ruff/crates/red_knot_python_semantic/resources/mdtest/invalid_syntax.md

Syntax errors

Test cases to ensure that red knot does not panic if there are syntax errors in the source code.

The parser cannot recover from certain syntax errors completely which is why the number of syntax errors could be more than expected in the following examples. For instance, if there's a keyword (like for) in the middle of another statement (like function definition), then it's more likely that the rest of the tokens are going to be part of the for statement and not the function definition. But, it's not necessary that the remaining tokens are valid in the context of a for statement.

Keyword as identifiers

When keywords are used as identifiers, the parser recovers from this syntax error by emitting an error and including the text value of the keyword to create the Identifier node.

Name expression

Assignment

# error: [invalid-syntax]
pass = 1

Type alias

# error: [invalid-syntax]
# error: [invalid-syntax]
type pass = 1

Function definition

# error: [invalid-syntax]
# error: [invalid-syntax]
# error: [invalid-syntax]
# error: [invalid-syntax]
# error: [invalid-syntax]
def True(for):
    # error: [invalid-syntax]
    # error: [invalid-syntax]
    pass

For

# error: [invalid-syntax]
# error: [invalid-syntax]
# error: [unresolved-reference] "Name `pass` used when not defined"
for while in pass:
    pass

While

# error: [invalid-syntax]
# error: [unresolved-reference] "Name `in` used when not defined"
while in:
    pass

Match

# error: [invalid-syntax]
# error: [invalid-syntax]
# error: [unresolved-reference] "Name `match` used when not defined"
match while:
    # error: [invalid-syntax]
    # error: [invalid-syntax]
    # error: [invalid-syntax]
    # error: [unresolved-reference] "Name `case` used when not defined"
    case in:
        # error: [invalid-syntax]
        # error: [invalid-syntax]
        pass

Attribute expression

# TODO: Check when support for attribute expressions is added

# error: [invalid-syntax]
# error: [unresolved-reference] "Name `foo` used when not defined"
for x in foo.pass:
    pass