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|
use std::{
error::Error,
fmt::{self, Display},
};
use proc_macro2::Span;
use crate::chomp::{name::Name, ast::{Call, Fix, Lambda, Let, Variable}};
use super::{Type, TypedExpression, context::GetVariableError};
/// A type error when using a fix point variable.
#[derive(Debug)]
pub struct VariableError {
pub inner: GetVariableError,
pub var: Variable,
pub span: Span,
pub name: Option<Name>,
}
impl Display for VariableError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.inner {
GetVariableError::FreeVariable => write!(f, "unbound variable: "),
GetVariableError::GuardedVariable => write!(f, "usage of guarded variable: "),
}?;
if let Some(name) = &self.name {
write!(f, "`{}`", name)
} else {
write!(f, "'{}", self.var.index)
}
}
}
impl Error for VariableError {}
#[derive(Debug)]
pub enum CatError {
FirstNullable {
expr: TypedExpression,
punct: Span,
},
FirstFlastOverlap {
front_ty: Type,
punct: Span,
next: TypedExpression,
},
}
impl CatError {
pub fn span(&self) -> Span {
match self {
Self::FirstNullable { punct, .. } | Self::FirstFlastOverlap { punct, .. } => *punct,
}
}
}
impl Display for CatError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::FirstNullable { .. } => write!(f, "first part of concatenation is nullable"),
Self::FirstFlastOverlap { .. } => {
write!(f, "first set overlaps with preceding flast set")
}
}
}
}
impl Error for CatError {}
#[derive(Debug)]
pub enum AltError {
BothNullable {
left_ty: Type,
punct: Span,
right: TypedExpression,
},
FirstOverlap {
left_ty: Type,
punct: Span,
right: TypedExpression,
},
}
impl AltError {
pub fn span(&self) -> Span {
match self {
Self::BothNullable { punct, .. } | Self::FirstOverlap { punct, .. } => *punct,
}
}
}
impl Display for AltError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::BothNullable { .. } => write!(f, "both branches are nullable"),
Self::FirstOverlap { .. } => write!(f, "first sets of both branches overlap"),
}
}
}
impl Error for AltError {}
#[derive(Debug)]
pub enum TypeError {
Cat(CatError),
Alt(AltError),
Variable(VariableError),
UnexpectedCall { span: Span, call: Call },
UnexpectedLambda { span: Span, lambda: Lambda },
UnexpectedLet { span: Span, stmt: Let },
ExpectedLambda {span: Span, fix: Fix },
}
impl TypeError {
pub fn span(&self) -> Span {
match self {
TypeError::Cat(c) => c.span(),
TypeError::Alt(a) => a.span(),
TypeError::Variable(v) => v.span,
TypeError::UnexpectedCall { span, .. }
| TypeError::UnexpectedLambda { span, .. }
| TypeError::UnexpectedLet { span, .. }
| TypeError::ExpectedLambda { span, .. } => *span,
}
}
}
impl From<CatError> for TypeError {
fn from(other: CatError) -> Self {
Self::Cat(other)
}
}
impl From<AltError> for TypeError {
fn from(other: AltError) -> Self {
Self::Alt(other)
}
}
impl From<VariableError> for TypeError {
fn from(other: VariableError) -> Self {
Self::Variable(other)
}
}
impl From<TypeError> for syn::Error {
fn from(other: TypeError) -> Self {
let span = other.span();
let msg = format!("{}", other);
Self::new(span, msg)
}
}
impl Display for TypeError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Cat(e) => e.fmt(f),
Self::Alt(e) => e.fmt(f),
Self::Variable(e) => e.fmt(f),
Self::UnexpectedCall { .. } => {
write!(f, "unexpected call")
}
Self::UnexpectedLambda { .. } => {
write!(f, "unexpected lambda")
}
Self::UnexpectedLet { .. } => {
write!(f, "unexpected let")
}
Self::ExpectedLambda { .. } => {
write!(f, "expected a lambda expression")
}
}
}
}
impl Error for TypeError {}
|
