[flang] Refine "same type" testing for intrinsic arguments

Some errors aren't being caught, such as the case in the linked bug
where the PAD= argument to RESHAPE() didn't have the same declared
type as the ARRAY=; this led to a crash in lowering.  Refine the
"same type" testing logic for intrinsic procedures, and add a
better test.

Fixes #124976.

Author: klausler

flang/lib/Evaluate/intrinsics.cpp

@@ -2032,16 +2032,21 @@ std::optional<SpecificCall> IntrinsicInterface::Match(
       dimArg = j;
       argOk = true;
       break;
-    case KindCode::same:
+    case KindCode::same: {
       if (!sameArg) {
         sameArg = arg;
-        argOk = true;
+      }
+      auto sameType{sameArg->GetType().value()};
+      if (name == "move_alloc"s) {
+        // second argument can be more general
+        argOk = type->IsTkLenCompatibleWith(sameType);
+      } else if (name == "merge"s) {
+        argOk = type->IsTkLenCompatibleWith(sameType) &&
+            sameType.IsTkLenCompatibleWith(*type);
       } else {
-        auto sameType{sameArg->GetType().value()};
-        argOk = sameType.IsTkLenCompatibleWith(*type) ||
-            (name == "move_alloc"s && type->IsTkLenCompatibleWith(sameType));
+        argOk = sameType.IsTkLenCompatibleWith(*type);
       }
-      break;
+    } break;
     case KindCode::sameKind:
       if (!sameArg) {
         sameArg = arg;

flang/test/Semantics/bug124976.f90

@@ -0,0 +1,33 @@
+!RUN: %python %S/test_errors.py %s %flang_fc1
+program main
+  type base
+    integer :: x = 1
+  end type
+  type, extends(base) :: child
+    integer :: y = 2
+  end type
+  class(child), allocatable :: c1(:), c2(:,:)
+  class(base), allocatable :: b1(:), b2(:,:)
+  logical var(1)
+  common /blk/ var
+  allocate(c1(2), c2(2,2), b1(2), b2(2,2))
+  !ERROR: Actual argument for 'pad=' has bad type or kind 'CLASS(base)'
+  c2 = reshape(c1, shape(c2), pad=b1)
+  b2 = reshape(b1, shape(b2), pad=c1) ! ok
+  !ERROR: Actual argument for 'to=' has bad type or kind 'CLASS(child)'
+  call move_alloc(b1, c1)
+  call move_alloc(c1, b1) ! ok
+  !ERROR: Actual argument for 'boundary=' has bad type or kind 'CLASS(base)'
+  c1 = eoshift(c1, 1, b1(1))
+  c1 = eoshift(c1, 1, c2(1,1)) ! ok
+  b1 = eoshift(b1, 1, c1(1)) ! ok
+  !ERROR: Actual argument for 'fsource=' has bad type or kind 'CLASS(child)'
+  b1 = merge(b1, c1, var(1))
+  !ERROR: Actual argument for 'fsource=' has bad type or kind 'CLASS(base)'
+  b1 = merge(c1, b1, var(1))
+  b1 = merge(b1, b1, var(1)) ! ok
+  !ERROR: Actual argument for 'vector=' has bad type or kind 'CLASS(base)'
+  c1 = pack(c1, var, b1)
+  c1 = pack(c1, var, c1) ! ok
+  b1 = pack(b1, var, c1) ! ok
+end