Index: flang/lib/Evaluate/intrinsics.cpp
===================================================================
--- flang/lib/Evaluate/intrinsics.cpp
+++ flang/lib/Evaluate/intrinsics.cpp
@@ -1067,6 +1067,16 @@
 
 static const IntrinsicInterface intrinsicSubroutine[]{
     {"abort", {}, {}, Rank::elemental, IntrinsicClass::impureSubroutine},
+    {"co_sum",
+        {{"a", AnyNumeric, Rank::anyOrAssumedRank, Optionality::required,
+             common::Intent::InOut},
+            {"result_image", AnyInt, Rank::scalar, Optionality::optional,
+                common::Intent::In},
+            {"stat", AnyInt, Rank::scalar, Optionality::optional,
+                common::Intent::Out},
+            {"errmsg", DefaultChar, Rank::scalar, Optionality::optional,
+                common::Intent::InOut}},
+        {}, Rank::elemental, IntrinsicClass::collectiveSubroutine},
     {"cpu_time",
         {{"time", AnyReal, Rank::scalar, Optionality::required,
             common::Intent::Out}},
@@ -1622,6 +1632,35 @@
     }
   }
 
+  // Check and restrict coindexed objects being passed to certain arguments
+  // in the collective subroutines and move_alloc
+  // TODO: Add rest of collective subroutines to this check as they are
+  // added to the list of intrinsic subroutines
+  if (std::strcmp(name, "move_alloc") == 0 ||
+      std::strcmp(name, "co_sum") == 0) {
+    for (std::size_t j{0}; j < dummies; ++j) {
+      const ActualArgument *arg{actualForDummy[j]};
+      if (arg) {
+        const IntrinsicDummyArgument &d{
+            dummy[std::min(j, dummyArgPatterns - 1)]};
+        const char *dummyName(d.keyword);
+        if (std::strcmp(dummyName, "a") == 0 ||
+            std::strcmp(dummyName, "stat") == 0 ||
+            std::strcmp(dummyName, "errmsg") == 0 ||
+            std::strcmp(dummyName, "from") == 0 ||
+            std::strcmp(dummyName, "to") == 0) {
+          if (const auto *expr{arg->UnwrapExpr()}) {
+            if (ExtractCoarrayRef(*expr)) {
+              context.messages().Say(arg->sourceLocation(),
+                  "'%s' argument to '%s' may not be a coindexed object"_err_en_US,
+                  dummyName, name);
+            }
+          }
+        }
+      }
+    }
+  }
+
   // Calculate the characteristics of the function result, if any
   std::optional<DynamicType> resultType;
   if (auto category{result.categorySet.LeastElement()}) {
Index: flang/test/Semantics/collectives01.f90
===================================================================
--- flang/test/Semantics/collectives01.f90
+++ flang/test/Semantics/collectives01.f90
@@ -1,8 +1,6 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1
-! XFAIL: *
 ! This test checks for semantic errors in co_sum subroutine calls based on
 ! the co_reduce interface defined in section 16.9.50 of the Fortran 2018 standard.
-! To Do: add co_sum to the list of intrinsics
 
 program test_co_sum
   implicit none
@@ -52,6 +50,9 @@
   !ERROR: missing mandatory 'a=' argument
   call co_sum(result_image=1, stat=status, errmsg=message)
 
+  !ERROR: repeated keyword argument to intrinsic 'co_sum'
+  call co_sum(a=i, a=c)
+
   ! argument 'a' shall be of numeric type
   !ERROR: Actual argument for 'a=' has bad type 'LOGICAL(4)'
   call co_sum(bool)
@@ -60,8 +61,7 @@
   !ERROR: Actual argument associated with INTENT(IN OUT) dummy argument 'a=' must be definable
   call co_sum(a=1+1)
   
-  ! argument 'a' shall not be a coindexed object
-  !ERROR: to be determined
+  !ERROR: 'a' argument to 'co_sum' may not be a coindexed object
   call co_sum(a=coindexed_real[1])
   
   ! 'result_image' argument shall be a integer
@@ -76,8 +76,7 @@
   !ERROR: Actual argument associated with INTENT(OUT) dummy argument 'stat=' must be definable
   call co_sum(a=i, result_image=1, stat=1+1, errmsg=message)
 
-  ! 'stat' argument shall be noncoindexed
-  !ERROR: to be determined
+  !ERROR: 'stat' argument to 'co_sum' may not be a coindexed object
   call co_sum(d, stat=coindexed_integer[1])
  
   ! 'stat' argument shall be an integer
@@ -92,8 +91,7 @@
   !ERROR: Actual argument associated with INTENT(IN OUT) dummy argument 'errmsg=' must be definable
   call co_sum(a=i, result_image=1, stat=status, errmsg='c')
   
-  ! 'errmsg' argument shall be noncoindexed
-  !ERROR: to be determined
+  !ERROR: 'errmsg' argument to 'co_sum' may not be a coindexed object
   call co_sum(c, errmsg=coindexed_character[1])
  
   ! 'errmsg' argument shall be character scalar
Index: flang/test/Semantics/move_alloc.f90
===================================================================
--- /dev/null
+++ flang/test/Semantics/move_alloc.f90
@@ -0,0 +1,31 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+! Check for semantic errors in move_alloc() subroutine calls
+program main
+  integer, allocatable :: a(:)[:], b(:)[:], c(:)[:], d(:)[:]
+  !ERROR: 'e' is an ALLOCATABLE coarray and must have a deferred coshape
+  integer, allocatable :: e(:)[*]
+  integer status, coindexed_status[*]
+  character(len=1) message, coindexed_message[*]
+
+  ! standards conforming
+  allocate(a(3)[*])
+  a = [ 1, 2, 3 ]
+  call move_alloc(a, b, status, message)
+
+  allocate(c(3)[*])
+  c = [ 1, 2, 3 ]
+
+  ! standards non-conforming
+  !ERROR: 'from' argument to 'move_alloc' may not be a coindexed object
+  call move_alloc(c[1], d)
+
+  !ERROR: 'to' argument to 'move_alloc' may not be a coindexed object
+  call move_alloc(c, d[1])
+
+  !ERROR: 'stat' argument to 'move_alloc' may not be a coindexed object
+  call move_alloc(c, d, coindexed_status[1])
+
+  !ERROR: 'errmsg' argument to 'move_alloc' may not be a coindexed object
+  call move_alloc(c, d, status, coindexed_message[1])
+
+end program main