tamer: src::pipeline: Eliminate most error type references

Just cleaning up a bit, removing some unnecessary types, since there are so
many involved.

DEV-13162

tamer/src/parse.rs

@@ -31,7 +31,8 @@ pub mod util;
 
 pub use error::{FinalizeError, ParseError};
 pub use lower::{
-    lowerable, terminal, Lower, LowerIter, LowerSource, ParsedObject,
+    lowerable, terminal, FromParseError, Lower, LowerIter, LowerSource,
+    ParsedObject,
 };
 pub use parser::{FinalizedParser, Parsed, ParsedResult, Parser};
 pub use state::{

tamer/src/parse/lower.rs

@@ -239,6 +239,16 @@ pub trait WidenedError<S: ParseState, LS: ParseState> = Diagnostic
     + From<ParseError<<S as ParseState>::Token, <S as ParseState>::Error>>
     + From<ParseError<<LS as ParseState>::Token, <LS as ParseState>::Error>>;
 
+/// Convenience trait for converting [`From`] a [`ParseError`] for the
+///   provided [`ParseState`] `S`.
+///
+/// This allows specifying this type in terms of only the [`ParseState`]
+///   that is almost certainly already utilized,
+///     rather than having to either import more types or use the verbose
+///     associated type.
+pub trait FromParseError<S: ParseState> =
+    From<ParseError<<S as ParseState>::Token, <S as ParseState>::Error>>;
+
 /// A [`ParsedResult`](super::ParsedResult) with a [`WidenedError`].
 pub type WidenedParsedResult<S, E> =
     Result<Parsed<<S as ParseState>::Object>, E>;

tamer/src/pipeline.rs

@@ -41,21 +41,15 @@
 //!   see [`Lower`].
 
 use crate::{
-    asg::{
-        air::{Air, AirAggregate, AirAggregateCtx},
-        AsgError,
-    },
+    asg::air::{AirAggregate, AirAggregateCtx},
     diagnose::Diagnostic,
-    obj::xmlo::{
-        XmloAirContext, XmloAirError, XmloError, XmloReader, XmloToAir,
-        XmloToken,
-    },
+    obj::xmlo::{XmloAirContext, XmloReader, XmloToAir, XmloToken},
     parse::{
-        FinalizeError, Lower, LowerSource, ParseError, Parsed, ParsedObject,
-        UnknownToken,
+        FinalizeError, FromParseError, Lower, LowerSource, ParseError, Parsed,
+        ParsedObject, UnknownToken,
     },
     xir::{
-        flat::{PartialXirToXirf, Text, XirToXirfError, XirfToken},
+        flat::{PartialXirToXirf, Text},
         Error as XirError, Token as XirToken,
     },
 };
@@ -76,10 +70,10 @@ pub fn load_xmlo<EO: Diagnostic + PartialEq>(
 ) -> Result<(AirAggregateCtx, XmloAirContext), EO>
 where
     EO: From<ParseError<UnknownToken, XirError>>
-        + From<ParseError<XirfToken<Text>, XmloError>>
-        + From<ParseError<XirToken, XirToXirfError>>
-        + From<ParseError<XmloToken, XmloAirError>>
-        + From<ParseError<Air, AsgError>>
+        + FromParseError<PartialXirToXirf<4, Text>>
+        + FromParseError<XmloReader>
+        + FromParseError<XmloToAir>
+        + FromParseError<AirAggregate>
         + From<FinalizeError>,
 {
     // TODO: This entire block is a WIP and will be incrementally