[AST] Fix assertion hit in AutoClosureExpr::getUnwrappedCurryThunkExpr()

For DoubleCurryThunk cases it’s expecting an ApplyExpr directly within the
OpenExistentialExpr, but in some cases it contains an ErasureExpr (implicit
conversion) that wraps the ApplyExpr. This updates the method to look
through implicit conversions.

Resolves rdar://problem/61885996

Author: Nathan Hawes

lib/AST/Expr.cpp

@@ -1897,6 +1897,8 @@ Expr *AutoClosureExpr::getUnwrappedCurryThunkExpr() const {
 
       if (auto *openExistential = dyn_cast<OpenExistentialExpr>(innerBody)) {
         innerBody = openExistential->getSubExpr();
+        if (auto *ICE = dyn_cast<ImplicitConversionExpr>(innerBody))
+          innerBody = ICE->getSyntacticSubExpr();
       }
 
       if (auto *outerCall = dyn_cast<ApplyExpr>(innerBody)) {

test/Index/roles.swift

@@ -520,3 +520,14 @@ func useDefaultInits() {
   // CHECK: [[@LINE-1]]:15 | instance-property/Swift | y | s:14swift_ide_test7BStructV1ySbvp | Ref,RelCont
   // CHECK: [[@LINE-2]]:7 | constructor/Swift | init(x:y:z:) | s:14swift_ide_test7BStructV1x1y1zACSi_SbSStcfc | Ref,Call,RelCall,RelCont | rel: 1
 }
+
+internal protocol FromInt {
+    init(_ uint64: Int)
+}
+extension Int: FromInt { }
+func test<M>(_: M, value: Int?) {
+    if let idType = M.self as? FromInt.Type {
+        _ = value.flatMap(idType.init) as? M
+// CHECK: [[@LINE-1]]:34 | constructor/Swift | init(_:) | s:14swift_ide_test7FromIntPyxSicfc | Ref,RelCont | rel: 1
+    }
+}