[flang] Represent unknown extent correctly in getTypeAsString

[razvanlupusoru]

Looks great!

flang/lib/Optimizer/Dialect/FIRType.cpp

if (fir::isa_trivial(ty)) {
       name << "none";
       break;
     } else if (auto charTy = mlir::dyn_cast_or_null<fir::CharacterType>(ty)) {
       name << 'c' << kindMap.getCharacterBitsize(charTy.getFKind());
       if (charTy.getLen() != fir::CharacterType::singleton())
         name << "x" << charTy.getLen();
       break;
     } else if (auto seqTy = mlir::dyn_cast_or_null<fir::SequenceType>(ty)) {
-      for (auto extent : seqTy.getShape())
+      for (auto extent : seqTy.getShape()) {
+        if (extent == fir::SequenceType::getUnknownExtent())
+          name << "?x";
+        else
           name << extent << 'x';
+      }
       ty = seqTy.getEleTy();
     } else if (auto refTy = mlir::dyn_cast_or_null<fir::ReferenceType>(ty)) {
       name << "ref_";
       ty = refTy.getEleTy();
     } else if (auto ptrTy = mlir::dyn_cast_or_null<fir::PointerType>(ty)) {
       name << "ptr_";
       ty = ptrTy.getEleTy();
     } else if (auto heapTy = mlir::dyn_cast_or_null<fir::HeapType>(ty)) {

flang/unittests/Optimizer/FIRTypesTest.cpp

TEST_F(FIRTypesTest, getTypeAsString) {
   EXPECT_EQ("class_none",
       fir::getTypeAsString(
           fir::ClassType::get(mlir::NoneType::get(&context)), *kindMap));
   auto derivedTy = fir::RecordType::get(&context, "derived");
   llvm::SmallVector<std::pair<std::string, mlir::Type>> components;
   components.emplace_back("p1", mlir::IntegerType::get(&context, 64));
   derivedTy.finalize({}, components);
   EXPECT_EQ("rec_derived", fir::getTypeAsString(derivedTy, *kindMap));
+  mlir::Type dynArrTy =
+      fir::SequenceType::get({fir::SequenceType::getUnknownExtent(),
+                                 fir::SequenceType::getUnknownExtent()},
+          ty);
+  EXPECT_EQ("?x?xi64", fir::getTypeAsString(dynArrTy, *kindMap));
 }