Updated closure syntax

crates/parser/src/grammar.pest

@@ -30,7 +30,6 @@ keyword = {
   | "false"
   | "dyn"
   | "loop"
-  | "fn"
   | "unsafe"
   | "override"
 }
@@ -200,8 +199,8 @@ attributes = {
 // DECLARATION HELPERS
 // ======================================================
 var_decl = {
-    ("let" ~ pattern) |
+    ("let" ~ pattern)
-    type_expr ~ (!tuple_pattern ~ pattern)
+  | type_expr ~ (!tuple_pattern ~ pattern)
 }
 
 field = {
@@ -343,7 +342,8 @@ function_decl = {
 // ======================================================
 
 top_level = {
-    mod_attribute | (attributes ~ (import | impl_for_decl | impl_decl | trait_decl | struct_decl | enum_decl | class_decl | declare_module | function_decl))
+    mod_attribute
+  | (attributes ~ (import | impl_for_decl | impl_decl | trait_decl | struct_decl | enum_decl | class_decl | declare_module | function_decl))
 }
 
 // ======================================================
@@ -466,8 +466,8 @@ match_stmt = {
 // ------------------------------------------------------
 
 closure = {
-    "fn" ~ "(" ~ param_list ~ ")" ~ type_expr? ~ block
+    ("(" ~ param_list ~ ")" ~ "=>" ~ expr)
-  | "fn" ~ "(" ~ param_list ~ ")" ~ type_expr? ~ "->" ~ expr
+    | (type_expr ~ "(" ~ param_list ~ ")" ~ "=>" ~ expr)
 }
 
 // ------------------------------------------------------

crates/parser/src/parser/common/expr.rs

@@ -77,10 +77,10 @@ impl<'a> TryFrom<pest::iterators::Pair<'a, Rule>> for Expression {
 
             Rule::closure => {
                 ast_expr!(Expression::Closure {
-                    params: collect_recovered(inner.next().unwrap().into_inner()),
                     return_type: consume_rule(&mut inner, Rule::type_expr)
                         .map(TypeExpr::try_from)
                         .transpose(),
+                    params: collect_recovered(inner.next().unwrap().into_inner()),
                     body: Expression::try_from(inner.next().unwrap()).map(Box::new),
                 })
             }

mist-test/src/common/expr_test.mist

@@ -88,7 +88,7 @@ pub void test_as_cast() {
 }
 
 pub void test_closure() {
-    let add = fn(a, b) -> a + b;
+    let add = (a, b) => a + b;
     assert_eq!(add(2, 3), 5);
 }