resolver: Improve block scoping with a scope guard

libconlang/src/resolver.rs

@@ -3,9 +3,50 @@
 //! This will hopefully become a fully fledged static resolution pass in the future
 use std::collections::HashMap;
 
-#[allow(unused_imports)]
 use crate::ast::preamble::*;
 
+use scopeguard::Scoped;
+pub mod scopeguard {
+    //! Implements a generic RAII scope-guard
+
+    use std::ops::{Deref, DerefMut};
+
+    pub trait Scoped: Sized {
+        fn frame(&mut self) -> Guard<Self> {
+            Guard::new(self)
+        }
+        ///
+        fn enter_scope(&mut self);
+        fn exit_scope(&mut self);
+    }
+
+    pub struct Guard<'scope, T: Scoped> {
+        inner: &'scope mut T,
+    }
+    impl<'scope, T: Scoped> Guard<'scope, T> {
+        pub fn new(inner: &'scope mut T) -> Self {
+            inner.enter_scope();
+            Self { inner }
+        }
+    }
+    impl<'scope, T: Scoped> Deref for Guard<'scope, T> {
+        type Target = T;
+        fn deref(&self) -> &Self::Target {
+            self.inner
+        }
+    }
+    impl<'scope, T: Scoped> DerefMut for Guard<'scope, T> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.inner
+        }
+    }
+    impl<'scope, T: Scoped> Drop for Guard<'scope, T> {
+        fn drop(&mut self) {
+            self.inner.exit_scope()
+        }
+    }
+}
+
 /// Prints like [println] if `debug_assertions` are enabled
 macro debugln($($t:tt)*) {
     if cfg!(debug_assertions) {
@@ -309,11 +350,20 @@ pub struct Resolver {
     types: Vec<Type>,
 }
 
+impl Scoped for Resolver {
+    fn enter_scope(&mut self) {
+        self.enter_scope();
+    }
+    fn exit_scope(&mut self) {
+        self.exit_scope();
+    }
+}
+
 impl Default for Resolver {
     fn default() -> Self {
         let mut new = Self {
             count: Default::default(),
-            scopes: Default::default(),
+            scopes: vec![Default::default()],
             modules: Default::default(),
             module: Default::default(),
             types: Default::default(),
@@ -419,16 +469,6 @@ impl Resolver {
         self.get_mut(name)?.assign(name, ty)
     }
 }
-/// Manages a sub-function lexical scope
-/// ```rust,ignore
-/// macro scope(self, inner: {...}) -> Result<_, Error>
-/// ```
-macro scope($self:ident, $inner:tt ) {{
-    $self.enter_scope();
-    let scope = (|| $inner)();
-    $self.exit_scope();
-    scope
-}}
 /// Manages a module scope
 /// ```rust,ignore
 /// macro module(self, name: &str, inner: {...}) -> Result<_, Error>
@@ -508,17 +548,16 @@ impl Resolve for FnDecl {
         // create a new lexical scope
         let scopes = std::mem::take(&mut resolver.scopes);
         // type-check the function body
-        let out = scope!(resolver, {
+        let out = {
+            let mut resolver = resolver.frame();
             let mut evaluated_args = vec![];
             for arg in args {
-                evaluated_args.push(arg.resolve(resolver)?)
+                evaluated_args.push(arg.resolve(&mut resolver)?)
             }
-            // TODO: proper typing for return addresses
             let fn_decl = Type::Fn { args: evaluated_args.clone(), ret: Box::new(Type::Empty) };
             resolver.get_mut(name)?.assign(name, &fn_decl)?;
-            // Enter the new module
-            module!(resolver, name, { body.resolve(resolver) })
-        });
+            module!(resolver, name, { body.resolve(&mut resolver) })
+        };
         let _ = std::mem::replace(&mut resolver.scopes, scopes);
         out
     }
@@ -531,12 +570,11 @@ impl Resolve for Name {
 impl Resolve for Block {
     fn resolve(&mut self, resolver: &mut Resolver) -> TyResult<Type> {
         let Block { let_count: _, statements, expr } = self;
-        scope!(resolver, {
+        let mut resolver = resolver.frame();
         for stmt in statements {
-                stmt.resolve(resolver)?;
+            stmt.resolve(&mut resolver)?;
         }
-            expr.resolve(resolver)
-        })
+        expr.resolve(&mut resolver)
     }
 }
 impl Resolve for Expr {
@@ -774,12 +812,13 @@ impl Resolve for For {
             Type::Range(t) => t,
             got => Err(Error::TypeMismatch { want: Type::Range(Type::Inferred.into()), got })?,
         };
-        let body_ty = scope!(resolver, {
+        let body_ty = {
+            let mut resolver = resolver.frame();
             // bind the variable in the loop scope
             *index = Some(resolver.insert_scope(name, false)?);
             resolver.get_mut(name)?.assign(name, &ty)?;
-            body.resolve(resolver)
-        })?;
+            body.resolve(&mut resolver)
+        }?;
         // visit the else block
         let else_ty = else_.resolve(resolver)?;
         if body_ty != else_ty {