[flang] Make sure allocatable components are initialzed for temp derived-type

[clementval]

Summary

Runtime functions expect clean unallocated state for descriptor. This
patch adds a call to the runtime function to initialize the temporary
derived-type created.

flang/lib/Lower/ConvertExpr.cpp

 #include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/Mangler.h"
 #include "flang/Lower/Runtime.h"
 #include "flang/Lower/Support/Utils.h"
 #include "flang/Optimizer/Builder/Character.h"
 #include "flang/Optimizer/Builder/Complex.h"
 #include "flang/Optimizer/Builder/Factory.h"
 #include "flang/Optimizer/Builder/Runtime/Character.h"
+#include "flang/Optimizer/Builder/Runtime/Derived.h"
 #include "flang/Optimizer/Builder/Runtime/RTBuilder.h"
 #include "flang/Optimizer/Builder/Runtime/Ragged.h"
 #include "flang/Optimizer/Builder/Todo.h"
 #include "flang/Optimizer/Dialect/FIRAttr.h"
 #include "flang/Optimizer/Dialect/FIRDialect.h"
 #include "flang/Optimizer/Dialect/FIROpsSupport.h"
 #include "flang/Optimizer/Support/FatalError.h"
 #include "flang/Runtime/support.h"
public:
   ExtValue genval(const Fortran::evaluate::StructureConstructor &ctor) {
     if (inInitializer)
       return genStructComponentInInitializer(ctor);
     mlir::Location loc = getLoc();
     mlir::Type ty = translateSomeExprToFIRType(converter, toEvExpr(ctor));
     auto recTy = ty.cast<fir::RecordType>();
     auto fieldTy = fir::FieldType::get(ty.getContext());
     mlir::Value res = builder.createTemporary(loc, recTy);
+    mlir::Value box = builder.createBox(loc, fir::ExtendedValue{res});
+    fir::runtime::genDerivedTypeInitialize(builder, loc, box);
 
     for (const auto &value : ctor.values()) {
       const Fortran::semantics::Symbol &sym = *value.first;
       const Fortran::lower::SomeExpr &expr = value.second.value();
       // Parent components need more work because they do not appear in the
       // fir.rec type.
       if (sym.test(Fortran::semantics::Symbol::Flag::ParentComp))
         TODO(loc, "parent component in structure constructor");

flang/test/Lower/derived-type-temp.f90

+! Test lowering of derived type temporary creation and init
+! RUN: bbc -emit-fir %s -o - | FileCheck %s
+
+program derived_temp_init
+  type t1
+    integer, allocatable :: i
+  end type
+  type t2
+    type(t1) :: c
+  end type
+  type(t1) :: x
+  type(t2) :: y
+  y = t2(x)
+end
+
+! CHECK: %[[temp:.*]] = fir.alloca !fir.type<_QFTt1{i:!fir.box<!fir.heap<i32>>}> {bindc_name = "x", uniq_name = "_QFEx"}
+! CHECK: %[[box:.*]] = fir.embox %[[temp]] : (!fir.ref<!fir.type<_QFTt1{i:!fir.box<!fir.heap<i32>>}>>) -> !fir.box<!fir.type<_QFTt1{i:!fir.box<!fir.heap<i32>>}>>
+! CHECK: %[[box_none:.*]] = fir.convert %[[box]] : (!fir.box<!fir.type<_QFTt1{i:!fir.box<!fir.heap<i32>>}>>) -> !fir.box<none>
+! CHECK: %{{.*}} = fir.call @_FortranAInitialize(%[[box_none]], %{{.*}}, %{{.*}}) : (!fir.box<none>, !fir.ref<i8>, i32) -> none