Fix issue when inlining complex constants in pattern matching.

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 #### :bug: Bug Fix
 - Fix issue with GenType and `result` introduced in rc.5. https://github.com/rescript-lang/rescript-compiler/pull/6464
+- Fix compiler crash when inlining complex constants in pattern matching. https://github.com/rescript-lang/rescript-compiler/pull/6471
 
 # 11.0.0-rc.5
 

jscomp/core/lam.ml

@@ -405,10 +405,14 @@ and eq_approx_list ls ls1 = Ext_list.for_all2_no_exn ls ls1 eq_approx
 let switch lam (lam_switch : lambda_switch) : t =
   match lam with
   | Lconst (Const_int { i }) ->
-      Ext_list.assoc_by_int lam_switch.sw_consts (Int32.to_int i)
-        lam_switch.sw_failaction
+      (* Because of inlining and dead code, we might be looking at a value of unexpected type 
+         e.g. an integer, so the const case might not be found *)
+      (try
+        Ext_list.assoc_by_int lam_switch.sw_consts (Int32.to_int i) lam_switch.sw_failaction
+      with _ -> Lswitch(lam, lam_switch))
   | Lconst (Const_block (i, _, _)) ->
-      Ext_list.assoc_by_int lam_switch.sw_blocks i lam_switch.sw_failaction
+      (try Ext_list.assoc_by_int lam_switch.sw_blocks i lam_switch.sw_failaction
+      with _ -> Lswitch(lam, lam_switch))
   | _ -> Lswitch (lam, lam_switch)
 
 let stringswitch (lam : t) cases default : t =

jscomp/test/inline_condition_with_pattern_matching.res

@@ -0,0 +1,36 @@
+module Test1 = {
+  type status = Vacations(int) | Sabbatical(int) | Sick
+  type person =
+    | Teacher({age: int})
+    | Student({status: status})
+
+  let person1 = Teacher({age: 12345})
+
+  let message = switch person1 {
+  | Student({status: Vacations(_) | Sick}) => "a"
+  | _ => "b"
+  }
+}
+
+module Test2 = {
+  type status = Vacations(int) | Sabbatical(int) | Sick | Present
+  type reportCard = {passing: bool, gpa: float}
+  type person =
+    | Teacher({name: string, age: int})
+    | Student({name: string, status: status, reportCard: reportCard})
+
+  let person2 = Teacher({name: "Jane", age: 12345})
+
+  let message = switch person2 {
+  | Teacher({name: "Mary" | "Joe"}) => `Hey, still going to the party on Saturday?`
+  | Teacher({name}) =>
+    // this is matched only if `name` isn't "Mary" or "Joe"
+    `Hello ${name}.`
+  | Student({name, reportCard: {passing: true, gpa}}) =>
+    `Congrats ${name}, nice GPA of ${Js.Float.toString(gpa)} you got there!`
+  | Student({reportCard: {gpa: 0.0}, status: Vacations(daysLeft) | Sabbatical(daysLeft)}) =>
+    `Come back in ${Js.Int.toString(daysLeft)} days!`
+  | Student({status: Sick}) => `How are you feeling?`
+  | Student({name}) => `Good luck next semester ${name}!`
+  }
+}