fix diverse

handrolled_parser/core.mbt

@@ -121,6 +121,11 @@ fn State::loc_start_with(state : Self, start : Position) -> Location {
   { start, end: state.parsed_position }
 }
 
+///|
+fn State::empty_loc(state : Self) -> Location {
+  { start: state.parsed_position, end: state.parsed_position }
+}
+
 ///|
 fn State::peek_location(state : Self) -> Location {
   let (_, start, end) = state.peek()

handrolled_parser/parse_expr_test.mbt

@@ -290,7 +290,7 @@ test {
             "loc": {
               "file": "",
               "start": { "line": 2, "column": 4 },
-              "end": { "line": 2, "column": 8 },
+              "end": { "line": 4, "column": 5 },
             },
             "children": {
               "pattern": {
@@ -318,7 +318,7 @@ test {
                 "loc": {
                   "file": "",
                   "start": { "line": 2, "column": 9 },
-                  "end": { "line": 2, "column": 8 },
+                  "end": { "line": 4, "column": 5 },
                 },
                 "children": {
                   "expr": {
@@ -432,7 +432,7 @@ test {
                     "loc": {
                       "file": "",
                       "start": { "line": 2, "column": 9 },
-                      "end": { "line": 2, "column": 8 },
+                      "end": { "line": 4, "column": 5 },
                     },
                     "children": {},
                   },

handrolled_parser/parser.mbt

@@ -443,7 +443,10 @@ fn State::parse_fun_decl(
     )
     |> @list.from_array
   })
-  let params_loc = self.loc_start_with(param_loc_start)
+  let params_loc = match decl_params {
+    Some(_) => self.loc_start_with(param_loc_start)
+    None => self.empty_loc()
+  }
   let (return_type, error_type) = self.parse_func_return_type()
   let loc = self.loc_start_with(spos)
   {
@@ -4259,8 +4262,8 @@ fn State::parse_simple_expr(
               self.parse_semi_trailing_record()
             COLON | COMMA | RBRACE => self.parse_record_expr(type_name=None)
             _ => {
-              let loc = self.loc_start_with(spos)
               let expr = self.parse_block_expr()
+              let loc = self.loc_start_with(spos)
               Group(expr~, group=Brace, loc~)
             }
           }
@@ -4276,8 +4279,8 @@ fn State::parse_simple_expr(
         | BYTES(_)
         | STRING(_) if self.peek_token(nth=2) is COLON => self.parse_map_expr()
         _ => {
-          let loc = self.loc_start_with(spos)
           let expr = self.parse_block_expr()
+          let loc = self.loc_start_with(spos)
           Group(expr~, group=Brace, loc~)
         }
       }

test/sync_test/loc_regression_test.mbt

@@ -0,0 +1,60 @@
+///|
+let loc_regression_source =
+  #| let global: Int = {
+  #|   1
+  #| }
+  #|
+  #| fn init {
+  #|   let _ = global
+  #| }
+
+///|
+fn parse_loc_regression(
+  parser : @parser.Parser,
+) -> (@syntax.Impls, @basic.Location, @basic.Location, Json) raise Error {
+  let (impls, diagnostics) = @parser.parse_string(
+    loc_regression_source,
+    name="loc_regression.mbt",
+    parser~,
+  )
+  if !diagnostics.is_empty() {
+    fail(diagnostics.to_string())
+  }
+  let mut brace_group_loc = None
+  let mut params_loc = None
+  for impl_ in impls {
+    match impl_ {
+      TopLetDef(expr=Group(group=Brace, loc~, ..), ..) =>
+        brace_group_loc = Some(loc)
+      TopFuncDef(fun_decl~, ..) => params_loc = Some(fun_decl.params_loc)
+      _ => ()
+    }
+  }
+  let json = @basic.show_loc.protect(@basic.String, fn() {
+    impls.map(impl_ => impl_.json_repr()).to_json()
+  })
+  match (brace_group_loc, params_loc) {
+    (Some(brace_group_loc), Some(params_loc)) =>
+      (impls, brace_group_loc, params_loc, json)
+    _ => fail("failed to find loc regression fixtures in parsed AST")
+  }
+}
+
+///|
+test "loc parity for brace group and empty fn params" {
+  let (_, hand_group_loc, hand_params_loc, hand_json) = parse_loc_regression(
+    @parser.Handrolled,
+  )
+  let (_, yacc_group_loc, yacc_params_loc, yacc_json) = parse_loc_regression(
+    @parser.MoonYacc,
+  )
+  inspect(hand_group_loc, content="loc_regression.mbt-1:20-3:3")
+  inspect(hand_params_loc, content="loc_regression.mbt-5:9-5:9")
+  inspect(yacc_group_loc, content="loc_regression.mbt-1:20-3:3")
+  inspect(yacc_params_loc, content="loc_regression.mbt-5:9-5:9")
+  if hand_json != yacc_json {
+    fail(
+      "loc-sensitive AST mismatch between handrolled and yacc parsers.\nhandrolled:\n\{hand_json.stringify(indent=2)}\n\nyacc:\n\{yacc_json.stringify(indent=2)}",
+    )
+  }
+}