Consolidate errors in the error module

1 files changed, 169 insertions, 0 deletions

diff --git a/dhall/src/error/mod.rs b/dhall/src/error/mod.rs
new file mode 100644
index 0000000..e70b9a9
--- /dev/null
+++ b/dhall/src/error/mod.rs
@@ -0,0 +1,169 @@
+use std::io::Error as IOError;
+
+use dhall_syntax::{BinOp, Import, Label, ParseError, V};
+
+use crate::phase::resolve::ImportStack;
+use crate::phase::typecheck::TypecheckContext;
+use crate::phase::{Normalized, Type, Typed};
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum Error {
+    IO(IOError),
+    Parse(ParseError),
+    Decode(DecodeError),
+    Resolve(ImportError),
+    Typecheck(TypeError),
+    Deserialize(String),
+}
+
+#[derive(Debug)]
+pub enum ImportError {
+    Recursive(Import, Box<Error>),
+    UnexpectedImport(Import),
+    ImportCycle(ImportStack, Import),
+}
+
+#[derive(Debug)]
+pub enum DecodeError {
+    CBORError(serde_cbor::error::Error),
+    WrongFormatError(String),
+}
+
+/// A structured type error that includes context
+#[derive(Debug)]
+pub struct TypeError {
+    type_message: TypeMessage,
+    context: TypecheckContext,
+}
+
+/// The specific type error
+#[derive(Debug)]
+pub(crate) enum TypeMessage {
+    UnboundVariable(V<Label>),
+    InvalidInputType(Normalized),
+    InvalidOutputType(Normalized),
+    NotAFunction(Typed),
+    TypeMismatch(Typed, Normalized, Typed),
+    AnnotMismatch(Typed, Normalized),
+    Untyped,
+    InvalidListElement(usize, Normalized, Typed),
+    InvalidListType(Normalized),
+    InvalidOptionalType(Normalized),
+    InvalidPredicate(Typed),
+    IfBranchMismatch(Typed, Typed),
+    IfBranchMustBeTerm(bool, Typed),
+    InvalidFieldType(Label, Type),
+    NotARecord(Label, Normalized),
+    MissingRecordField(Label, Typed),
+    MissingUnionField(Label, Normalized),
+    BinOpTypeMismatch(BinOp, Typed),
+    NoDependentTypes(Normalized, Normalized),
+    InvalidTextInterpolation(Typed),
+    Sort,
+    Unimplemented,
+}
+
+impl TypeError {
+    pub(crate) fn new(
+        context: &TypecheckContext,
+        type_message: TypeMessage,
+    ) -> Self {
+        TypeError {
+            context: context.clone(),
+            type_message,
+        }
+    }
+}
+
+impl From<TypeError> for std::option::NoneError {
+    fn from(_: TypeError) -> std::option::NoneError {
+        std::option::NoneError
+    }
+}
+
+impl std::error::Error for TypeMessage {
+    fn description(&self) -> &str {
+        use TypeMessage::*;
+        match *self {
+            // UnboundVariable => "Unbound variable",
+            InvalidInputType(_) => "Invalid function input",
+            InvalidOutputType(_) => "Invalid function output",
+            NotAFunction(_) => "Not a function",
+            TypeMismatch(_, _, _) => "Wrong type of function argument",
+            _ => "Unhandled error",
+        }
+    }
+}
+
+impl std::fmt::Display for TypeMessage {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            // UnboundVariable(_) => {
+            //     f.write_str(include_str!("errors/UnboundVariable.txt"))
+            // }
+            // TypeMismatch(e0, e1, e2) => {
+            //     let template = include_str!("errors/TypeMismatch.txt");
+            //     let s = template
+            //         .replace("$txt0", &format!("{}", e0.as_expr()))
+            //         .replace("$txt1", &format!("{}", e1.as_expr()))
+            //         .replace("$txt2", &format!("{}", e2.as_expr()))
+            //         .replace(
+            //             "$txt3",
+            //             &format!(
+            //                 "{}",
+            //                 e2.get_type()
+            //                     .unwrap()
+            //                     .as_normalized()
+            //                     .unwrap()
+            //                     .as_expr()
+            //             ),
+            //         );
+            //     f.write_str(&s)
+            // }
+            _ => f.write_str("Unhandled error message"),
+        }
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Error::IO(err) => write!(f, "{}", err),
+            Error::Parse(err) => write!(f, "{}", err),
+            Error::Decode(err) => write!(f, "{:?}", err),
+            Error::Resolve(err) => write!(f, "{:?}", err),
+            Error::Typecheck(err) => write!(f, "{:?}", err),
+            Error::Deserialize(err) => write!(f, "{}", err),
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+impl From<IOError> for Error {
+    fn from(err: IOError) -> Error {
+        Error::IO(err)
+    }
+}
+impl From<ParseError> for Error {
+    fn from(err: ParseError) -> Error {
+        Error::Parse(err)
+    }
+}
+impl From<DecodeError> for Error {
+    fn from(err: DecodeError) -> Error {
+        Error::Decode(err)
+    }
+}
+impl From<ImportError> for Error {
+    fn from(err: ImportError) -> Error {
+        Error::Resolve(err)
+    }
+}
+impl From<TypeError> for Error {
+    fn from(err: TypeError) -> Error {
+        Error::Typecheck(err)
+    }
+}