feat(tvix/eval): implement chunk disassembler output

This makes for a much nicer view of an execution if `--feature
disassembler` is set, for example:

  tvix-repl> let value = [ 1 2 { a = 1; } ]; in value ++ [ 1 ]
  === compiled bytecode (11 operations) ===
  02   OpConstant(1)
  02   OpConstant(2)
  02   OpConstant("a")
  02   OpConstant(1)
  02   OpAttrs(1)
  02   OpList(3)
  02   OpGetLocal(0)
  02   OpConstant(1)
  02   OpList(1)
  02   OpConcat
  02   OpCloseScope(1)
  === runtime trace ===
  0001 OpConstant(ConstantIdx(0))  [ 1 ]
  0002 OpConstant(ConstantIdx(1))  [ 1 2 ]
  0003 OpConstant(ConstantIdx(2))  [ 1 2 "a" ]
  0004 OpConstant(ConstantIdx(3))  [ 1 2 "a" 1 ]
  0005 OpAttrs(1)                  [ 1 2 { a = 1; } ]
  0006 OpList(3)                   [ [ 1 2 { a = 1; } ] ]
  0007 OpGetLocal(0)               [ [ 1 2 { a = 1; } ] [ 1 2 { a = 1; } ] ]
  0008 OpConstant(ConstantIdx(4))  [ [ 1 2 { a = 1; } ] [ 1 2 { a = 1; } ] 1 ]
  0009 OpList(1)                   [ [ 1 2 { a = 1; } ] [ 1 2 { a = 1; } ] [ 1 ] ]
  0010 OpConcat                    [ [ 1 2 { a = 1; } ] [ 1 2 { a = 1; } 1 ] ]
  0011 OpCloseScope(1)             [ [ 1 2 { a = 1; } 1 ] ]
  => [ 1 2 { a = 1; } 1 ] :: list

Change-Id: If79c7fd1f0f18255ddb3763c1ba585fda8041b1b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6195
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

tvix/eval/src/eval.rs

@@ -17,7 +17,9 @@ pub fn interpret(code: &str, location: Option<PathBuf>) -> EvalResult<Value> {
     }
 
     let result = crate::compiler::compile(ast, location)?;
-    println!("code: {:?}", result.chunk);
+
+    #[cfg(feature = "disassembler")]
+    crate::disassembler::disassemble_chunk(&result.chunk);
 
     for warning in result.warnings {
         eprintln!(