Add tuple type variable decleration

crates/parser/src/ast/statement.rs

@@ -46,6 +46,7 @@ pub struct MatchItem(pub Vec<Pattern>, pub Expression);
 pub struct VarDecl {
     pub type_: Option<TypeExpr>,
     pub name: Pattern,
+    pub true_type: bool,
     pub tuple_names: Vec<Pattern>,
 }
 

crates/parser/src/grammar.pest

@@ -225,9 +225,11 @@ attributes = {
 // ======================================================
 // DECLARATION HELPERS
 // ======================================================
+as_kw = { "as" }
+
 var_decl = {
     ("let" ~ pattern ~ ("," ~ pattern)*)
-  | type_expr ~ (!tuple_pattern ~ pattern ~ ("," ~ pattern)*)
+  | type_expr ~ as_kw? ~ (!tuple_pattern ~ pattern ~ ("," ~ pattern)*)
 }
 
 field = {

crates/parser/src/parser/common/decl.rs

@@ -2,7 +2,7 @@ use crate::{
     Rule,
     ast::*,
     error::{AstError, collect_recovered},
-    parser::consume_rule,
+    parser::{consume_rule, listen_rule},
 };
 
 impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for VarDeclStmt {
@@ -55,6 +55,7 @@ impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for VarDecl {
                     type_: consume_rule(&mut inner, Rule::type_expr)
                         .map(TypeExpr::try_from)
                         .transpose()?,
+                    true_type: listen_rule(&mut inner, Rule::as_kw),
                     name: Pattern::try_from(inner.next().unwrap())?,
                     tuple_names: collect_recovered(inner)?,
                 })