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Add named expressions / assignment expressions #1638

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13 changes: 13 additions & 0 deletions compiler/src/compile.rs
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Expand Up @@ -1565,6 +1565,17 @@ impl<O: OutputStream> Compiler<O> {
Ok(())
}

fn compile_named_expression(
&mut self,
target: &ast::Expression,
value: &ast::Expression,
) -> Result<(), CompileError> {

// evaluate value
// store into target
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@dralley dralley Dec 19, 2019 •
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TODO -- still having trouble w/ parsing

Ok(())
}

fn compile_expression(&mut self, expression: &ast::Expression) -> Result<(), CompileError> {
trace!("Compiling {:?}", expression);
self.set_source_location(&expression.location);
Expand All @@ -1577,6 +1588,7 @@ impl<O: OutputStream> Compiler<O> {
keywords,
} => self.compile_call(function, args, keywords)?,
BoolOp { op, values } => self.compile_bool_op(op, values)?,
NamedExpression { target, value} => self.compile_named_expression(target, value)?,
Binop { a, op, b } => {
self.compile_expression(a)?;
self.compile_expression(b)?;
Expand Down Expand Up @@ -1913,6 +1925,7 @@ impl<O: OutputStream> Compiler<O> {
Ok(has_stars)
}


fn compile_comprehension(
&mut self,
kind: &ast::ComprehensionKind,
Expand Down
4 changes: 4 additions & 0 deletions compiler/src/symboltable.rs
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Expand Up @@ -547,6 +547,10 @@ impl SymbolTableBuilder {
self.scan_expression(a, context)?;
self.scan_expression(b, context)?;
}
NamedExpression {target, value} => {
self.scan_expression(target, &ExpressionContext::Store)?;
self.scan_expression(value, &ExpressionContext::Load)?;
},
BoolOp { values, .. } => {
self.scan_expressions(values, context)?;
}
Expand Down
9 changes: 8 additions & 1 deletion parser/src/ast.rs
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Expand Up @@ -186,6 +186,12 @@ pub enum ExpressionType {
values: Vec<Expression>,
},

/// A named expression aka. assignment expression aka. "Walrus operator"
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The fact that the PEP and the implementation use different terminology is somewhat irritating.

NamedExpression {
target: Box<Expression>,
value: Box<Expression>,
},

/// A binary operation on two operands.
Binop {
a: Box<Expression>,
Expand Down Expand Up @@ -330,6 +336,7 @@ impl Expression {

match &self.node {
BoolOp { .. } | Binop { .. } | Unop { .. } => "operator",
NamedExpression { .. } => "named expression",
Subscript { .. } => "subscript",
Await { .. } => "await expression",
Yield { .. } | YieldFrom { .. } => "yield expression",
Expand Down Expand Up @@ -359,7 +366,7 @@ impl Expression {
| String {
value: FormattedValue { .. },
} => "f-string expression",
Identifier { .. } => "named expression",
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@dralley dralley Dec 19, 2019 •
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This was a typo, right? Or maybe it predates "named expressions" becoming an actual thing in Python?

Identifier { .. } => "identifier",
Lambda { .. } => "lambda",
IfExpression { .. } => "conditional expression",
True | False | None => "keyword",
Expand Down
11 changes: 10 additions & 1 deletion parser/src/lexer.rs
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Expand Up @@ -1095,7 +1095,16 @@ where
self.nesting -= 1;
}
':' => {
self.eat_single_char(Tok::Colon);
let tok_start = self.get_pos();
self.next_char();
if let Some('=') = self.chr0 {
self.next_char();
let tok_end = self.get_pos();
self.emit((tok_start, Tok::ColonEqual, tok_end));
} else {
let tok_end = self.get_pos();
self.emit((tok_start, Tok::Colon, tok_end));
}
}
';' => {
self.eat_single_char(Tok::Semi);
Expand Down
9 changes: 9 additions & 0 deletions parser/src/python.lalrpop
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Expand Up @@ -787,6 +787,14 @@ MulOp: ast::Operator = {
"@" => ast::Operator::MatMult,
};

NamedExpression: ast::Expression = {
<e1:Expression> <location:@L> ":=" <e2:Expression> => ast::Expression {
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Please keep in mind here to check with this page: https://docs.python.org/3/reference/grammar.html?highlight=grammar

That's the reference I used when making the rest of this file. Instead of <e1:Expression> you might want to go for <e1:Test>.

location,
node: ast::ExpressionType::NamedExpression { target: Box::new(e1), value: Box::new(e2) }
},
NamedExpression,
};
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Probably this is wrong. I'm getting LalrpopError::UnrecognizedToken->ParseErrorType::UnrecognizedToken

>>>>> if any(len(longline := line) >= 100 for line in lines):
SyntaxError: 
if any(len(longline := line) >= 100 for line in lines):
                    ↑
                    Got unexpected token ':='

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It looks like you might want to use TestOrStarExpr, as that's what the assignment statement does:

RustPython/parser/src/python.lalrpop

Line 88 in ed37c61

<location:@L> <expression:TestOrStarExprList> <suffix:AssignSuffix*> => {

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It didn't work unfortunately. Might still be doing something wrong, idk. I'll take another shot after New Years and do some deeper digging.

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Please check with the grammar on this page: https://docs.python.org/3/reference/grammar.html?highlight=grammar that contains useful tips on what to modify.


Factor: ast::Expression = {
<location:@L> <op:UnOp> <e:Factor> => ast::Expression {
location,
Expand Down Expand Up @@ -1169,6 +1177,7 @@ extern {
"//=" => lexer::Tok::DoubleSlashEqual,
"==" => lexer::Tok::EqEqual,
"!=" => lexer::Tok::NotEqual,
":=" => lexer::Tok::ColonEqual,
"<" => lexer::Tok::Less,
"<=" => lexer::Tok::LessEqual,
">" => lexer::Tok::Greater,
Expand Down
2 changes: 2 additions & 0 deletions parser/src/token.rs
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Expand Up @@ -59,6 +59,7 @@ pub enum Tok {
CircumflexEqual, // '^='
LeftShiftEqual,
RightShiftEqual,
ColonEqual,
DoubleSlash, // '//'
DoubleSlashEqual,
At,
Expand Down Expand Up @@ -181,6 +182,7 @@ impl fmt::Display for Tok {
CircumflexEqual => f.write_str("'^='"),
LeftShiftEqual => f.write_str("'<<='"),
RightShiftEqual => f.write_str("'>>='"),
ColonEqual => f.write_str("':='"),
DoubleSlash => f.write_str("'//'"),
DoubleSlashEqual => f.write_str("'//='"),
At => f.write_str("'@'"),
Expand Down
3 changes: 3 additions & 0 deletions vm/src/exceptions.rs
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Expand Up @@ -404,6 +404,7 @@ pub struct ExceptionZoo {
pub syntax_error: PyClassRef,
pub indentation_error: PyClassRef,
pub tab_error: PyClassRef,
pub target_scope_error: PyClassRef,
pub system_error: PyClassRef,
pub type_error: PyClassRef,
pub value_error: PyClassRef,
Expand Down Expand Up @@ -473,6 +474,7 @@ impl ExceptionZoo {
let eof_error = create_type("EOFError", &type_type, &exception_type);
let indentation_error = create_type("IndentationError", &type_type, &syntax_error);
let tab_error = create_type("TabError", &type_type, &indentation_error);
let target_scope_error = create_type("TargetScopeError", &type_type, &syntax_error);
let unicode_error = create_type("UnicodeError", &type_type, &value_error);
let unicode_decode_error = create_type("UnicodeDecodeError", &type_type, &unicode_error);
let unicode_encode_error = create_type("UnicodeEncodeError", &type_type, &unicode_error);
Expand Down Expand Up @@ -571,6 +573,7 @@ impl ExceptionZoo {
keyboard_interrupt,
generator_exit,
system_exit,
target_scope_error,
}
}
}
Expand Down
6 changes: 6 additions & 0 deletions vm/src/stdlib/ast.rs
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Expand Up @@ -328,6 +328,12 @@ fn expression_to_ast(vm: &VirtualMachine, expression: &ast::Expression) -> PyRes
args => expressions_to_ast(vm, args)?,
keywords => map_ast(keyword_to_ast, vm, keywords)?,
}),
NamedExpression {target, value} => {
node!(vm, NamedExpression, {
target => expression_to_ast(vm, target)?,
value => expression_to_ast(vm, value)?,
})
},
Binop { a, op, b } => {
// Operator:
node!(vm, BinOp, {
Expand Down