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//===-- lib/Semantics/assignment.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
//
//===----------------------------------------------------------------------===//
#include "assignment.h"
#include "definable.h"
#include "pointer-assignment.h"
#include "flang/Common/idioms.h"
#include "flang/Common/restorer.h"
#include "flang/Evaluate/characteristics.h"
#include "flang/Evaluate/expression.h"
#include "flang/Evaluate/fold.h"
#include "flang/Evaluate/tools.h"
#include "flang/Parser/message.h"
#include "flang/Parser/parse-tree-visitor.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Semantics/expression.h"
#include "flang/Semantics/symbol.h"
#include "flang/Semantics/tools.h"
#include <optional>
#include <set>
#include <string>
#include <type_traits>
using namespace Fortran::parser::literals;
namespace Fortran::semantics {
class AssignmentContext {
public:
explicit AssignmentContext(SemanticsContext &context) : context_{context} {}
AssignmentContext(AssignmentContext &&) = default;
AssignmentContext(const AssignmentContext &) = delete;
bool operator==(const AssignmentContext &x) const { return this == &x; }
template <typename A> void PushWhereContext(const A &);
void PopWhereContext();
void Analyze(const parser::AssignmentStmt &);
void Analyze(const parser::PointerAssignmentStmt &);
void Analyze(const parser::ConcurrentControl &);
private:
bool CheckForPureContext(const SomeExpr &rhs, parser::CharBlock rhsSource);
void CheckShape(parser::CharBlock, const SomeExpr *);
template <typename... A>
parser::Message *Say(parser::CharBlock at, A &&...args) {
return &context_.Say(at, std::forward<A>(args)...);
}
evaluate::FoldingContext &foldingContext() {
return context_.foldingContext();
}
SemanticsContext &context_;
int whereDepth_{0}; // number of WHEREs currently nested in
// shape of masks in LHS of assignments in current WHERE:
std::vector<std::optional<std::int64_t>> whereExtents_;
};
void AssignmentContext::Analyze(const parser::AssignmentStmt &stmt) {
if (const evaluate::Assignment * assignment{GetAssignment(stmt)}) {
const SomeExpr &lhs{assignment->lhs};
const SomeExpr &rhs{assignment->rhs};
auto lhsLoc{std::get<parser::Variable>(stmt.t).GetSource()};
const Scope &scope{context_.FindScope(lhsLoc)};
if (auto whyNot{WhyNotDefinable(lhsLoc, scope,
DefinabilityFlags{DefinabilityFlag::VectorSubscriptIsOk}, lhs)}) {
if (auto *msg{Say(lhsLoc,
"Left-hand side of assignment is not definable"_err_en_US)}) {
msg->Attach(std::move(*whyNot));
}
}
auto rhsLoc{std::get<parser::Expr>(stmt.t).source};
if (std::holds_alternative<evaluate::ProcedureRef>(assignment->u)) {
// it's a defined ASSIGNMENT(=)
} else {
CheckForPureContext(rhs, rhsLoc);
}
if (whereDepth_ > 0) {
CheckShape(lhsLoc, &lhs);
}
}
}
void AssignmentContext::Analyze(const parser::PointerAssignmentStmt &stmt) {
CHECK(whereDepth_ == 0);
if (const evaluate::Assignment * assignment{GetAssignment(stmt)}) {
parser::CharBlock at{context_.location().value()};
auto restorer{foldingContext().messages().SetLocation(at)};
CheckPointerAssignment(context_, *assignment, context_.FindScope(at));
}
}
static std::optional<std::string> GetPointerComponentDesignatorName(
const SomeExpr &expr) {
if (const auto *derived{
evaluate::GetDerivedTypeSpec(evaluate::DynamicType::From(expr))}) {
PotentialAndPointerComponentIterator potentials{*derived};
if (auto pointer{
std::find_if(potentials.begin(), potentials.end(), IsPointer)}) {
return pointer.BuildResultDesignatorName();
}
}
return std::nullopt;
}
// Checks C1594(5,6); false if check fails
bool CheckCopyabilityInPureScope(parser::ContextualMessages &messages,
const SomeExpr &expr, const Scope &scope) {
if (const Symbol * base{GetFirstSymbol(expr)}) {
if (const char *why{
WhyBaseObjectIsSuspicious(base->GetUltimate(), scope)}) {
if (auto pointer{GetPointerComponentDesignatorName(expr)}) {
evaluate::SayWithDeclaration(messages, *base,
"A pure subprogram may not copy the value of '%s' because it is %s"
" and has the POINTER potential subobject component '%s'"_err_en_US,
base->name(), why, *pointer);
return false;
}
}
}
return true;
}
bool AssignmentContext::CheckForPureContext(
const SomeExpr &rhs, parser::CharBlock rhsSource) {
const Scope &scope{context_.FindScope(rhsSource)};
if (FindPureProcedureContaining(scope)) {
parser::ContextualMessages messages{
context_.location().value(), &context_.messages()};
return CheckCopyabilityInPureScope(messages, rhs, scope);
} else {
return true;
}
}
// 10.2.3.1(2) The masks and LHS of assignments must be arrays of the same shape
void AssignmentContext::CheckShape(parser::CharBlock at, const SomeExpr *expr) {
if (auto shape{evaluate::GetShape(foldingContext(), expr)}) {
std::size_t size{shape->size()};
if (size == 0) {
Say(at, "The mask or variable must not be scalar"_err_en_US);
}
if (whereDepth_ == 0) {
whereExtents_.resize(size);
} else if (whereExtents_.size() != size) {
Say(at,
"Must have rank %zd to match prior mask or assignment of"
" WHERE construct"_err_en_US,
whereExtents_.size());
return;
}
for (std::size_t i{0}; i < size; ++i) {
if (std::optional<std::int64_t> extent{evaluate::ToInt64((*shape)[i])}) {
if (!whereExtents_[i]) {
whereExtents_[i] = *extent;
} else if (*whereExtents_[i] != *extent) {
Say(at,
"Dimension %d must have extent %jd to match prior mask or"
" assignment of WHERE construct"_err_en_US,
i + 1, *whereExtents_[i]);
}
}
}
}
}
template <typename A> void AssignmentContext::PushWhereContext(const A &x) {
const auto &expr{std::get<parser::LogicalExpr>(x.t)};
CheckShape(expr.thing.value().source, GetExpr(context_, expr));
++whereDepth_;
}
void AssignmentContext::PopWhereContext() {
--whereDepth_;
if (whereDepth_ == 0) {
whereExtents_.clear();
}
}
AssignmentChecker::~AssignmentChecker() {}
AssignmentChecker::AssignmentChecker(SemanticsContext &context)
: context_{new AssignmentContext{context}} {}
void AssignmentChecker::Enter(const parser::AssignmentStmt &x) {
context_.value().Analyze(x);
}
void AssignmentChecker::Enter(const parser::PointerAssignmentStmt &x) {
context_.value().Analyze(x);
}
void AssignmentChecker::Enter(const parser::WhereStmt &x) {
context_.value().PushWhereContext(x);
}
void AssignmentChecker::Leave(const parser::WhereStmt &) {
context_.value().PopWhereContext();
}
void AssignmentChecker::Enter(const parser::WhereConstructStmt &x) {
context_.value().PushWhereContext(x);
}
void AssignmentChecker::Leave(const parser::EndWhereStmt &) {
context_.value().PopWhereContext();
}
void AssignmentChecker::Enter(const parser::MaskedElsewhereStmt &x) {
context_.value().PushWhereContext(x);
}
void AssignmentChecker::Leave(const parser::MaskedElsewhereStmt &) {
context_.value().PopWhereContext();
}
} // namespace Fortran::semantics
template class Fortran::common::Indirection<
Fortran::semantics::AssignmentContext>;
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