error properly on unknown label instead of crash

src/typecheck.ml

@@ -64,7 +64,10 @@ module Env = struct
       let (Bt_raw ((None | Some _), t)) = t.desc in
       t
 
-  let block_type_get i env = List.nth env.blocks i
+  let block_type_get i env =
+    match List.nth_opt env.blocks i with
+    | None -> Format.ksprintf Result.error "unknown label %d" i
+    | Some bt -> Ok bt
 
   let table_type_get_from_module i (modul : Simplified.modul) =
     let value = Indexed.get_at_exn i modul.table.values in
@@ -442,22 +445,22 @@ let rec typecheck_instr (env : env) (stack : stack) (instr : simplified instr) :
     if not @@ Hashtbl.mem env.refs i then Error "undeclared function reference"
     else Stack.push [ Ref_type Func_ht ] stack
   | Br (Raw i) ->
-    let jt = Env.block_type_get i env in
+    let* jt = Env.block_type_get i env in
     let* _stack = Stack.pop jt stack in
     Ok [ any ]
   | Br_if (Raw i) ->
     let* stack = Stack.pop [ i32 ] stack in
-    let jt = Env.block_type_get i env in
+    let* jt = Env.block_type_get i env in
     let* stack = Stack.pop jt stack in
     Stack.push jt stack
   | Br_table (branches, Raw i) ->
     let* stack = Stack.pop [ i32 ] stack in
-    let default_jt = Env.block_type_get i env in
+    let* default_jt = Env.block_type_get i env in
     let* _stack = Stack.pop default_jt stack in
     let* () =
       array_iter
         (fun (Raw i : simplified indice) ->
-          let jt = Env.block_type_get i env in
+          let* jt = Env.block_type_get i env in
           if not (List.length jt = List.length default_jt) then
             Error "type mismatch (br table)"
           else

test/script/gc.t

@@ -12,11 +12,11 @@
   [1]
   $ dune exec owi -- script --no-exhaustion gc/extern.wast
   owi: internal error, uncaught exception:
-       File "src/typecheck.ml", line 493, characters 4-10: Assertion failed
-       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 493, characters 4-16
+       File "src/typecheck.ml", line 496, characters 4-10: Assertion failed
+       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 496, characters 4-16
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
-       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 505, characters 15-59
-       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 527, characters 6-112
+       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 508, characters 15-59
+       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 530, characters 6-112
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
        Called from Owi__Compile.until_typecheck in file "src/compile.ml", line 28, characters 14-31
        Called from Owi__Compile.until_optimize in file "src/compile.ml", line 32, characters 11-36
@@ -49,11 +49,11 @@
   [125]
   $ dune exec owi -- script --no-exhaustion gc/ref_cast.wast
   owi: internal error, uncaught exception:
-       File "src/typecheck.ml", line 493, characters 4-10: Assertion failed
-       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 493, characters 4-16
+       File "src/typecheck.ml", line 496, characters 4-10: Assertion failed
+       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 496, characters 4-16
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
-       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 505, characters 15-59
-       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 527, characters 6-112
+       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 508, characters 15-59
+       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 530, characters 6-112
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
        Called from Owi__Compile.until_typecheck in file "src/compile.ml", line 28, characters 14-31
        Called from Owi__Compile.until_optimize in file "src/compile.ml", line 32, characters 11-36
@@ -71,11 +71,11 @@
   [125]
   $ dune exec owi -- script --no-exhaustion gc/ref_eq.wast
   owi: internal error, uncaught exception:
-       File "src/typecheck.ml", line 493, characters 4-10: Assertion failed
-       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 493, characters 4-16
+       File "src/typecheck.ml", line 496, characters 4-10: Assertion failed
+       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 496, characters 4-16
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
-       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 505, characters 15-59
-       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 527, characters 6-112
+       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 508, characters 15-59
+       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 530, characters 6-112
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
        Called from Owi__Compile.until_typecheck in file "src/compile.ml", line 28, characters 14-31
        Called from Owi__Compile.until_optimize in file "src/compile.ml", line 32, characters 11-36
@@ -93,11 +93,11 @@
   [125]
   $ dune exec owi -- script --no-exhaustion gc/ref_test.wast
   owi: internal error, uncaught exception:
-       File "src/typecheck.ml", line 493, characters 4-10: Assertion failed
-       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 493, characters 4-16
+       File "src/typecheck.ml", line 496, characters 4-10: Assertion failed
+       Raised at Owi__Typecheck.typecheck_instr in file "src/typecheck.ml", line 496, characters 4-16
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
-       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 505, characters 15-59
-       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 527, characters 6-112
+       Called from Owi__Typecheck.typecheck_expr in file "src/typecheck.ml", line 508, characters 15-59
+       Called from Owi__Typecheck.typecheck_function in file "src/typecheck.ml", line 530, characters 6-112
        Called from Stdlib__List.fold_left in file "list.ml", line 123, characters 24-34
        Called from Owi__Compile.until_typecheck in file "src/compile.ml", line 28, characters 14-31
        Called from Owi__Compile.until_optimize in file "src/compile.ml", line 32, characters 11-36

test/validate/dune

@@ -1,2 +1,2 @@
 (cram
- (deps %{bin:owi}))
+ (deps %{bin:owi} unknown_label.wat))

test/validate/unknown_label.t

@@ -0,0 +1,3 @@
+  $ dune exec owi -- validate ./unknown_label.wat
+  unknown label 2
+  [1]

test/validate/unknown_label.wat

@@ -0,0 +1,15 @@
+(module
+  (func $f
+    (loop
+      br 0
+      br 1
+      br 2
+      (loop
+        br 0
+        br 1
+        br 2
+        br 3
+        br 4
+      )
+    )
+  ))