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/vm.rs

@@ -5,7 +5,7 @@ use std::rc::Rc;
 
 use crate::{
     chunk::Chunk,
-    errors::{Error, EvalResult},
+    errors::{ErrorKind, EvalResult},
     opcode::OpCode,
     value::{NixAttrs, NixList, Value},
 };
@@ -38,14 +38,14 @@ macro_rules! arithmetic_op {
             (Value::Integer(i1), Value::Float(f2)) => Value::Float(i1 as f64 $op f2),
             (Value::Float(f1), Value::Integer(i2)) => Value::Float(f1 $op i2 as f64),
 
-            (v1, v2) => return Err(Error::TypeError {
+            (v1, v2) => return Err(ErrorKind::TypeError {
                 expected: "number (either int or float)",
                 actual: if v1.is_number() {
                     v2.type_of()
                 } else {
                     v1.type_of()
                 },
-            }),
+            }.into()),
         }
     }};
 }
@@ -65,10 +65,10 @@ macro_rules! cmp_op {
             (Value::Float(f1), Value::Integer(i2)) => f1 $op (i2 as f64),
             (Value::String(s1), Value::String(s2)) => s1 $op s2,
 
-            (lhs, rhs) => return Err(Error::Incomparable {
+            (lhs, rhs) => return Err(ErrorKind::Incomparable {
                 lhs: lhs.type_of(),
                 rhs: rhs.type_of(),
-            }),
+            }.into()),
         };
 
         $self.push(Value::Bool(result));
@@ -136,10 +136,11 @@ impl VM {
                     Value::Integer(i) => self.push(Value::Integer(-i)),
                     Value::Float(f) => self.push(Value::Float(-f)),
                     v => {
-                        return Err(Error::TypeError {
+                        return Err(ErrorKind::TypeError {
                             expected: "number (either int or float)",
                             actual: v.type_of(),
-                        })
+                        }
+                        .into())
                     }
                 },
 
@@ -177,9 +178,10 @@ impl VM {
                         Some(value) => self.push(value.clone()),
 
                         None => {
-                            return Err(Error::AttributeNotFound {
+                            return Err(ErrorKind::AttributeNotFound {
                                 name: key.as_str().to_string(),
-                            })
+                            }
+                            .into())
                         }
                     }
                 }
@@ -255,10 +257,11 @@ impl VM {
                 OpCode::OpAssertBool => {
                     let val = self.peek(0);
                     if !val.is_bool() {
-                        return Err(Error::TypeError {
+                        return Err(ErrorKind::TypeError {
                             expected: "bool",
                             actual: val.type_of(),
-                        });
+                        }
+                        .into());
                     }
                 }
 
@@ -302,12 +305,12 @@ impl VM {
                         }
                     }
 
-                    return Err(Error::UnknownDynamicVariable(ident.to_string()));
+                    return Err(ErrorKind::UnknownDynamicVariable(ident.to_string()).into());
                 }
 
                 OpCode::OpAssert => {
                     if !self.pop().as_bool()? {
-                        return Err(Error::AssertionFailed);
+                        return Err(ErrorKind::AssertionFailed.into());
                     }
                 }
             }