Enum nom_supreme::error::ErrorTree [−][src]
pub enum ErrorTree<I> { Base { location: I, kind: BaseErrorKind, }, Stack { base: Box<Self>, contexts: Vec<(I, StackContext)>, }, Alt(Vec<Self>), }
Expand description
A comprehensive tree of nom errors describing a parse failure.
This Error type is designed to be VerboseError
++
. While
VerboseError
can represent a stack of errors, this type can represent
a full tree. In addition to representing a particular specific parse error,
it can also represent a stack of nested error contexts (for instance, as
provided by context
), or a list of alternatives
that were all tried individually by alt
and all
failed.
In general, the design goal for this type is to discard as little useful
information as possible. That being said, many ErrorKind
variants add
very little useful contextual information to error traces; for example,
ErrorKind::Alt
doesn’t add any interesting context to an
ErrorTree::Alt
, and its presence in a stack precludes merging together
adjacent sets of ErrorTree::Alt
siblings.
Examples
Base parser errors
An ErrorTree::Base
is an error that occurred at the “bottom” of the stack,
from a parser looking for 1 specific kind of thing.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::character::complete::{digit1, char}; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; let err: Err<ErrorTree<&str>> = digit1.parse("abc").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Base{ location: "abc", kind: BaseErrorKind::Expected(Expectation::Digit), })); let err: Err<ErrorTree<&str>> = char('a').and(char('b')).parse("acb").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Base{ location: "cb", kind: BaseErrorKind::Expected(Expectation::Char('b')), }));
Stacks
An ErrorTree::Stack
is created when a parser combinator—typically
context
—attaches additional error context to a subparser error. It can
have any ErrorTree
at the base of the stack.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::character::complete::{alpha1, space1, char,}; use nom::sequence::{separated_pair, delimited}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; // Parse a single identifier, defined as just a string of letters. let identifier = alpha1.context("identifier"); // Parse a pair of identifiers, separated by whitespace let identifier_pair = separated_pair(identifier, space1, identifier) .context("identifier pair"); // Parse a pair of identifiers in parenthesis. let mut parenthesized = delimited(char('('), identifier_pair, char(')')) .context("parenthesized"); let err: Err<ErrorTree<&str>> = parenthesized.parse("(abc 123)").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Stack { base, contexts, }) => { assert_matches!(*base, ErrorTree::Base { location: "123)", kind: BaseErrorKind::Expected(Expectation::Alpha) }); assert_eq!(contexts, [ ("123)", StackContext::Context("identifier")), ("abc 123)", StackContext::Context("identifier pair")), ("(abc 123)", StackContext::Context("parenthesized")), ]); });
Alternatives
An ErrorTree::Alt
is created when a series of parsers are all tried,
and all of them fail. Most commonly this will happen via the
alt
combinator or the equivalent .or
postfix
combinator. When all of these subparsers fail, their errors (each
individually their own ErrorTree
) are aggregated into an
ErrorTree::Alt
, indicating that “any one of these things were
expected.”
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::branch::alt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::tag::complete::tag; let parse_bool = alt(( tag("true").value(true), tag("false").value(false), )); let mut parse_null_bool = alt(( parse_bool.map(Some), tag("null").value(None), )); assert_eq!(parse_null_bool.parse("true").unwrap(), ("", Some(true))); assert_eq!(parse_null_bool.parse("false").unwrap(), ("", Some(false))); assert_eq!(parse_null_bool.parse("null").unwrap(), ("", None)); let err: Err<ErrorTree<&str>> = parse_null_bool.parse("123").unwrap_err(); // This error communicates to the caller that any one of "true", "false", // or "null" was expected at that location. assert_matches!(err, Err::Error(ErrorTree::Alt(choices)) => { assert_matches!(choices.as_slice(), [ ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("true"))}, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("false"))}, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("null"))}, ]) });
Contexts and Alternatives
Because Stack
and Alt
recursively contain ErrorTree
errors from
subparsers, they can be can combined to create error trees of arbitrary
complexity.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::branch::alt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::tag::complete::tag; let parse_bool = alt(( tag("true").value(true), tag("false").value(false), )).context("bool"); let mut parse_null_bool = alt(( parse_bool.map(Some), tag("null").value(None).context("null"), )).context("null or bool"); assert_eq!(parse_null_bool.parse("true").unwrap(), ("", Some(true))); assert_eq!(parse_null_bool.parse("false").unwrap(), ("", Some(false))); assert_eq!(parse_null_bool.parse("null").unwrap(), ("", None)); let err: Err<ErrorTree<&str>> = parse_null_bool.parse("123").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Stack{base, contexts}) => { assert_eq!(contexts, [("123", StackContext::Context("null or bool"))]); assert_matches!(*base, ErrorTree::Alt(choices) => { assert_matches!(&choices[0], ErrorTree::Stack{base, contexts} => { assert_eq!(contexts, &[("123", StackContext::Context("bool"))]); assert_matches!(&**base, ErrorTree::Alt(choices) => { assert_matches!(&choices[0], ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("true")) }); assert_matches!(&choices[1], ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("false")) }); }); }); assert_matches!(&choices[1], ErrorTree::Stack{base, contexts} => { assert_eq!(contexts, &[("123", StackContext::Context("null"))]); assert_matches!(&**base, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("null")) }); }); }); });
Display formatting
TODO WRITE THIS SECTION
Variants
A specific error event at a specific location. Often this will indicate that something like a tag or character was expected at that location.
Fields of Base
location: I
The location of this error in the input
kind: BaseErrorKind
The specific error that occurred
A stack indicates a chain of error contexts was provided. The stack
should be read “backwards”; that is, errors earlier in the Vec
occurred “sooner” (deeper in the call stack).
Fields of Stack
base: Box<Self>
The original error
contexts: Vec<(I, StackContext)>
The stack of contexts attached to that error
A series of parsers were tried at the same location (for instance, via
the alt
combinator) and all of them failed. All
of the errors in this set are “siblings”.
Tuple Fields of Alt
0: Vec<Self>
Implementations
Convert all of the locations in this error using some kind of mapping function. This is intended to help add additional context that may not have been available when the nom parsers were running, such as line and column numbers.
Trait Implementations
Similar to append: Create a new error with some added context
impl<I, T> ExtractContext<I, ErrorTree<T>> for ErrorTree<I> where
I: Clone,
T: RecreateContext<I>,
impl<I, T> ExtractContext<I, ErrorTree<T>> for ErrorTree<I> where
I: Clone,
T: RecreateContext<I>,
Given the context attached to a nom error, and given the original input to the nom parser, extract more the useful context information. Read more
Create an error from a given external error, such as from FromStr
Create a new error at the given position. Interpret kind
as an
Expectation
if possible, to give a more informative error message.
Combine an existing error with a new one. This is how error context is accumulated when backtracing. “other” is the original error, and the inputs new error from higher in the call stack.
If other
is already an ErrorTree::Stack
, the context is added to
the stack; otherwise, a new stack is created, with other
at the root.
Create an error indicating an expected character at a given position
Combine two errors from branches of alt. If either or both errors are
already ErrorTree::Alt
, the different error sets are merged;
otherwise, a new ErrorTree::Alt
is created, containing both
self
and other
.
Auto Trait Implementations
impl<I> !RefUnwindSafe for ErrorTree<I>
impl<I> !UnwindSafe for ErrorTree<I>
Blanket Implementations
Mutably borrows from an owned value. Read more
Given the context attached to a nom error, and given the original input to the nom parser, extract more the useful context information. Read more
fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
Causes self
to use its Binary
implementation when Debug
-formatted.
fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
Causes self
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Debug
-formatted. Read more
fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
Causes self
to use its LowerExp
implementation when
Debug
-formatted. Read more
fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
Causes self
to use its LowerHex
implementation when
Debug
-formatted. Read more
Causes self
to use its Octal
implementation when Debug
-formatted.
fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
Causes self
to use its Pointer
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Debug
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fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
Causes self
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Debug
-formatted. Read more
fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
Causes self
to use its UpperHex
implementation when
Debug
-formatted. Read more
impl<T> Pipe for T where
T: ?Sized,
impl<T> Pipe for T where
T: ?Sized,
Pipes by value. This is generally the method you want to use. Read more
Borrows self
and passes that borrow into the pipe function. Read more
fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R where
R: 'a,
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Mutably borrows self
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R: 'a,
B: 'a + ?Sized,
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Self: Borrow<B>,
R: 'a,
B: 'a + ?Sized,
Borrows self
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fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
R: 'a,
B: 'a + ?Sized,
fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
R: 'a,
B: 'a + ?Sized,
Mutably borrows self
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R: 'a,
U: 'a + ?Sized,
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Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
Borrows self
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into the pipe function.
fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
Mutably borrows self
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fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
Borrows self
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fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_as_mut<'a, T, R>(&'a mut self, func: impl FnOnce(&'a mut T) -> R) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
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Self: AsMut<T>,
T: 'a,
R: 'a,
Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
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Self: Borrow<T>,
T: 'a,
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Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more
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Pipes a dereference into a function that cannot normally be called in suffix position. Read more
fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
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fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
Pipes a mutable dereference into a function that cannot normally be called in suffix position. Read more
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Given the original input, as well as the context reported by nom, recreate a context in the original string where the error occurred. Read more
fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
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B: ?Sized,
Immutable access to the Borrow<B>
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fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Self where
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fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
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R: ?Sized,
Mutable access to the AsMut<R>
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Mutable access to the Deref::Target
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Calls .tap()
only in debug builds, and is erased in release builds.
fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
Calls .tap_mut()
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fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Calls .tap_borrow()
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fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Self where
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B: ?Sized,
Calls .tap_borrow_mut()
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fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Calls .tap_ref()
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fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Calls .tap_ref_mut()
only in debug builds, and is erased in release
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Provides immutable access for inspection. Read more
Calls tap
in debug builds, and does nothing in release builds.
Provides mutable access for modification. Read more
fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
Calls tap_mut
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impl<T, U> TapAsRef<U> for T where
U: ?Sized,
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U: ?Sized,
Provides immutable access to the reference for inspection.
fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Calls tap_ref
in debug builds, and does nothing in release builds.
fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Provides mutable access to the reference for modification.
fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Calls tap_ref_mut
in debug builds, and does nothing in release builds.
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Provides immutable access to the borrow for inspection. Read more
fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Calls tap_borrow
in debug builds, and does nothing in release builds.
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Provides mutable access to the borrow for modification.
fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Calls tap_borrow_mut
in debug builds, and does nothing in release
builds. Read more
Immutably dereferences self
for inspection.
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Calls tap_deref
in debug builds, and does nothing in release builds.
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Mutably dereferences self
for modification.
fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Calls tap_deref_mut
in debug builds, and does nothing in release
builds. Read more