lib/Semantics/check-data.cpp

//===-- lib/Semantics/check-data.cpp --------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// DATA statement semantic analysis.
// - Applies static semantic checks to the variables in each data-stmt-set with
//   class DataVarChecker;
// - Invokes conversion of DATA statement values to static initializers

#include "check-data.h"
#include "data-to-inits.h"
#include "flang/Evaluate/traverse.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Parser/tools.h"
#include "flang/Semantics/tools.h"
#include <algorithm>
#include <vector>

namespace Fortran::semantics {

// Ensures that references to an implied DO loop control variable are
// represented as such in the "body" of the implied DO loop.
void DataChecker::Enter(const parser::DataImpliedDo &x) {
  auto name{std::get<parser::DataImpliedDo::Bounds>(x.t).name.thing.thing};
  int kind{evaluate::ResultType<evaluate::ImpliedDoIndex>::kind};
  if (const auto dynamicType{evaluate::DynamicType::From(*name.symbol)}) {
    if (dynamicType->category() == TypeCategory::Integer) {
      kind = dynamicType->kind();
    }
  }
  exprAnalyzer_.AddImpliedDo(name.source, kind);
}

void DataChecker::Leave(const parser::DataImpliedDo &x) {
  auto name{std::get<parser::DataImpliedDo::Bounds>(x.t).name.thing.thing};
  exprAnalyzer_.RemoveImpliedDo(name.source);
}

// DataVarChecker applies static checks once to each variable that appears
// in a data-stmt-set.  These checks are independent of the values that
// correspond to the variables.
class DataVarChecker : public evaluate::AllTraverse<DataVarChecker, true> {
public:
  using Base = evaluate::AllTraverse<DataVarChecker, true>;
  DataVarChecker(SemanticsContext &c, parser::CharBlock src)
      : Base{*this}, context_{c}, source_{src} {}
  using Base::operator();
  bool HasComponentWithoutSubscripts() const {
    return hasComponent_ && !hasSubscript_;
  }
  bool operator()(const Symbol &symbol) { // C876
    // 8.6.7p(2) - precludes non-pointers of derived types with
    // default component values
    const Scope &scope{context_.FindScope(source_)};
    bool isFirstSymbol{isFirstSymbol_};
    isFirstSymbol_ = false;
    if (const char *whyNot{IsAutomatic(symbol) ? "Automatic variable"
                : IsDummy(symbol)              ? "Dummy argument"
                : IsFunctionResult(symbol)     ? "Function result"
                : IsAllocatable(symbol)        ? "Allocatable"
                : IsInitialized(symbol, true)  ? "Default-initialized"
                : IsInBlankCommon(symbol)      ? "Blank COMMON object"
                : IsProcedure(symbol) && !IsPointer(symbol) ? "Procedure"
                // remaining checks don't apply to components
                : !isFirstSymbol                   ? nullptr
                : IsHostAssociated(symbol, scope)  ? "Host-associated object"
                : IsUseAssociated(symbol, scope)   ? "USE-associated object"
                : symbol.has<AssocEntityDetails>() ? "Construct association"
                                                   : nullptr}) {
      context_.Say(source_,
          "%s '%s' must not be initialized in a DATA statement"_err_en_US,
          whyNot, symbol.name());
      return false;
    } else if (IsProcedurePointer(symbol)) {
      context_.Say(source_,
          "Procedure pointer '%s' in a DATA statement is not standard"_en_US,
          symbol.name());
    }
    return true;
  }
  bool operator()(const evaluate::Component &component) {
    hasComponent_ = true;
    const Symbol &lastSymbol{component.GetLastSymbol()};
    if (isPointerAllowed_) {
      if (IsPointer(lastSymbol) && hasSubscript_) { // C877
        context_.Say(source_,
            "Rightmost data object pointer '%s' must not be subscripted"_err_en_US,
            lastSymbol.name().ToString());
        return false;
      }
      RestrictPointer();
    } else {
      if (IsPointer(lastSymbol)) { // C877
        context_.Say(source_,
            "Data object must not contain pointer '%s' as a non-rightmost part"_err_en_US,
            lastSymbol.name().ToString());
        return false;
      }
    }
    return (*this)(component.base()) && (*this)(lastSymbol);
  }
  bool operator()(const evaluate::ArrayRef &arrayRef) {
    hasSubscript_ = true;
    return (*this)(arrayRef.base()) && (*this)(arrayRef.subscript());
  }
  bool operator()(const evaluate::Substring &substring) {
    hasSubscript_ = true;
    return (*this)(substring.parent()) && (*this)(substring.lower()) &&
        (*this)(substring.upper());
  }
  bool operator()(const evaluate::CoarrayRef &) { // C874
    context_.Say(
        source_, "Data object must not be a coindexed variable"_err_en_US);
    return false;
  }
  bool operator()(const evaluate::Subscript &subs) {
    DataVarChecker subscriptChecker{context_, source_};
    subscriptChecker.RestrictPointer();
    return std::visit(
               common::visitors{
                   [&](const evaluate::IndirectSubscriptIntegerExpr &expr) {
                     return CheckSubscriptExpr(expr);
                   },
                   [&](const evaluate::Triplet &triplet) {
                     return CheckSubscriptExpr(triplet.lower()) &&
                         CheckSubscriptExpr(triplet.upper()) &&
                         CheckSubscriptExpr(triplet.stride());
                   },
               },
               subs.u) &&
        subscriptChecker(subs.u);
  }
  template <typename T>
  bool operator()(const evaluate::FunctionRef<T> &) const { // C875
    context_.Say(source_,
        "Data object variable must not be a function reference"_err_en_US);
    return false;
  }
  void RestrictPointer() { isPointerAllowed_ = false; }

private:
  bool CheckSubscriptExpr(
      const std::optional<evaluate::IndirectSubscriptIntegerExpr> &x) const {
    return !x || CheckSubscriptExpr(*x);
  }
  bool CheckSubscriptExpr(
      const evaluate::IndirectSubscriptIntegerExpr &expr) const {
    return CheckSubscriptExpr(expr.value());
  }
  bool CheckSubscriptExpr(
      const evaluate::Expr<evaluate::SubscriptInteger> &expr) const {
    if (!evaluate::IsConstantExpr(expr)) { // C875,C881
      context_.Say(
          source_, "Data object must have constant subscripts"_err_en_US);
      return false;
    } else {
      return true;
    }
  }

  SemanticsContext &context_;
  parser::CharBlock source_;
  bool hasComponent_{false};
  bool hasSubscript_{false};
  bool isPointerAllowed_{true};
  bool isFirstSymbol_{true};
};

void DataChecker::Leave(const parser::DataIDoObject &object) {
  if (const auto *designator{
          std::get_if<parser::Scalar<common::Indirection<parser::Designator>>>(
              &object.u)}) {
    if (MaybeExpr expr{exprAnalyzer_.Analyze(*designator)}) {
      auto source{designator->thing.value().source};
      if (evaluate::IsConstantExpr(*expr)) { // C878,C879
        exprAnalyzer_.context().Say(
            source, "Data implied do object must be a variable"_err_en_US);
      } else {
        DataVarChecker checker{exprAnalyzer_.context(), source};
        if (checker(*expr)) {
          if (checker.HasComponentWithoutSubscripts()) { // C880
            exprAnalyzer_.context().Say(source,
                "Data implied do structure component must be subscripted"_err_en_US);
          } else {
            return;
          }
        }
      }
    }
    currentSetHasFatalErrors_ = true;
  }
}

void DataChecker::Leave(const parser::DataStmtObject &dataObject) {
  std::visit(common::visitors{
                 [](const parser::DataImpliedDo &) { // has own Enter()/Leave()
                 },
                 [&](const auto &var) {
                   auto expr{exprAnalyzer_.Analyze(var)};
                   if (!expr ||
                       !DataVarChecker{exprAnalyzer_.context(),
                           parser::FindSourceLocation(dataObject)}(*expr)) {
                     currentSetHasFatalErrors_ = true;
                   }
                 },
             },
      dataObject.u);
}

void DataChecker::Leave(const parser::DataStmtSet &set) {
  if (!currentSetHasFatalErrors_) {
    AccumulateDataInitializations(inits_, exprAnalyzer_, set);
  }
  currentSetHasFatalErrors_ = false;
}

void DataChecker::CompileDataInitializationsIntoInitializers() {
  ConvertToInitializers(inits_, exprAnalyzer_);
}

} // namespace Fortran::semantics