feat(tvix/eval): carry optional SyntaxNode in error type

This starts paving the way for nicer, source-code based error
reporting.

Right now the code paths in the VM do not emit annotated errors, as we
do not yet preserve that structure from the compiler. However, error
emitting code paths in the compiler have been amended to include known
nodes.

Change-Id: I1b74410ffd891c40cd913361bd73c4336ec8aa5b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6235
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/value/attrs.rs

@@ -10,7 +10,7 @@ use std::collections::BTreeMap;
 use std::fmt::Display;
 use std::rc::Rc;
 
-use crate::errors::{Error, EvalResult};
+use crate::errors::{ErrorKind, EvalResult};
 
 use super::string::NixString;
 use super::Value;
@@ -304,9 +304,10 @@ fn attempt_optimise_kv(slice: &mut [Value]) -> Option<NixAttrs> {
 // checking against duplicate keys.
 fn set_attr(attrs: &mut NixAttrs, key: NixString, value: Value) -> EvalResult<()> {
     match attrs.0.map_mut().entry(key) {
-        btree_map::Entry::Occupied(entry) => Err(Error::DuplicateAttrsKey {
+        btree_map::Entry::Occupied(entry) => Err(ErrorKind::DuplicateAttrsKey {
             key: entry.key().as_str().to_string(),
-        }),
+        }
+        .into()),
 
         btree_map::Entry::Vacant(entry) => {
             entry.insert(value);
@@ -365,9 +366,10 @@ fn set_nested_attr(
             }
 
             _ => {
-                return Err(Error::DuplicateAttrsKey {
+                return Err(ErrorKind::DuplicateAttrsKey {
                     key: entry.key().as_str().to_string(),
-                })
+                }
+                .into())
             }
         },
     }

tvix/eval/src/value/mod.rs

@@ -7,7 +7,7 @@ mod attrs;
 mod list;
 mod string;
 
-use crate::errors::{Error, EvalResult};
+use crate::errors::{ErrorKind, EvalResult};
 pub use attrs::NixAttrs;
 pub use list::NixList;
 pub use string::NixString;
@@ -55,50 +55,55 @@ impl Value {
     pub fn as_bool(&self) -> EvalResult<bool> {
         match self {
             Value::Bool(b) => Ok(*b),
-            other => Err(Error::TypeError {
+            other => Err(ErrorKind::TypeError {
                 expected: "bool",
                 actual: other.type_of(),
-            }),
+            }
+            .into()),
         }
     }
 
     pub fn as_attrs(&self) -> EvalResult<&NixAttrs> {
         match self {
             Value::Attrs(attrs) => Ok(attrs),
-            other => Err(Error::TypeError {
+            other => Err(ErrorKind::TypeError {
                 expected: "set",
                 actual: other.type_of(),
-            }),
+            }
+            .into()),
         }
     }
 
     pub fn to_string(self) -> EvalResult<NixString> {
         match self {
             Value::String(s) => Ok(s),
-            other => Err(Error::TypeError {
+            other => Err(ErrorKind::TypeError {
                 expected: "string",
                 actual: other.type_of(),
-            }),
+            }
+            .into()),
         }
     }
 
     pub fn to_attrs(self) -> EvalResult<Rc<NixAttrs>> {
         match self {
             Value::Attrs(s) => Ok(s),
-            other => Err(Error::TypeError {
+            other => Err(ErrorKind::TypeError {
                 expected: "set",
                 actual: other.type_of(),
-            }),
+            }
+            .into()),
         }
     }
 
     pub fn to_list(self) -> EvalResult<NixList> {
         match self {
             Value::List(l) => Ok(l),
-            other => Err(Error::TypeError {
+            other => Err(ErrorKind::TypeError {
                 expected: "list",
                 actual: other.type_of(),
-            }),
+            }
+            .into()),
         }
     }