Fix broken constants in scopes (#9679)

crates/nu-cmd-lang/src/core_commands/const_.rs

@@ -47,15 +47,17 @@ impl Command for Const {
         call: &Call,
         _input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let var_id = call
-            .positional_nth(0)
-            .expect("checked through parser")
-            .as_var()
-            .expect("internal error: missing variable");
+        let var_id = if let Some(id) = call.positional_nth(0).and_then(|pos| pos.as_var()) {
+            id
+        } else {
+            return Err(ShellError::NushellFailedSpanned {
+                msg: "Could not get variable".to_string(),
+                label: "variable not added by the parser".to_string(),
+                span: call.head,
+            });
+        };
 
-        if let Some(constval) = engine_state.find_constant(var_id, &[]) {
-            // Instead of creating a second copy of the value in the stack, we could change
-            // stack.get_var() to check engine_state.find_constant().
+        if let Some(constval) = &engine_state.get_var(var_id).const_val {
             stack.add_var(var_id, constval.clone());
 
             Ok(PipelineData::empty())

crates/nu-engine/src/env.rs

@@ -294,9 +294,7 @@ pub fn find_in_dirs_env(
             .flatten()
     };
 
-    let lib_dirs = dirs_var
-        .and_then(|dirs_var| engine_state.find_constant(dirs_var, &[]))
-        .cloned();
+    let lib_dirs = dirs_var.and_then(|var_id| engine_state.get_var(var_id).const_val.clone());
     // TODO: remove (see #8310)
     let lib_dirs_fallback = stack.get_env_var(engine_state, "NU_LIB_DIRS");
 

crates/nu-parser/src/eval.rs

@@ -23,7 +23,7 @@ pub fn eval_constant(
             val: path.clone(),
             span: expr.span,
         }),
-        Expr::Var(var_id) => match working_set.find_constant(*var_id) {
+        Expr::Var(var_id) => match working_set.get_variable(*var_id).const_val.as_ref() {
             Some(val) => Ok(val.clone()),
             None => Err(ParseError::NotAConstant(expr.span)),
         },

crates/nu-parser/src/parse_keywords.rs

@@ -2958,6 +2958,7 @@ pub fn parse_const(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipelin
                             .trim_start_matches('$')
                             .to_string();
 
+                    // TODO: Remove the hard-coded variables, too error-prone
                     if ["in", "nu", "env", "nothing"].contains(&var_name.as_str()) {
                         working_set.error(ParseError::NameIsBuiltinVar(var_name, lvalue.span))
                     }
@@ -2982,7 +2983,25 @@ pub fn parse_const(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipelin
 
                         match eval_constant(working_set, &rvalue) {
                             Ok(val) => {
-                                working_set.add_constant(var_id, val);
+                                // In case rhs is parsed as 'any' but is evaluated to a concrete
+                                // type:
+                                let const_type = val.get_type();
+
+                                if let Some(explicit_type) = &explicit_type {
+                                    if !type_compatible(explicit_type, &const_type) {
+                                        working_set.error(ParseError::TypeMismatch(
+                                            explicit_type.clone(),
+                                            const_type.clone(),
+                                            nu_protocol::span(&spans[(span.0 + 1)..]),
+                                        ));
+                                    }
+                                }
+
+                                working_set.set_variable_type(var_id, const_type);
+
+                                // Assign the constant value to the variable
+                                working_set.set_variable_const_val(var_id, val);
+                                // working_set.add_constant(var_id, val);
                             }
                             Err(err) => working_set.error(err),
                         }
@@ -3527,7 +3546,7 @@ pub fn parse_register(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipe
 pub fn find_dirs_var(working_set: &StateWorkingSet, var_name: &str) -> Option<VarId> {
     working_set
         .find_variable(format!("${}", var_name).as_bytes())
-        .filter(|var_id| working_set.find_constant(*var_id).is_some())
+        .filter(|var_id| working_set.get_variable(*var_id).const_val.is_some())
 }
 
 /// This helper function is used to find files during parsing
@@ -3595,7 +3614,9 @@ pub fn find_in_dirs(
 
         // Look up relative path from NU_LIB_DIRS
         working_set
-            .find_constant(find_dirs_var(working_set, dirs_var_name)?)?
+            .get_variable(find_dirs_var(working_set, dirs_var_name)?)
+            .const_val
+            .as_ref()?
             .as_list()
             .ok()?
             .iter()

crates/nu-protocol/src/engine/engine_state.rs

@@ -233,9 +233,6 @@ impl EngineState {
                 for item in delta_overlay.vars.into_iter() {
                     existing_overlay.vars.insert(item.0, item.1);
                 }
-                for item in delta_overlay.constants.into_iter() {
-                    existing_overlay.constants.insert(item.0, item.1);
-                }
                 for item in delta_overlay.modules.into_iter() {
                     existing_overlay.modules.insert(item.0, item.1);
                 }
@@ -727,16 +724,6 @@ impl EngineState {
         output
     }
 
-    pub fn find_constant(&self, var_id: VarId, removed_overlays: &[Vec<u8>]) -> Option<&Value> {
-        for overlay_frame in self.active_overlays(removed_overlays).rev() {
-            if let Some(val) = overlay_frame.constants.get(&var_id) {
-                return Some(val);
-            }
-        }
-
-        None
-    }
-
     pub fn get_span_contents(&self, span: &Span) -> &[u8] {
         for (contents, start, finish) in &self.file_contents {
             if span.start >= *start && span.end <= *finish {
@@ -1639,23 +1626,13 @@ impl<'a> StateWorkingSet<'a> {
         }
     }
 
-    pub fn add_constant(&mut self, var_id: VarId, val: Value) {
-        self.last_overlay_mut().constants.insert(var_id, val);
+    pub fn set_variable_const_val(&mut self, var_id: VarId, val: Value) {
+        let num_permanent_vars = self.permanent_state.num_vars();
+        if var_id < num_permanent_vars {
+            panic!("Internal error: attempted to set into permanent state from working set")
+        } else {
+            self.delta.vars[var_id - num_permanent_vars].const_val = Some(val);
         }
-
-    pub fn find_constant(&self, var_id: VarId) -> Option<&Value> {
-        let mut removed_overlays = vec![];
-
-        for scope_frame in self.delta.scope.iter().rev() {
-            for overlay_frame in scope_frame.active_overlays(&mut removed_overlays).rev() {
-                if let Some(val) = overlay_frame.constants.get(&var_id) {
-                    return Some(val);
-                }
-            }
-        }
-
-        self.permanent_state
-            .find_constant(var_id, &removed_overlays)
     }
 
     pub fn get_variable(&self, var_id: VarId) -> &Variable {

crates/nu-protocol/src/engine/overlay.rs

@@ -1,4 +1,4 @@
-use crate::{DeclId, ModuleId, OverlayId, Value, VarId};
+use crate::{DeclId, ModuleId, OverlayId, VarId};
 use std::collections::HashMap;
 
 pub static DEFAULT_OVERLAY_NAME: &str = "zero";
@@ -177,7 +177,6 @@ impl ScopeFrame {
 #[derive(Debug, Clone)]
 pub struct OverlayFrame {
     pub vars: HashMap<Vec<u8>, VarId>,
-    pub constants: HashMap<VarId, Value>,
     pub predecls: HashMap<Vec<u8>, DeclId>, // temporary storage for predeclarations
     pub decls: HashMap<Vec<u8>, DeclId>,
     pub modules: HashMap<Vec<u8>, ModuleId>,
@@ -190,7 +189,6 @@ impl OverlayFrame {
     pub fn from_origin(origin: ModuleId, prefixed: bool) -> Self {
         Self {
             vars: HashMap::new(),
-            constants: HashMap::new(),
             predecls: HashMap::new(),
             decls: HashMap::new(),
             modules: HashMap::new(),

crates/nu-protocol/src/variable.rs

@@ -1,10 +1,11 @@
-use crate::{Span, Type};
+use crate::{Span, Type, Value};
 
 #[derive(Clone, Debug)]
 pub struct Variable {
     pub declaration_span: Span,
     pub ty: Type,
     pub mutable: bool,
+    pub const_val: Option<Value>,
 }
 
 impl Variable {
@@ -13,6 +14,7 @@ impl Variable {
             declaration_span,
             ty,
             mutable,
+            const_val: None,
         }
     }
 }

tests/const_/mod.rs

@@ -102,3 +102,12 @@ fn const_unsupported() {
 
     assert!(actual.err.contains("not_a_constant"));
 }
+
+#[test]
+fn const_in_scope() {
+    let inp = &["do { const x = 'x'; $x }"];
+
+    let actual = nu!(&inp.join("; "));
+
+    assert_eq!(actual.out, "x");
+}