[flang][hlfir] fix regression in inline elementals

InlineElementals created a regression when inlining elemental
expressions where the type of the result of the hlfir.apply does not
match the hlfir.yield.

This patch ensures the pass doesn't match in these cases, fixing the
regression.

It isn't clear to me what the /right/ solution is:
 - Is it actually valid for the hlfir.apply to have a different type
   (even just different array bounds?). Should this be enforced in the
   verifier?
 - Inserting a convert if these types don't match doesn't work because
   fir.convert doesn't know how to convert a hlfir.expr. Should this be
   added?

Test case is from @vzakhari

Differential Revision: https://reviews.llvm.org/D151202

flang/lib/Optimizer/HLFIR/Transforms/InlineElementals.cpp

@@ -51,6 +51,15 @@ getTwoUses(hlfir::ElementalOp elemental) {
 
   if (!apply || !destroy)
     return std::nullopt;
+
+  // we can't inline if the return type of the yield doesn't match the return
+  // type of the apply
+  auto yield = mlir::dyn_cast_or_null<hlfir::YieldElementOp>(
+      elemental.getRegion().back().back());
+  assert(yield && "hlfir.elemental should always end with a yield");
+  if (apply.getResult().getType() != yield.getElementValue().getType())
+    return std::nullopt;
+
   return std::pair{apply, destroy};
 }
 

flang/test/HLFIR/inline-elemental.f90

@@ -0,0 +1,15 @@
+! RUN: %flang_fc1 -emit-obj -flang-experimental-hlfir -o /dev/null %s
+
+! Regression test: ensure we can compile this without crashing
+! this results in a hlfir.elemental with mismatched types in the hlfir.apply
+! and hlfir.yield
+subroutine test
+  interface
+    function func(i,j,k)
+      character(5),allocatable :: func(:,:,:)
+    end function func
+  end interface
+  character(13),allocatable :: a(:,:,:)
+  print *, (func(2,5,3)//reshape([(char(ichar('a')+n),n=1,2*5*3)], &
+    & [2,5,3]))
+end subroutine test