131 lines
3.2 KiB
Rust
131 lines
3.2 KiB
Rust
use std::borrow::Cow;
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use std::fmt;
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/// Provides context furthering the explanation of *how* you got to an error.
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#[derive(Debug, Clone)]
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pub struct Context(ContextInner);
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impl fmt::Display for Context {
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#[inline(always)]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Display::fmt(&self.0, f)
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}
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}
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#[derive(Debug, Clone)]
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enum ContextInner {
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Elem(ContextElem),
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Compound(Vec<ContextElem>),
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}
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#[derive(Debug, Clone)]
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enum ContextElem {
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Str(&'static str),
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String(String),
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}
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impl fmt::Display for ContextInner {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::Elem(elem) => fmt::Display::fmt(elem, f),
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Self::Compound(elems) => {
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let mut elems = elems.iter();
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if let Some(elem) = elems.next() {
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fmt::Display::fmt(elem, f)?;
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for elem in elems {
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write!(f, "\n{elem}")?;
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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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}
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impl fmt::Display for ContextElem {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::Str(s) => f.write_str(s),
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Self::String(s) => f.write_str(s),
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}
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}
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}
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pub trait IntoContext {
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fn into_context(self) -> Context;
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#[inline(always)]
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fn chain(self, other: impl IntoContext) -> Context
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where
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Self: Sized,
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{
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self.into_context().chain(other)
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}
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}
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impl IntoContext for Context {
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#[inline(always)]
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fn into_context(self) -> Context {
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self
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}
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/// Chains another piece of context that is equal from a hierarchical perspective.
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#[inline]
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fn chain(self, other: impl IntoContext) -> Self {
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Context(ContextInner::Compound(match self.0 {
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ContextInner::Compound(mut elems) => {
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match other.into_context().0 {
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ContextInner::Elem(elem) => elems.push(elem),
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ContextInner::Compound(mut elems1) => elems.append(&mut elems1),
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};
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elems
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}
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ContextInner::Elem(elem) => {
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match other.into_context().0 {
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ContextInner::Elem(elem1) => vec![elem, elem1],
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ContextInner::Compound(mut elems) => {
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elems.insert(0, elem);
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elems
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}
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}
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},
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}))
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}
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}
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impl IntoContext for String {
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#[inline(always)]
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fn into_context(self) -> Context {
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Context(ContextInner::Elem(ContextElem::String(self)))
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}
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}
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impl IntoContext for &'static str {
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#[inline(always)]
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fn into_context(self) -> Context {
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Context(ContextInner::Elem(ContextElem::Str(self)))
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}
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}
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impl IntoContext for Cow<'static, str> {
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#[inline]
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fn into_context(self) -> Context {
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match self {
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Cow::Borrowed(s) => s.into_context(),
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Cow::Owned(s) => s.into_context(),
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}
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}
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}
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impl<C, F> IntoContext for F
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where
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C: IntoContext,
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F: FnOnce() -> C,
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{
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#[inline(always)]
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fn into_context(self) -> Context {
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self().into_context()
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}
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}
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