# Expressions

## OR

```py
def foo() -> str:
    pass

reveal_type(True or False)  # revealed: Literal[True]
reveal_type("x" or "y" or "z")  # revealed: Literal["x"]
reveal_type("" or "y" or "z")  # revealed: Literal["y"]
reveal_type(False or "z")  # revealed: Literal["z"]
reveal_type(False or True)  # revealed: Literal[True]
reveal_type(False or False)  # revealed: Literal[False]
reveal_type(foo() or False)  # revealed: str | Literal[False]
reveal_type(foo() or True)  # revealed: str | Literal[True]
```

## AND

```py
def foo() -> str:
    pass

reveal_type(True and False)  # revealed: Literal[False]
reveal_type(False and True)  # revealed: Literal[False]
reveal_type(foo() and False)  # revealed: str | Literal[False]
reveal_type(foo() and True)  # revealed: str | Literal[True]
reveal_type("x" and "y" and "z")  # revealed: Literal["z"]
reveal_type("x" and "y" and "")  # revealed: Literal[""]
reveal_type("" and "y")  # revealed: Literal[""]
```

## Simple function calls to bool

```py
def returns_bool() -> bool:
    return True

if returns_bool():
    x = True
else:
    x = False

reveal_type(x)  # revealed: bool
```

## Complex

```py
def foo() -> str:
    pass

reveal_type("x" and "y" or "z")  # revealed: Literal["y"]
reveal_type("x" or "y" and "z")  # revealed: Literal["x"]
reveal_type("" and "y" or "z")  # revealed: Literal["z"]
reveal_type("" or "y" and "z")  # revealed: Literal["z"]
reveal_type("x" and "y" or "")  # revealed: Literal["y"]
reveal_type("x" or "y" and "")  # revealed: Literal["x"]
```

## `bool()` function

## Evaluates to builtin

```py path=a.py
redefined_builtin_bool = bool

def my_bool(x) -> bool:
    return True
```

```py
from a import redefined_builtin_bool, my_bool

reveal_type(redefined_builtin_bool(0))  # revealed: Literal[False]
reveal_type(my_bool(0))  # revealed: bool
```

## Truthy values

```py
reveal_type(bool(1))  # revealed: Literal[True]
reveal_type(bool((0,)))  # revealed: Literal[True]
reveal_type(bool("NON EMPTY"))  # revealed: Literal[True]
reveal_type(bool(True))  # revealed: Literal[True]

def foo(): ...

reveal_type(bool(foo))  # revealed: Literal[True]
```

## Falsy values

```py
reveal_type(bool(0))  # revealed: Literal[False]
reveal_type(bool(()))  # revealed: Literal[False]
reveal_type(bool(None))  # revealed: Literal[False]
reveal_type(bool(""))  # revealed: Literal[False]
reveal_type(bool(False))  # revealed: Literal[False]
reveal_type(bool())  # revealed: Literal[False]
```

## Ambiguous values

```py
reveal_type(bool([]))  # revealed: bool
reveal_type(bool({}))  # revealed: bool
reveal_type(bool(set()))  # revealed: bool
```