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feat(tvix/eval): emit thunks for recursive local scope resolution

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When resolving a value on the same level that is known but not yet
defined, emit a thunk.

Consider for example:

    let
      #       v--- requires a thunk
      a = 1 * b;
      b = 10;
    in a

Change-Id: I922cb50973ebe05e335a7bc7cb851960cf34733b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6345
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
This commit is contained in:
Vincent Ambo 2022-08-29 00:11:23 +03:00 committed by tazjin
parent d1798444be
commit 28a9847c65
1 changed files with 13 additions and 6 deletions
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19
tvix/eval/src/compiler/mod.rs
View file

@ -120,7 +120,7 @@ impl Compiler {
ast::Expr::Assert(assert) => self.compile_assert(assert),
ast::Expr::IfElse(if_else) => self.compile_if_else(if_else),
ast::Expr::LetIn(let_in) => self.compile_let_in(let_in),
ast::Expr::Ident(ident) => self.compile_ident(ident),
ast::Expr::Ident(ident) => self.compile_ident(slot, ident),
ast::Expr::With(with) => self.compile_with(with),
ast::Expr::Lambda(lambda) => self.compile_lambda(slot, lambda),
ast::Expr::Apply(apply) => self.compile_apply(apply),
@ -620,7 +620,7 @@ impl Compiler {
continue;
}
self.compile_ident(ident.clone());
self.compile_ident(None, ident.clone());
let idx = self.declare_local(
ident.syntax().clone(),
ident.ident_token().unwrap().text(),
@ -702,7 +702,7 @@ impl Compiler {
self.end_scope();
}
fn compile_ident(&mut self, node: ast::Ident) {
fn compile_ident(&mut self, slot: Option<LocalIdx>, node: ast::Ident) {
let ident = node.ident_token().unwrap();
// If the identifier is a global, and it is not poisoned, emit
@ -747,15 +747,22 @@ impl Compiler {
// Variable needs to be dynamically resolved at
// runtime.
self.emit_constant(Value::String(ident.text().into()));
self.chunk().push_op(OpCode::OpResolveWith)
self.chunk().push_op(OpCode::OpResolveWith);
}
LocalPosition::Known(idx) => {
let stack_idx = self.scope().stack_index(idx);
self.chunk().push_op(OpCode::OpGetLocal(stack_idx))
self.chunk().push_op(OpCode::OpGetLocal(stack_idx));
}
LocalPosition::Recursive(_) => panic!("TODO: unclear if this can happen"),
// This identifier is referring to a value from the same
// scope which is not yet defined. This identifier access
// must be thunked.
LocalPosition::Recursive(idx) => self.thunk(slot, move |compiler, _| {
let upvalue_idx =
compiler.add_upvalue(compiler.contexts.len() - 1, Upvalue::Local(idx));
compiler.chunk().push_op(OpCode::OpGetUpvalue(upvalue_idx));
}),
};
}