x * 2.0 }
```

Fixed:

```sakura
fn double(x: Int) -> Int { x * 2 }
```

## Wrong program [#wrong-program]

[`compiler/tests/ui/V2001_type_mismatch.sakura`](https://github.com/icantcodefyi/sakuralang/blob/master/compiler/tests/ui/V2001_type_mismatch.sakura), which the compiler's ui suite runs through `sakura check`:

```sakura
fn age() -> Int { "forty" }
```

`sakura check --json` reports this record (pretty-printed; `$DIR` is the fixture's directory):

```json
{
  "schema_version": "1.0",
  "kind": "diagnostic",
  "id": "d:c2099b6a910033c7",
  "code": "V2001",
  "severity": "error",
  "phase": "type",
  "message": "expected `Int`, found `String`",
  "snapshot": "sha256:$SNAPSHOT",
  "symbol_id": "main::V2001_type_mismatch::age",
  "spans": [
    {
      "uri": "file://$DIR/V2001_type_mismatch.sakura",
      "content_hash": "sha256:ba191e33c0daecd6ab8441edc074708a7abbc21c3a46cbcf5927c1a9a99784d0",
      "start_byte": 52,
      "end_byte": 59,
      "role": "primary",
      "label": "this has type `String`"
    }
  ],
  "related_ids": [],
  "expected": {
    "render": "Int"
  },
  "actual": {
    "render": "String"
  },
  "obligation": null,
  "counterexample": null,
  "explanation_uri": "sakura://explain/V2001",
  "fixes": []
}
```

## Fixed program [#fixed-program]

[`compiler/tests/ui/V2001_type_mismatch.fixed.sakura`](https://github.com/icantcodefyi/sakuralang/blob/master/compiler/tests/ui/V2001_type_mismatch.fixed.sakura), which `sakura check` accepts with no diagnostics:

```sakura
fn age() -> Int { 40 }
```