Add docs and an unused function for fun

dust-lang/src/context.rs

@@ -1,15 +1,17 @@
 //! Garbage-collecting context for variables.
 use std::{
     collections::HashMap,
-    sync::{Arc, RwLock},
+    sync::{Arc, PoisonError as StdPoisonError, RwLock, RwLockWriteGuard},
 };
 
 use crate::{Identifier, Span, Type, Value};
 
+pub type Variables = HashMap<Identifier, (VariableData, Span)>;
+
 /// Garbage-collecting context for variables.
 #[derive(Debug, Clone)]
 pub struct Context {
-    variables: Arc<RwLock<HashMap<Identifier, (VariableData, Span)>>>,
+    variables: Arc<RwLock<Variables>>,
 }
 
 impl Context {
@@ -19,24 +21,29 @@ impl Context {
         }
     }
 
+    /// Creates a deep copy of another context.
     pub fn with_variables_from(other: &Self) -> Self {
         Self {
             variables: Arc::new(RwLock::new(other.variables.read().unwrap().clone())),
         }
     }
 
+    /// Returns the number of variables in the context.
     pub fn variable_count(&self) -> usize {
         self.variables.read().unwrap().len()
     }
 
+    /// Returns a boolean indicating whether the context contains the variable.
     pub fn contains(&self, identifier: &Identifier) -> bool {
         self.variables.read().unwrap().contains_key(identifier)
     }
 
+    /// Returns the full VariableData and Span if the context contains the given identifier.
     pub fn get(&self, identifier: &Identifier) -> Option<(VariableData, Span)> {
         self.variables.read().unwrap().get(identifier).cloned()
     }
 
+    /// Returns the type of the variable with the given identifier.
     pub fn get_type(&self, identifier: &Identifier) -> Option<Type> {
         match self.variables.read().unwrap().get(identifier) {
             Some((VariableData::Type(r#type), _)) => Some(r#type.clone()),
@@ -45,6 +52,7 @@ impl Context {
         }
     }
 
+    /// Returns the VariableData of the variable with the given identifier.
     pub fn get_variable_data(&self, identifier: &Identifier) -> Option<VariableData> {
         match self.variables.read().unwrap().get(identifier) {
             Some((variable_data, _)) => Some(variable_data.clone()),
@@ -52,6 +60,7 @@ impl Context {
         }
     }
 
+    /// Returns the value of the variable with the given identifier.
     pub fn get_value(&self, identifier: &Identifier) -> Option<Value> {
         match self.variables.read().unwrap().get(identifier) {
             Some((VariableData::Value(value), _)) => Some(value.clone()),
@@ -59,6 +68,7 @@ impl Context {
         }
     }
 
+    /// Sets a variable to a type, with a position given for garbage collection.
     pub fn set_type(&self, identifier: Identifier, r#type: Type, position: Span) {
         log::trace!("Setting {identifier} to type {type} at {position:?}");
 
@@ -68,6 +78,7 @@ impl Context {
             .insert(identifier, (VariableData::Type(r#type), position));
     }
 
+    /// Sets a variable to a value.
     pub fn set_value(&self, identifier: Identifier, value: Value) {
         log::trace!("Setting {identifier} to value {value}");
 
@@ -81,6 +92,7 @@ impl Context {
         variables.insert(identifier, (VariableData::Value(value), last_position));
     }
 
+    /// Collects garbage up to the given position, removing all variables with lesser positions.
     pub fn collect_garbage(&self, current_position: usize) {
         log::trace!("Collecting garbage up to {current_position}");
 
@@ -98,6 +110,8 @@ impl Context {
         variables.shrink_to_fit();
     }
 
+    /// Updates a variable's last known position, allowing it to live longer in the program.
+    /// Returns a boolean indicating whether the variable was found.
     pub fn update_last_position(&self, identifier: &Identifier, position: Span) -> bool {
         if let Some((_, last_position)) = self.variables.write().unwrap().get_mut(identifier) {
             *last_position = position;
@@ -109,6 +123,23 @@ impl Context {
             false
         }
     }
+
+    /// Recovers the context from a poisoned state by recovering data from an error.
+    ///
+    /// This method is not used. The context's other methods do not return poison errors because
+    /// they are infallible.
+    pub fn _recover_from_poison(&mut self, error: &ContextPoisonError) {
+        log::debug!("Context is recovering from poison error");
+
+        let recovered = error.get_ref();
+        let mut new_variables = HashMap::new();
+
+        for (identifier, (variable_data, position)) in recovered.iter() {
+            new_variables.insert(identifier.clone(), (variable_data.clone(), *position));
+        }
+
+        self.variables = Arc::new(RwLock::new(new_variables));
+    }
 }
 
 impl Default for Context {
@@ -123,6 +154,8 @@ pub enum VariableData {
     Type(Type),
 }
 
+pub type ContextPoisonError<'err> = StdPoisonError<RwLockWriteGuard<'err, Variables>>;
+
 #[cfg(test)]
 mod tests {
     use crate::vm::run_with_context;

dust-lang/src/identifier.rs

@@ -62,9 +62,15 @@ impl Identifier {
     }
 }
 
+impl From<String> for Identifier {
+    fn from(string: String) -> Self {
+        Identifier::new(string)
+    }
+}
+
 impl From<&str> for Identifier {
-    fn from(text: &str) -> Self {
-        Identifier::new(text)
+    fn from(slice: &str) -> Self {
+        Identifier::new(slice)
     }
 }