[flang][hlfir] Cast actual cst len character to stmt func dummy type (#68598)

When calling a statement function with a character actual argument with
a constant length mismatching the dummy length, HLFIR lowering created
an hlfir.declare with the actual argument length for the dummy, causing
bugs when lowering the statement function expression.

Ensure character dummies are always cast to the dummy type when lowering
dummy declarations.

Author: jeanPerier

flang/lib/Lower/ConvertVariable.cpp

@@ -1947,13 +1947,15 @@ void Fortran::lower::mapSymbolAttributes(
   if (ba.isChar()) {
     if (arg) {
       assert(!preAlloc && "dummy cannot be pre-allocated");
-      if (arg.getType().isa<fir::BoxCharType>()) {
+      if (arg.getType().isa<fir::BoxCharType>())
         std::tie(addr, len) = charHelp.createUnboxChar(arg);
-        // Ensure proper type is given to array/scalar that transited via
-        // fir.boxchar arg.
-        mlir::Type castTy = builder.getRefType(converter.genType(var));
-        addr = builder.createConvert(loc, castTy, addr);
-      }
+      else if (!addr)
+        addr = arg;
+      // Ensure proper type is given to array/scalar that was transmitted as a
+      // fir.boxchar arg or is a statement function actual argument with
+      // a different length than the dummy.
+      mlir::Type castTy = builder.getRefType(converter.genType(var));
+      addr = builder.createConvert(loc, castTy, addr);
     }
     if (std::optional<int64_t> cstLen = ba.getCharLenConst()) {
       // Static length

flang/test/Lower/HLFIR/statement-functions.f90

@@ -33,3 +33,17 @@ subroutine char_test(c, n)
 ! CHECK:  %[[VAL_18:.*]]:2 = hlfir.declare %[[VAL_13]]#0 typeparams %[[VAL_17]] {uniq_name = "_QFchar_testFstmt_funcEchar_stmt_func_dummy_arg"} : (!fir.ref<!fir.char<1,?>>, i32) -> (!fir.boxchar<1>, !fir.ref<!fir.char<1,?>>)
 ! CHECK:  %[[VAL_19:.*]] = arith.constant 10 : i64
 ! CHECK:  %[[VAL_20:.*]] = hlfir.set_length %[[VAL_18]]#0 len %[[VAL_19]] : (!fir.boxchar<1>, i64) -> !hlfir.expr<!fir.char<1,10>>
+
+subroutine char_test2(c)
+  character(10) :: c
+  character(5) :: c_stmt_func
+  character(*), parameter :: padding = "padding"
+  character(len(c_stmt_func)+len(padding)) :: stmt_func
+  stmt_func(c_stmt_func) = c_stmt_func // padding
+  call test(stmt_func(c))
+end subroutine
+! CHECK-LABEL:  func.func @_QPchar_test2(
+! CHECK:    %[[C:.*]]:2 = hlfir.declare %1 typeparams %c10 {uniq_name = "_QFchar_test2Ec"} : (!fir.ref<!fir.char<1,10>>, index) -> (!fir.ref<!fir.char<1,10>>, !fir.ref<!fir.char<1,10>>)
+! CHECK:    %[[CAST:.*]] = fir.convert %[[C]]#0 : (!fir.ref<!fir.char<1,10>>) -> !fir.ref<!fir.char<1,5>>
+! CHECK:    %[[C_STMT_FUNC:.*]]:2 = hlfir.declare %[[CAST]] typeparams %c5{{.*}} {uniq_name = "_QFchar_test2Fstmt_funcEc_stmt_func"} : (!fir.ref<!fir.char<1,5>>, index) -> (!fir.ref<!fir.char<1,5>>, !fir.ref<!fir.char<1,5>>)
+! CHECK:    hlfir.concat %[[C_STMT_FUNC]]#0, %{{.*}} len %{{.*}} : (!fir.ref<!fir.char<1,5>>, !fir.ref<!fir.char<1,7>>, index) -> !hlfir.expr<!fir.char<1,12>>