[flang] Fix bogus error from assignment to CLASS(*)

[klausler]

Summary

Assignment semantics was coughing up bad errors and crashes for
intrinsic assignments to unlimited polymorphic entities while
looking for any (impossible) user defined ASSIGNMENT(=) generic
or intrinsic type conversion.

[vdonaldson]

c'est bon

flang/lib/Semantics/expression.cpp

const Symbol *ArgumentAnalyzer::FindBoundOp(
   }
   return pair.first;
 }
 
 // If there is an implicit conversion between intrinsic types, make it explicit
 void ArgumentAnalyzer::AddAssignmentConversion(
     const DynamicType &lhsType, const DynamicType &rhsType) {
   if (lhsType.category() == rhsType.category() &&
-      lhsType.kind() == rhsType.kind()) {
+      (lhsType.category() == TypeCategory::Derived ||
+          lhsType.kind() == rhsType.kind())) {
     // no conversion necessary
   } else if (auto rhsExpr{evaluate::ConvertToType(lhsType, MoveExpr(1))}) {
     std::optional<parser::CharBlock> source;
     if (actuals_[1]) {
       source = actuals_[1]->sourceLocation();
     }
     actuals_[1] = ActualArgument{*rhsExpr};
     SetArgSourceLocation(actuals_[1], source);
if (actuals_.size() == 1) {
     }
   }
 }
 
 std::string ArgumentAnalyzer::TypeAsFortran(std::size_t i) {
   if (i >= actuals_.size() || !actuals_[i]) {
     return "missing argument";
   } else if (std::optional<DynamicType> type{GetType(i)}) {
-    return type->category() == TypeCategory::Derived
+    return type->IsAssumedType()         ? "TYPE(*)"s
+        : type->IsUnlimitedPolymorphic() ? "CLASS(*)"s
+        : type->IsPolymorphic()          ? "CLASS("s + type->AsFortran() + ')'
+        : type->category() == TypeCategory::Derived
         ? "TYPE("s + type->AsFortran() + ')'
         : type->category() == TypeCategory::Character
         ? "CHARACTER(KIND="s + std::to_string(type->kind()) + ')'
         : ToUpperCase(type->AsFortran());
   } else {
     return "untyped";
   }
 }

flang/lib/Semantics/tools.cpp

 }
 
 Tristate IsDefinedAssignment(
     const std::optional<evaluate::DynamicType> &lhsType, int lhsRank,
     const std::optional<evaluate::DynamicType> &rhsType, int rhsRank) {
   if (!lhsType || !rhsType) {
     return Tristate::No; // error or rhs is untyped
   }
+  if (lhsType->IsUnlimitedPolymorphic() || rhsType->IsUnlimitedPolymorphic()) {
+    return Tristate::No;
+  }
   TypeCategory lhsCat{lhsType->category()};
   TypeCategory rhsCat{rhsType->category()};
   if (rhsRank > 0 && lhsRank != rhsRank) {
     return Tristate::Yes;
   } else if (lhsCat != TypeCategory::Derived) {
     return ToTristate(lhsCat != rhsCat &&
         (!IsNumericTypeCategory(lhsCat) || !IsNumericTypeCategory(rhsCat)));
   } else if (MightBeSameDerivedType(lhsType, rhsType)) {

flang/test/Semantics/resolve63.f90

contains
   end
   subroutine test(x, y, z)
     class(t1) :: x
     class(t2) :: y
     integer :: i
     i = x + y
     i = x + i
     i = y + i
-    !ERROR: No intrinsic or user-defined OPERATOR(+) matches operand types TYPE(t2) and TYPE(t1)
+    !ERROR: No intrinsic or user-defined OPERATOR(+) matches operand types CLASS(t2) and CLASS(t1)
     i = y + x
-    !ERROR: No intrinsic or user-defined OPERATOR(+) matches operand types INTEGER(4) and TYPE(t1)
+    !ERROR: No intrinsic or user-defined OPERATOR(+) matches operand types INTEGER(4) and CLASS(t1)
     i = i + x
   end
 end
 
 ! Some cases where NULL is acceptable - ensure no false errors
 module m7
   implicit none
   type :: t1
subroutine test
     call generic(null(), rp) ! ok
     call generic(null(), ip) ! ok
     call generic(null(mold=ip), null()) ! ok
     call generic(null(), null(mold=ip)) ! ok
     !ERROR: One or more NULL() actual arguments to the generic procedure 'generic' requires a MOLD= for disambiguation
     call generic(null(), null())
   end subroutine
 end
+
+! Ensure no bogus errors for assignments to CLASS(*) allocatable
+module m10
+  type :: t1
+    integer :: n
+  end type
+ contains
+  subroutine test
+    class(*), allocatable :: poly
+    poly = 1
+    poly = 3.14159
+    poly = 'Il faut imaginer Sisyphe heureux'
+    poly = t1(1)
+  end subroutine
+end module

flang/test/Semantics/selecttype03.f90

else
       fun => NULL()
     end if
   end function
 
   function foo(i)
     integer :: i
     class(t1),DIMENSION(:),allocatable :: foo
     integer, dimension(2) :: U
-    U = (/ 1,2 /)  
+    U = (/ 1,2 /)
     if (i>0) then
       foo = array1(2,U)
     else if (i<0) then
-      !ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches operand types TYPE(t1) and TYPE(t2)
+      !ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches operand types CLASS(t1) and CLASS(t2)
       foo = array2(2,U)
     end if
   end function
 
   subroutine sub_with_in_and_inout_param(y, z)
     type(t2), INTENT(IN) :: y
     class(t2), INTENT(INOUT) :: z
     z%i = 10