[flang-commits] [flang] Get the BoxType from the RHS instead of LHS for polymorphic pointer assignment inside FORALL. (PR #164279)

[Daniel Chen via flang-commits]

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@@ -4730,13 +4730,14 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     if (Fortran::evaluate::UnwrapExpr<Fortran::evaluate::NullPointer>(
             assign.rhs))
       return fir::factory::createUnallocatedBox(*builder, loc, lhsBoxType, {});
-    hlfir::Entity rhs = Fortran::lower::convertExprToHLFIR(
-        loc, *this, assign.rhs, localSymbols, rhsContext);
+    hlfir::Entity rhs{fir::getBase(genExprBox(loc, assign.rhs, rhsContext))};
+    auto rhsBoxType =
+        llvm::cast<fir::BaseBoxType>(fir::unwrapRefType(rhs.getType()));
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DanielCChen wrote:

@jeanPerier 
Thanks for the quick review and the suggesion!
I tried your suggestion, but got core dump as
```
flang: /scratch/cdchen/FLANG/llvm-project/llvm/include/llvm/Support/Casting.h:560: decltype(auto) llvm::cast(const From &) [To = fir::BaseBoxType, From = mlir::Type]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
```

The expected `rhsBoxType` should be `!fir.box<!fir.char<1>>`, which is what the the current patch returns.
However, with `convertExprToHLFIR`, I got `!fir.ref<!fir.char<1>>`. 

The code `fir::getBase(genExprBox(loc, assign.rhs, rhsContext))` is also used by the exact same pointer assignment inside a DO loop (in comparison to FORALL).


https://github.com/llvm/llvm-project/pull/164279