diff options
| -rw-r--r-- | tvix/eval/src/compiler/mod.rs | 31 | ||||
| -rw-r--r-- | tvix/eval/src/errors.rs | 3 |
2 files changed, 34 insertions, 0 deletions
diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs index 38eaddddc1..eefcbfcd65 100644 --- a/tvix/eval/src/compiler/mod.rs +++ b/tvix/eval/src/compiler/mod.rs @@ -54,6 +54,14 @@ impl Depth { Depth::At(ours) => *ours > theirs, } } + + /// Does this variable live below the other given depth? + fn below(&self, theirs: usize) -> bool { + match self { + Depth::Unitialised => false, + Depth::At(ours) => *ours < theirs, + } + } } /// Represents a single local already known to the compiler. @@ -1013,6 +1021,26 @@ impl Compiler { self.scope_mut().poison(global_ident, depth); } + let mut shadowed = false; + for local in self.scope().locals.iter().rev() { + if local.depth.below(self.scope().scope_depth) { + // Shadowing identifiers from higher scopes is allowed. + break; + } + + if local.name == name { + shadowed = true; + break; + } + } + + if shadowed { + self.emit_error( + node.clone(), + ErrorKind::VariableAlreadyDefined(name.clone()), + ); + } + self.scope_mut().locals.push(Local { name, depth: Depth::At(depth), @@ -1022,6 +1050,9 @@ impl Compiler { }); } + /// Declare a local variable that occupies a stack slot and should + /// be accounted for, but is not directly accessible by users + /// (e.g. attribute sets used for `with`). fn declare_phantom(&mut self) { let depth = self.scope().scope_depth; self.scope_mut().locals.push(Local { diff --git a/tvix/eval/src/errors.rs b/tvix/eval/src/errors.rs index 96217cabaf..49a051c16e 100644 --- a/tvix/eval/src/errors.rs +++ b/tvix/eval/src/errors.rs @@ -32,6 +32,9 @@ pub enum ErrorKind { // Unknown variable in dynamic scope (with, rec, ...). UnknownDynamicVariable(String), + // User is defining the same variable twice at the same depth. + VariableAlreadyDefined(String), + // Attempt to call something that is not callable. NotCallable, |