Resolve alias targets (#548)

During analysis, resolve alias targets from `Name`s to `Rc<Recipe>`,
giving us type-level assurance that alias resolution was performed, and
avoiding the need to look up alias targets in a separate table when
running.

src/alias.rs

@@ -2,28 +2,39 @@ use crate::common::*;
 
 /// An alias, e.g. `name := target`
 #[derive(Debug, PartialEq)]
-pub(crate) struct Alias<'src> {
+pub(crate) struct Alias<'src, T = Rc<Recipe<'src>>> {
   pub(crate) name: Name<'src>,
-  pub(crate) target: Name<'src>,
+  pub(crate) target: T,
+}
+
+impl<'src> Alias<'src, Name<'src>> {
+  pub(crate) fn line_number(&self) -> usize {
+    self.name.line
+  }
+
+  pub(crate) fn resolve(self, target: Rc<Recipe<'src>>) -> Alias<'src> {
+    assert_eq!(self.target.lexeme(), target.name.lexeme());
+
+    Alias {
+      name: self.name,
+      target,
+    }
+  }
 }
 
 impl Alias<'_> {
   pub(crate) fn is_private(&self) -> bool {
     self.name.lexeme().starts_with('_')
   }
-
-  pub(crate) fn line_number(&self) -> usize {
-    self.name.line
-  }
 }
 
-impl<'src> Keyed<'src> for Alias<'src> {
+impl<'src, T> Keyed<'src> for Alias<'src, T> {
   fn key(&self) -> &'src str {
     self.name.lexeme()
   }
 }
 
-impl<'a> Display for Alias<'a> {
+impl<'src> Display for Alias<'src, Name<'src>> {
   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
     write!(
       f,
@@ -33,3 +44,14 @@ impl<'a> Display for Alias<'a> {
     )
   }
 }
+
+impl<'src> Display for Alias<'src> {
+  fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    write!(
+      f,
+      "alias {} := {}",
+      self.name.lexeme(),
+      self.target.name.lexeme()
+    )
+  }
+}

src/alias_resolver.rs

@@ -1,52 +0,0 @@
-use crate::common::*;
-use CompilationErrorKind::*;
-
-pub(crate) struct AliasResolver<'a, 'b>
-where
-  'a: 'b,
-{
-  aliases: &'b Table<'a, Alias<'a>>,
-  recipes: &'b Table<'a, Rc<Recipe<'a>>>,
-}
-
-impl<'a: 'b, 'b> AliasResolver<'a, 'b> {
-  pub(crate) fn resolve_aliases(
-    aliases: &Table<'a, Alias<'a>>,
-    recipes: &Table<'a, Rc<Recipe<'a>>>,
-  ) -> CompilationResult<'a, ()> {
-    let resolver = AliasResolver { aliases, recipes };
-
-    resolver.resolve()?;
-
-    Ok(())
-  }
-
-  fn resolve(&self) -> CompilationResult<'a, ()> {
-    for alias in self.aliases.values() {
-      self.resolve_alias(alias)?;
-    }
-
-    Ok(())
-  }
-
-  fn resolve_alias(&self, alias: &Alias<'a>) -> CompilationResult<'a, ()> {
-    let token = alias.name.token();
-    // Make sure the alias doesn't conflict with any recipe
-    if let Some(recipe) = self.recipes.get(alias.name.lexeme()) {
-      return Err(token.error(AliasShadowsRecipe {
-        alias: alias.name.lexeme(),
-        recipe_line: recipe.line_number(),
-      }));
-    }
-
-    // Make sure the target recipe exists
-    if self.recipes.get(alias.target.lexeme()).is_none() {
-      return Err(token.error(UnknownAliasTarget {
-        alias: alias.name.lexeme(),
-        target: alias.target.lexeme(),
-      }));
-    }
-
-    Ok(())
-  }
-}

src/analyzer.rs

@@ -5,7 +5,7 @@ use CompilationErrorKind::*;
 pub(crate) struct Analyzer<'src> {
   recipes: Table<'src, Recipe<'src, Name<'src>>>,
   assignments: Table<'src, Assignment<'src>>,
-  aliases: Table<'src, Alias<'src>>,
+  aliases: Table<'src, Alias<'src, Name<'src>>>,
   sets: Table<'src, Set<'src>>,
 }
 
@@ -51,7 +51,6 @@ impl<'src> Analyzer<'src> {
     }
 
     let assignments = self.assignments;
-    let aliases = self.aliases;
 
     AssignmentResolver::resolve_assignments(&assignments)?;
 
@@ -67,7 +66,10 @@ impl<'src> Analyzer<'src> {
       }
     }
 
-    AliasResolver::resolve_aliases(&aliases, &recipes)?;
+    let mut aliases = Table::new();
+    while let Some(alias) = self.aliases.pop() {
+      aliases.insert(Self::resolve_alias(&recipes, alias)?);
+    }
 
     let mut settings = Settings::new();
 
@@ -161,7 +163,7 @@ impl<'src> Analyzer<'src> {
     Ok(())
   }
 
-  fn analyze_alias(&self, alias: &Alias<'src>) -> CompilationResult<'src, ()> {
+  fn analyze_alias(&self, alias: &Alias<'src, Name<'src>>) -> CompilationResult<'src, ()> {
     let name = alias.name.lexeme();
 
     if let Some(original) = self.aliases.get(name) {
@@ -184,6 +186,29 @@ impl<'src> Analyzer<'src> {
 
     Ok(())
   }
+
+  fn resolve_alias(
+    recipes: &Table<'src, Rc<Recipe<'src>>>,
+    alias: Alias<'src, Name<'src>>,
+  ) -> CompilationResult<'src, Alias<'src>> {
+    let token = alias.name.token();
+    // Make sure the alias doesn't conflict with any recipe
+    if let Some(recipe) = recipes.get(alias.name.lexeme()) {
+      return Err(token.error(AliasShadowsRecipe {
+        alias: alias.name.lexeme(),
+        recipe_line: recipe.line_number(),
+      }));
+    }
+
+    // Make sure the target recipe exists
+    match recipes.get(alias.target.lexeme()) {
+      Some(target) => Ok(alias.resolve(target.clone())),
+      None => Err(token.error(UnknownAliasTarget {
+        alias: alias.name.lexeme(),
+        target: alias.target.lexeme(),
+      })),
+    }
+  }
 }
 
 #[cfg(test)]

src/common.rs

@@ -47,7 +47,7 @@ pub(crate) use crate::{
 
 // structs and enums
 pub(crate) use crate::{
-  alias::Alias, alias_resolver::AliasResolver, analyzer::Analyzer, assignment::Assignment,
+  alias::Alias, analyzer::Analyzer, assignment::Assignment,
   assignment_evaluator::AssignmentEvaluator, assignment_resolver::AssignmentResolver, color::Color,
   compilation_error::CompilationError, compilation_error_kind::CompilationErrorKind,
   compiler::Compiler, config::Config, config_error::ConfigError, count::Count,

src/config.rs

@@ -441,10 +441,10 @@ impl Config {
         continue;
       }
 
-      if !recipe_aliases.contains_key(alias.target.lexeme()) {
-        recipe_aliases.insert(alias.target.lexeme(), vec![alias.name.lexeme()]);
+      if !recipe_aliases.contains_key(alias.target.name.lexeme()) {
+        recipe_aliases.insert(alias.target.name.lexeme(), vec![alias.name.lexeme()]);
       } else {
-        let aliases = recipe_aliases.get_mut(alias.target.lexeme()).unwrap();
+        let aliases = recipe_aliases.get_mut(alias.target.name.lexeme()).unwrap();
         aliases.push(alias.name.lexeme());
       }
     }
@@ -542,7 +542,7 @@ impl Config {
 
   fn show(&self, name: &str, justfile: Justfile) -> Result<(), i32> {
     if let Some(alias) = justfile.get_alias(name) {
-      let recipe = justfile.get_recipe(alias.target.lexeme()).unwrap();
+      let recipe = justfile.get_recipe(alias.target.name.lexeme()).unwrap();
       println!("{}", alias);
       println!("{}", recipe);
       Ok(())

src/item.rs

@@ -3,7 +3,7 @@ use crate::common::*;
 /// A single top-level item
 #[derive(Debug)]
 pub(crate) enum Item<'src> {
-  Alias(Alias<'src>),
+  Alias(Alias<'src, Name<'src>>),
   Assignment(Assignment<'src>),
   Recipe(Recipe<'src, Name<'src>>),
   Set(Set<'src>),

src/justfile.rs

@@ -4,7 +4,7 @@ use crate::common::*;
 pub(crate) struct Justfile<'src> {
   pub(crate) recipes: Table<'src, Rc<Recipe<'src>>>,
   pub(crate) assignments: Table<'src, Assignment<'src>>,
-  pub(crate) aliases: Table<'src, Alias<'src>>,
+  pub(crate) aliases: Table<'src, Alias<'src, Rc<Recipe<'src>>>>,
   pub(crate) settings: Settings<'src>,
   pub(crate) warnings: Vec<Warning<'src>>,
 }
@@ -166,7 +166,7 @@ impl<'src> Justfile<'src> {
     if let Some(recipe) = self.recipes.get(name) {
       Some(recipe)
     } else if let Some(alias) = self.aliases.get(name) {
-      self.recipes.get(alias.target.lexeme()).map(Rc::as_ref)
+      Some(alias.target.as_ref())
     } else {
       None
     }

src/lib.rs

@@ -16,7 +16,6 @@ pub mod node;
 pub(crate) mod fuzzing;
 
 mod alias;
-mod alias_resolver;
 mod analyzer;
 mod assignment;
 mod assignment_evaluator;

src/node.rs

@@ -26,7 +26,7 @@ impl<'src> Node<'src> for Item<'src> {
   }
 }
 
-impl<'src> Node<'src> for Alias<'src> {
+impl<'src> Node<'src> for Alias<'src, Name<'src>> {
   fn tree(&self) -> Tree<'src> {
     Tree::atom(keyword::ALIAS)
       .push(self.name.lexeme())

src/parser.rs

@@ -325,7 +325,7 @@ impl<'tokens, 'src> Parser<'tokens, 'src> {
   }
 
   /// Parse an alias, e.g `alias name := target`
-  fn parse_alias(&mut self) -> CompilationResult<'src, Alias<'src>> {
+  fn parse_alias(&mut self) -> CompilationResult<'src, Alias<'src, Name<'src>>> {
     self.presume_name(keyword::ALIAS)?;
     let name = self.parse_name()?;
     self.presume_any(&[Equals, ColonEquals])?;

src/table.rs

@@ -8,6 +8,12 @@ pub(crate) struct Table<'key, V: Keyed<'key>> {
 }
 
 impl<'key, V: Keyed<'key>> Table<'key, V> {
+  pub(crate) fn new() -> Table<'key, V> {
+    Table {
+      map: BTreeMap::new(),
+    }
+  }
+
   pub(crate) fn insert(&mut self, value: V) {
     self.map.insert(value.key(), value);
   }