verilog/analysis/checkers/forbid_negative_array_dim.cc

// Copyright 2017-2023 The Verible Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "verilog/analysis/checkers/forbid_negative_array_dim.h"

#include <set>

#include "absl/strings/string_view.h"
#include "common/analysis/lint_rule_status.h"
#include "common/analysis/matcher/bound_symbol_manager.h"
#include "common/analysis/matcher/matcher.h"
#include "common/text/symbol.h"
#include "common/text/syntax_tree_context.h"
#include "common/text/token_info.h"
#include "common/text/tree_utils.h"
#include "verilog/CST/expression.h"
#include "verilog/CST/verilog_matchers.h"
#include "verilog/CST/verilog_nonterminals.h"
#include "verilog/analysis/descriptions.h"
#include "verilog/analysis/lint_rule_registry.h"
#include "verilog/parser/verilog_token_enum.h"

namespace verilog {
namespace analysis {

using verible::matcher::Matcher;

// Register the lint rule
VERILOG_REGISTER_LINT_RULE(ForbidNegativeArrayDim);

static constexpr absl::string_view kMessage =
    "Avoid using negative constant literals for array dimensions.";

const LintRuleDescriptor &ForbidNegativeArrayDim::GetDescriptor() {
  static const LintRuleDescriptor d{
      .name = "forbid-negative-array-dim",
      .topic = "forbid-negative-array-dim",
      .desc = "Check for negative constant literals inside array dimensions.",
  };
  return d;
}

// Matches the begin node.
static const Matcher &UnaryPrefixExprMatcher() {
  static const Matcher matcher(NodekUnaryPrefixExpression());
  return matcher;
}

void ForbidNegativeArrayDim::HandleSymbol(
    const verible::Symbol &symbol, const verible::SyntaxTreeContext &context) {
  // This only works for simple unary expressions. They can't be nested inside
  // other expressions. This avoids false positives of the form:
  // logic l [10+(-5):0], logic l[-(-5):0]
  if (!context.IsInsideFirst(
          {NodeEnum::kPackedDimensions, NodeEnum::kUnpackedDimensions},
          {NodeEnum::kBinaryExpression, NodeEnum::kUnaryPrefixExpression})) {
    return;
  }

  verible::matcher::BoundSymbolManager manager;
  if (!UnaryPrefixExprMatcher().Matches(symbol, &manager)) return;

  // As we've previously ensured that this symbol is a kUnaryPrefixExpression
  // both its operator and operand are defined
  const verible::TokenInfo *u_operator =
      verilog::GetUnaryPrefixOperator(symbol);
  const verible::Symbol *operand = verilog::GetUnaryPrefixOperand(symbol);

  int value = 0;
  const bool is_constant = verilog::ConstantIntegerValue(*operand, &value);
  if (is_constant && value > 0 && u_operator->text() == "-") {
    const verible::TokenInfo token(TK_OTHER,
                                   verible::StringSpanOfSymbol(symbol));
    violations_.insert(verible::LintViolation(token, kMessage, context));
  }
}

verible::LintRuleStatus ForbidNegativeArrayDim::Report() const {
  return verible::LintRuleStatus(violations_, GetDescriptor());
}

}  // namespace analysis
}  // namespace verilog