Type aliases

crates/parser/src/ast/top_level.rs

@@ -32,6 +32,11 @@ pub enum TopLevelKind {
     ImplDecl(ImplDecl),
     StaticDecl(VarDeclStmt),
     ConstDecl(VarDeclStmt),
+    TypeAlias {
+        name: Identifier,
+        generics: Option<GenericsDecl>,
+        ty: TypeExpr,
+    },
     TraitDecl {
         visibility: Visibility,
         name: Identifier,

crates/parser/src/grammar.pest

@@ -35,6 +35,7 @@ keyword = {
   | "unsafe"
   | "override"
   | "const"
+  | "type"
 }
 
 identifier = @{
@@ -369,13 +370,18 @@ function_decl = {
 const_decl  = { "const" ~ var_decl_statement ~ ";" }
 static_decl = { "static" ~ var_decl_statement ~ ";" }
 
+// ======================================================
+// Type aliases
+// ======================================================
+type_alias = { "type" ~ identifier ~ generics_decl? ~ "=" ~ type_expr ~ ";" }
+
 // ======================================================
 // TOP LEVEL
 // ======================================================
 
 top_level = {
     mod_attribute
-  | (attributes ~ (import | impl_for_decl | impl_decl | trait_decl | struct_decl | enum_decl | class_decl | declare_module | function_decl | const_decl | static_decl))
+  | (attributes ~ (import | impl_for_decl | impl_decl | trait_decl | struct_decl | enum_decl | class_decl | declare_module | function_decl | const_decl | static_decl | type_alias))
 }
 
 // ======================================================

crates/parser/src/parser/items/mod.rs

@@ -125,6 +125,14 @@ impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for TopLevelKind {
             Rule::const_decl => Ok(TopLevelKind::ConstDecl(inner.next().unwrap().try_into()?)),
             Rule::static_decl => Ok(TopLevelKind::StaticDecl(inner.next().unwrap().try_into()?)),
 
+            Rule::type_alias => Ok(TopLevelKind::TypeAlias {
+                name: inner.next().unwrap().try_into()?,
+                generics: consume_rule(&mut inner, Rule::generics_decl)
+                    .map(GenericsDecl::try_from)
+                    .transpose()?,
+                ty: inner.next().unwrap().try_into()?,
+            }),
+
             _ => AstError::bug_unimplemented(pair),
         }
     }