[flang][hlfir] Support type descriptor for initialized character component

These compiler generated component descriptor include designators packaged
as CLASS(*) for simplicity. HLFIR hit an assert in an std::get trying to
recover an Expr<SomeChar> while translating the expression type.
Use the dynamic type of the CLASS(*) expr in that case to recover the
compiler length.

Differential Revision: https://reviews.llvm.org/D144960

1 files changed, 16 insertions, 5 deletions

diff --git a/flang/lib/Lower/ConvertType.cpp b/flang/lib/Lower/ConvertType.cpp
index 4fab5a5..d701749 100644
--- a/flang/lib/Lower/ConvertType.cpp
+++ b/flang/lib/Lower/ConvertType.cpp
@@ -433,11 +433,22 @@ struct TypeBuilderImpl {
     // Do not use dynamic type length here. We would miss constant
     // lengths opportunities because dynamic type only has the length
     // if it comes from a declaration.
-    auto charExpr =
-        std::get<Fortran::evaluate::Expr<Fortran::evaluate::SomeCharacter>>(
-            expr.u);
-    if (auto constantLen = toInt64(charExpr.LEN()))
-      return *constantLen;
+    if (const auto *charExpr = std::get_if<
+            Fortran::evaluate::Expr<Fortran::evaluate::SomeCharacter>>(
+            &expr.u)) {
+      if (auto constantLen = toInt64(charExpr->LEN()))
+        return *constantLen;
+    } else if (auto dynamicType = expr.GetType()) {
+      // When generating derived type type descriptor as structure constructor,
+      // semantics wraps designators to data component initialization into
+      // CLASS(*), regardless of their actual type.
+      // GetType() will recover the actual symbol type as the dynamic type, so
+      // getCharacterLength may be reached even if expr is packaged as an
+      // Expr<SomeDerived> instead of an Expr<SomeChar>.
+      // Just use the dynamic type here again to retrieve the length.
+      if (auto constantLen = toInt64(dynamicType->GetCharLength()))
+        return *constantLen;
+    }
     return fir::SequenceType::getUnknownExtent();
   }