c2c10e2bc0
This commit replaces the previous naive coloring system with a coloring
system that is more aligned with the parser.
The main benefit of this change is that it allows us to use parsing
rules to decide how to color tokens.
For example, consider the following syntax:
```
$ ps | where cpu > 10
```
Ideally, we could color `cpu` like a column name and not a string,
because `cpu > 10` is a shorthand block syntax that expands to
`{ $it.cpu > 10 }`.
The way that we know that it's a shorthand block is that the `where`
command declares that its first parameter is a `SyntaxShape::Block`,
which allows the shorthand block form.
In order to accomplish this, we need to color the tokens in a way that
corresponds to their expanded semantics, which means that high-fidelity
coloring requires expansion.
This commit adds a `ColorSyntax` trait that corresponds to the
`ExpandExpression` trait. The semantics are fairly similar, with a few
differences.
First `ExpandExpression` consumes N tokens and returns a single
`hir::Expression`. `ColorSyntax` consumes N tokens and writes M
`FlatShape` tokens to the output.
Concretely, for syntax like `[1 2 3]`
- `ExpandExpression` takes a single token node and produces a single
`hir::Expression`
- `ColorSyntax` takes the same token node and emits 7 `FlatShape`s
(open delimiter, int, whitespace, int, whitespace, int, close
delimiter)
Second, `ColorSyntax` is more willing to plow through failures than
`ExpandExpression`.
In particular, consider syntax like
```
$ ps | where cpu >
```
In this case
- `ExpandExpression` will see that the `where` command is expecting a
block, see that it's not a literal block and try to parse it as a
shorthand block. It will successfully find a member followed by an
infix operator, but not a following expression. That means that the
entire pipeline part fails to parse and is a syntax error.
- `ColorSyntax` will also try to parse it as a shorthand block and
ultimately fail, but it will fall back to "backoff coloring mode",
which parsing any unidentified tokens in an unfallible, simple way. In
this case, `cpu` will color as a string and `>` will color as an
operator.
Finally, it's very important that coloring a pipeline infallibly colors
the entire string, doesn't fail, and doesn't get stuck in an infinite
loop.
In order to accomplish this, this PR separates `ColorSyntax`, which is
infallible from `FallibleColorSyntax`, which might fail. This allows the
type system to let us know if our coloring rules bottom out at at an
infallible rule.
It's not perfect: it's still possible for the coloring process to get
stuck or consume tokens non-atomically. I intend to reduce the
opportunity for those problems in a future commit. In the meantime, the
current system catches a number of mistakes (like trying to use a
fallible coloring rule in a loop without thinking about the possibility
that it will never terminate).
331 lines
10 KiB
Rust
331 lines
10 KiB
Rust
use crate::errors::ShellError;
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use crate::parser::{
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hir,
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hir::syntax_shape::{
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color_fallible_syntax, color_syntax_with, continue_expression, expand_expr, expand_syntax,
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DelimitedShape, ExpandContext, ExpandExpression, ExpressionContinuationShape,
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ExpressionListShape, FallibleColorSyntax, FlatShape, MemberShape, PathTailShape,
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VariablePathShape,
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},
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hir::tokens_iterator::TokensIterator,
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parse::token_tree::Delimiter,
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RawToken, TokenNode,
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};
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use crate::{Tag, Tagged, TaggedItem};
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#[derive(Debug, Copy, Clone)]
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pub struct AnyBlockShape;
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impl FallibleColorSyntax for AnyBlockShape {
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type Info = ();
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type Input = ();
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fn color_syntax<'a, 'b>(
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&self,
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_input: &(),
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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shapes: &mut Vec<Tagged<FlatShape>>,
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) -> Result<(), ShellError> {
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let block = token_nodes.peek_non_ws().not_eof("block");
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let block = match block {
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Err(_) => return Ok(()),
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Ok(block) => block,
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};
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// is it just a block?
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let block = block.node.as_block();
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match block {
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// If so, color it as a block
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Some((children, tags)) => {
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let mut token_nodes = TokensIterator::new(children.item, context.tag, false);
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color_syntax_with(
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&DelimitedShape,
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&(Delimiter::Brace, tags.0, tags.1),
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&mut token_nodes,
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context,
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shapes,
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);
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return Ok(());
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}
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_ => {}
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}
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// Otherwise, look for a shorthand block. If none found, fail
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color_fallible_syntax(&ShorthandBlock, token_nodes, context, shapes)
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}
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}
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impl ExpandExpression for AnyBlockShape {
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fn expand_expr<'a, 'b>(
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&self,
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token_nodes: &mut TokensIterator<'_>,
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context: &ExpandContext,
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) -> Result<hir::Expression, ShellError> {
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let block = token_nodes.peek_non_ws().not_eof("block")?;
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// is it just a block?
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let block = block.node.as_block();
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match block {
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Some((block, _tags)) => {
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let mut iterator = TokensIterator::new(&block.item, context.tag, false);
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let exprs = expand_syntax(&ExpressionListShape, &mut iterator, context)?;
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return Ok(hir::RawExpression::Block(exprs).tagged(block.tag));
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}
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_ => {}
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}
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expand_syntax(&ShorthandBlock, token_nodes, context)
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}
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}
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#[derive(Debug, Copy, Clone)]
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pub struct ShorthandBlock;
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impl FallibleColorSyntax for ShorthandBlock {
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type Info = ();
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type Input = ();
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fn color_syntax<'a, 'b>(
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&self,
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_input: &(),
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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shapes: &mut Vec<Tagged<FlatShape>>,
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) -> Result<(), ShellError> {
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// Try to find a shorthand head. If none found, fail
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color_fallible_syntax(&ShorthandPath, token_nodes, context, shapes)?;
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loop {
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// Check to see whether there's any continuation after the head expression
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let result =
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color_fallible_syntax(&ExpressionContinuationShape, token_nodes, context, shapes);
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match result {
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// if no continuation was found, we're done
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Err(_) => break,
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// if a continuation was found, look for another one
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Ok(_) => continue,
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}
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}
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Ok(())
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}
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}
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impl ExpandExpression for ShorthandBlock {
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fn expand_expr<'a, 'b>(
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&self,
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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) -> Result<hir::Expression, ShellError> {
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let path = expand_expr(&ShorthandPath, token_nodes, context)?;
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let start = path.tag;
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let expr = continue_expression(path, token_nodes, context)?;
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let end = expr.tag;
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let block = hir::RawExpression::Block(vec![expr]).tagged(start.until(end));
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Ok(block)
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}
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}
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/// A shorthand for `$it.foo."bar"`, used inside of a shorthand block
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#[derive(Debug, Copy, Clone)]
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pub struct ShorthandPath;
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impl FallibleColorSyntax for ShorthandPath {
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type Info = ();
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type Input = ();
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fn color_syntax<'a, 'b>(
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&self,
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_input: &(),
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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shapes: &mut Vec<Tagged<FlatShape>>,
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) -> Result<(), ShellError> {
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token_nodes.atomic(|token_nodes| {
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let variable = color_fallible_syntax(&VariablePathShape, token_nodes, context, shapes);
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match variable {
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Ok(_) => {
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// if it's a variable path, that's the head part
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return Ok(());
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}
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Err(_) => {
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// otherwise, we'll try to find a member path
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}
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}
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// look for a member (`<member>` -> `$it.<member>`)
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color_fallible_syntax(&MemberShape, token_nodes, context, shapes)?;
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// Now that we've synthesized the head, of the path, proceed to expand the tail of the path
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// like any other path.
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let tail = color_fallible_syntax(&PathTailShape, token_nodes, context, shapes);
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match tail {
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Ok(_) => {}
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Err(_) => {
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// It's ok if there's no path tail; a single member is sufficient
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}
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}
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Ok(())
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})
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}
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}
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impl ExpandExpression for ShorthandPath {
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fn expand_expr<'a, 'b>(
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&self,
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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) -> Result<hir::Expression, ShellError> {
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// if it's a variable path, that's the head part
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let path = expand_expr(&VariablePathShape, token_nodes, context);
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match path {
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Ok(path) => return Ok(path),
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Err(_) => {}
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}
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// Synthesize the head of the shorthand path (`<member>` -> `$it.<member>`)
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let mut head = expand_expr(&ShorthandHeadShape, token_nodes, context)?;
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// Now that we've synthesized the head, of the path, proceed to expand the tail of the path
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// like any other path.
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let tail = expand_syntax(&PathTailShape, token_nodes, context);
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match tail {
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Err(_) => return Ok(head),
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Ok((tail, _)) => {
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// For each member that `PathTailShape` expanded, join it onto the existing expression
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// to form a new path
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for member in tail {
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head = hir::Expression::dot_member(head, member);
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}
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Ok(head)
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}
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}
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}
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}
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/// A shorthand for `$it.foo."bar"`, used inside of a shorthand block
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#[derive(Debug, Copy, Clone)]
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pub struct ShorthandHeadShape;
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impl FallibleColorSyntax for ShorthandHeadShape {
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type Info = ();
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type Input = ();
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fn color_syntax<'a, 'b>(
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&self,
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_input: &(),
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token_nodes: &'b mut TokensIterator<'a>,
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_context: &ExpandContext,
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shapes: &mut Vec<Tagged<FlatShape>>,
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) -> Result<(), ShellError> {
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// A shorthand path must not be at EOF
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let peeked = token_nodes.peek_non_ws().not_eof("shorthand path")?;
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match peeked.node {
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// If the head of a shorthand path is a bare token, it expands to `$it.bare`
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TokenNode::Token(Tagged {
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item: RawToken::Bare,
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tag,
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}) => {
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peeked.commit();
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shapes.push(FlatShape::BareMember.tagged(tag));
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Ok(())
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}
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// If the head of a shorthand path is a string, it expands to `$it."some string"`
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TokenNode::Token(Tagged {
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item: RawToken::String(_),
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tag: outer,
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}) => {
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peeked.commit();
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shapes.push(FlatShape::StringMember.tagged(outer));
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Ok(())
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}
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other => Err(ShellError::type_error(
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"shorthand head",
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other.tagged_type_name(),
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)),
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}
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}
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}
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impl ExpandExpression for ShorthandHeadShape {
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fn expand_expr<'a, 'b>(
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&self,
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token_nodes: &'b mut TokensIterator<'a>,
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context: &ExpandContext,
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) -> Result<hir::Expression, ShellError> {
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// A shorthand path must not be at EOF
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let peeked = token_nodes.peek_non_ws().not_eof("shorthand path")?;
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match peeked.node {
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// If the head of a shorthand path is a bare token, it expands to `$it.bare`
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TokenNode::Token(Tagged {
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item: RawToken::Bare,
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tag,
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}) => {
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// Commit the peeked token
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peeked.commit();
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// Synthesize an `$it` expression
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let it = synthetic_it(token_nodes.anchor());
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// Make a path out of `$it` and the bare token as a member
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Ok(hir::Expression::path(
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it,
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vec![tag.tagged_string(context.source)],
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tag,
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))
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}
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// If the head of a shorthand path is a string, it expands to `$it."some string"`
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TokenNode::Token(Tagged {
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item: RawToken::String(inner),
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tag: outer,
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}) => {
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// Commit the peeked token
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peeked.commit();
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// Synthesize an `$it` expression
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let it = synthetic_it(token_nodes.anchor());
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// Make a path out of `$it` and the bare token as a member
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Ok(hir::Expression::path(
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it,
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vec![inner.string(context.source).tagged(outer)],
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outer,
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))
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}
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// Any other token is not a valid bare head
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other => {
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return Err(ShellError::type_error(
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"shorthand path",
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other.tagged_type_name(),
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))
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}
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}
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}
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}
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fn synthetic_it(origin: uuid::Uuid) -> hir::Expression {
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hir::Expression::it_variable(Tag::unknown_span(origin), Tag::unknown_span(origin))
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}
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