/*
 * Copyright 2016 WebAssembly Community Group participants
 *
 * 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 "src/validator.h"

#include <cassert>
#include <cinttypes>
#include <cstdarg>
#include <cstdio>

#include "config.h"

#include "src/binary-reader.h"
#include "src/cast.h"
#include "src/expr-visitor.h"
#include "src/ir.h"
#include "src/type-checker.h"

namespace wabt {

namespace {

class Validator : public ExprVisitor::Delegate {
 public:
  WABT_DISALLOW_COPY_AND_ASSIGN(Validator);
  Validator(Errors*, const Script*, const ValidateOptions& options);

  Result CheckModule(const Module* module);
  Result CheckScript(const Script* script);
  Result CheckAllFuncSignatures(const Module* module);

  // Implements ExprVisitor::Delegate.
  Result OnBinaryExpr(BinaryExpr*) override;
  Result BeginBlockExpr(BlockExpr*) override;
  Result EndBlockExpr(BlockExpr*) override;
  Result OnBrExpr(BrExpr*) override;
  Result OnBrIfExpr(BrIfExpr*) override;
  Result OnBrOnExnExpr(BrOnExnExpr*) override;
  Result OnBrTableExpr(BrTableExpr*) override;
  Result OnCallExpr(CallExpr*) override;
  Result OnCallIndirectExpr(CallIndirectExpr*) override;
  Result OnCompareExpr(CompareExpr*) override;
  Result OnConstExpr(ConstExpr*) override;
  Result OnConvertExpr(ConvertExpr*) override;
  Result OnDropExpr(DropExpr*) override;
  Result OnGlobalGetExpr(GlobalGetExpr*) override;
  Result OnGlobalSetExpr(GlobalSetExpr*) override;
  Result BeginIfExpr(IfExpr*) override;
  Result AfterIfTrueExpr(IfExpr*) override;
  Result EndIfExpr(IfExpr*) override;
  Result OnLoadExpr(LoadExpr*) override;
  Result OnLocalGetExpr(LocalGetExpr*) override;
  Result OnLocalSetExpr(LocalSetExpr*) override;
  Result OnLocalTeeExpr(LocalTeeExpr*) override;
  Result BeginLoopExpr(LoopExpr*) override;
  Result EndLoopExpr(LoopExpr*) override;
  Result OnMemoryCopyExpr(MemoryCopyExpr*) override;
  Result OnDataDropExpr(DataDropExpr*) override;
  Result OnMemoryFillExpr(MemoryFillExpr*) override;
  Result OnMemoryGrowExpr(MemoryGrowExpr*) override;
  Result OnMemoryInitExpr(MemoryInitExpr*) override;
  Result OnMemorySizeExpr(MemorySizeExpr*) override;
  Result OnTableCopyExpr(TableCopyExpr*) override;
  Result OnElemDropExpr(ElemDropExpr*) override;
  Result OnTableInitExpr(TableInitExpr*) override;
  Result OnTableGetExpr(TableGetExpr*) override;
  Result OnTableSetExpr(TableSetExpr*) override;
  Result OnTableGrowExpr(TableGrowExpr*) override;
  Result OnTableSizeExpr(TableSizeExpr*) override;
  Result OnRefNullExpr(RefNullExpr*) override;
  Result OnRefIsNullExpr(RefIsNullExpr*) override;
  Result OnNopExpr(NopExpr*) override;
  Result OnReturnExpr(ReturnExpr*) override;
  Result OnReturnCallExpr(ReturnCallExpr*) override;
  Result OnReturnCallIndirectExpr(ReturnCallIndirectExpr*) override;
  Result OnSelectExpr(SelectExpr*) override;
  Result OnStoreExpr(StoreExpr*) override;
  Result OnUnaryExpr(UnaryExpr*) override;
  Result OnUnreachableExpr(UnreachableExpr*) override;
  Result BeginTryExpr(TryExpr*) override;
  Result OnCatchExpr(TryExpr*) override;
  Result EndTryExpr(TryExpr*) override;
  Result OnThrowExpr(ThrowExpr*) override;
  Result OnRethrowExpr(RethrowExpr*) override;
  Result OnAtomicWaitExpr(AtomicWaitExpr*) override;
  Result OnAtomicNotifyExpr(AtomicNotifyExpr*) override;
  Result OnAtomicLoadExpr(AtomicLoadExpr*) override;
  Result OnAtomicStoreExpr(AtomicStoreExpr*) override;
  Result OnAtomicRmwExpr(AtomicRmwExpr*) override;
  Result OnAtomicRmwCmpxchgExpr(AtomicRmwCmpxchgExpr*) override;
  Result OnTernaryExpr(TernaryExpr*) override;
  Result OnSimdLaneOpExpr(SimdLaneOpExpr*) override;
  Result OnSimdShuffleOpExpr(SimdShuffleOpExpr*) override;

 private:
  struct ActionResult {
    enum class Kind {
      Error,
      Types,
      Type,
    } kind;

    union {
      const TypeVector* types;
      Type type;
    };
  };

  void WABT_PRINTF_FORMAT(3, 4)
      PrintError(const Location* loc, const char* fmt, ...);
  void OnTypecheckerError(const char* msg);
  Result CheckVar(Index max_index,
                  const Var* var,
                  const char* desc,
                  Index* out_index);
  Result CheckFuncVar(const Var* var, const Func** out_func);
  Result CheckGlobalVar(const Var* var,
                        const Global** out_global,
                        Index* out_global_index);
  Type GetGlobalVarTypeOrAny(const Var* var);
  Result CheckFuncTypeVar(const Var* var, const FuncType** out_func_type);
  Result CheckTableVar(const Var* var, const Table** out_table);
  Result CheckMemoryVar(const Var* var, const Memory** out_memory);
  Result CheckDataSegmentVar(const Var* var);
  Result CheckElemSegmentVar(const Var* var);
  Result CheckLocalVar(const Var* var, Type* out_type);
  Type GetLocalVarTypeOrAny(const Var* var);
  void CheckAlign(const Location* loc,
                  Address alignment,
                  Address natural_alignment);
  void CheckAtomicAlign(const Location* loc,
                        Address alignment,
                        Address natural_alignment);
  void CheckType(const Location* loc,
                 Type actual,
                 Type expected,
                 const char* desc);
  void CheckTypeIndex(const Location* loc,
                      Type actual,
                      Type expected,
                      const char* desc,
                      Index index,
                      const char* index_kind);
  void CheckTypes(const Location* loc,
                  const TypeVector& actual,
                  const TypeVector& expected,
                  const char* desc,
                  const char* index_kind);
  void CheckConstTypes(const Location* loc,
                       const TypeVector& actual,
                       const ConstVector& expected,
                       const char* desc);
  void CheckConstType(const Location* loc,
                      Type actual,
                      const ConstVector& expected,
                      const char* desc);
  void CheckAssertReturnNanType(const Location* loc,
                                Type actual,
                                const char* desc);
  void CheckExprList(const Location* loc, const ExprList& exprs);
  bool CheckHasMemory(const Location* loc, Opcode opcode);
  bool CheckHasTable(const Location* loc, Opcode opcode, Index index = 0);
  void CheckHasSharedMemory(const Location* loc, Opcode opcode);
  void CheckBlockDeclaration(const Location* loc,
                             Opcode opcode,
                             const BlockDeclaration* decl);
  template <typename T>
  void CheckAtomicExpr(const T* expr, Result (TypeChecker::*func)(Opcode));
  void CheckFuncSignature(const Location* loc, const FuncDeclaration& decl);
  class CheckFuncSignatureExprVisitorDelegate;

  void CheckFunc(const Location* loc, const Func* func);
  void PrintConstExprError(const Location* loc, const char* desc);
  void CheckConstInitExpr(const Location* loc,
                          const ExprList& expr,
                          Type expected_type,
                          const char* desc);
  void CheckGlobal(const Location* loc, const Global* global);
  void CheckLimits(const Location* loc,
                   const Limits* limits,
                   uint64_t absolute_max,
                   const char* desc);
  void CheckTable(const Location* loc, const Table* table);
  void CheckElemSegments(const Module* module);
  void CheckMemory(const Location* loc, const Memory* memory);
  void CheckDataSegments(const Module* module);
  void CheckImport(const Location* loc, const Import* import);
  void CheckExport(const Location* loc, const Export* export_);

  void CheckDuplicateExportBindings(const Module* module);
  const TypeVector* CheckInvoke(const InvokeAction* action);
  Result CheckGet(const GetAction* action, Type* out_type);
  ActionResult CheckAction(const Action* action);
  void CheckAssertReturnNanCommand(const Action* action);
  void CheckCommand(const Command* command);

  void CheckEvent(const Location* loc, const Event* Event);
  Result CheckEventVar(const Var* var, const Event** out_event);

  const ValidateOptions& options_;
  Errors* errors_ = nullptr;
  const Script* script_ = nullptr;
  const Module* current_module_ = nullptr;
  const Func* current_func_ = nullptr;
  Index current_table_index_ = 0;
  Index current_memory_index_ = 0;
  Index current_global_index_ = 0;
  Index num_imported_globals_ = 0;
  Index current_event_index_ = 0;
  TypeChecker typechecker_;
  // Cached for access by OnTypecheckerError.
  const Location* expr_loc_ = nullptr;
  Result result_ = Result::Ok;
};

Validator::Validator(Errors* errors,
                     const Script* script,
                     const ValidateOptions& options)
    : options_(options), errors_(errors), script_(script) {
  typechecker_.set_error_callback(
      [this](const char* msg) { OnTypecheckerError(msg); });
}

void Validator::PrintError(const Location* loc, const char* format, ...) {
  result_ = Result::Error;
  WABT_SNPRINTF_ALLOCA(buffer, length, format);
  errors_->emplace_back(ErrorLevel::Error, *loc, buffer);
}

void Validator::OnTypecheckerError(const char* msg) {
  PrintError(expr_loc_, "%s", msg);
}

static bool is_power_of_two(uint32_t x) {
  return x && ((x & (x - 1)) == 0);
}

static Address get_opcode_natural_alignment(Opcode opcode) {
  Address memory_size = opcode.GetMemorySize();
  assert(memory_size != 0);
  return memory_size;
}

Result Validator::CheckVar(Index max_index,
                           const Var* var,
                           const char* desc,
                           Index* out_index) {
  if (var->index() < max_index) {
    if (out_index) {
      *out_index = var->index();
    }
    return Result::Ok;
  }
  PrintError(&var->loc, "%s variable out of range (max %" PRIindex ")", desc,
             max_index);
  return Result::Error;
}

Result Validator::CheckFuncVar(const Var* var, const Func** out_func) {
  Index index;
  CHECK_RESULT(
      CheckVar(current_module_->funcs.size(), var, "function", &index));
  if (out_func) {
    *out_func = current_module_->funcs[index];
  }
  return Result::Ok;
}

Result Validator::CheckGlobalVar(const Var* var,
                                 const Global** out_global,
                                 Index* out_global_index) {
  Index index;
  CHECK_RESULT(
      CheckVar(current_module_->globals.size(), var, "global", &index));
  if (out_global) {
    *out_global = current_module_->globals[index];
  }
  if (out_global_index) {
    *out_global_index = index;
  }
  return Result::Ok;
}

Type Validator::GetGlobalVarTypeOrAny(const Var* var) {
  const Global* global;
  if (Succeeded(CheckGlobalVar(var, &global, nullptr))) {
    return global->type;
  }
  return Type::Any;
}

Result Validator::CheckFuncTypeVar(const Var* var,
                                   const FuncType** out_func_type) {
  Index index;
  CHECK_RESULT(CheckVar(current_module_->func_types.size(), var,
                        "function type", &index));
  if (out_func_type) {
    *out_func_type = current_module_->func_types[index];
  }
  return Result::Ok;
}

Result Validator::CheckTableVar(const Var* var, const Table** out_table) {
  Index index;
  CHECK_RESULT(CheckVar(current_module_->tables.size(), var, "table", &index));
  if (out_table) {
    *out_table = current_module_->tables[index];
  }
  return Result::Ok;
}

Result Validator::CheckMemoryVar(const Var* var, const Memory** out_memory) {
  Index index;
  CHECK_RESULT(
      CheckVar(current_module_->memories.size(), var, "memory", &index));
  if (out_memory) {
    *out_memory = current_module_->memories[index];
  }
  return Result::Ok;
}

Result Validator::CheckDataSegmentVar(const Var* var) {
  Index index;
  CHECK_RESULT(CheckVar(current_module_->data_segments.size(), var,
                        "data_segment", &index));
  return Result::Ok;
}

Result Validator::CheckElemSegmentVar(const Var* var) {
  Index index;
  CHECK_RESULT(CheckVar(current_module_->elem_segments.size(), var,
                        "elem_segment", &index));
  return Result::Ok;
}

Result Validator::CheckLocalVar(const Var* var, Type* out_type) {
  const Func* func = current_func_;
  Index max_index = func->GetNumParamsAndLocals();
  Index index = func->GetLocalIndex(*var);
  if (index < max_index) {
    if (out_type) {
      Index num_params = func->GetNumParams();
      if (index < num_params) {
        *out_type = func->GetParamType(index);
      } else {
        *out_type = current_func_->local_types[index - num_params];
      }
    }
    return Result::Ok;
  }

  if (var->is_name()) {
    PrintError(&var->loc, "undefined local variable \"%s\"",
               var->name().c_str());
  } else {
    PrintError(&var->loc, "local variable out of range (max %" PRIindex ")",
               max_index);
  }
  return Result::Error;
}

Type Validator::GetLocalVarTypeOrAny(const Var* var) {
  Type type = Type::Any;
  CheckLocalVar(var, &type);
  return type;
}

void Validator::CheckAlign(const Location* loc,
                           Address alignment,
                           Address natural_alignment) {
  if (alignment != WABT_USE_NATURAL_ALIGNMENT) {
    if (!is_power_of_two(alignment)) {
      PrintError(loc, "alignment must be power-of-two");
    }
    if (alignment > natural_alignment) {
      PrintError(loc,
                 "alignment must not be larger than natural alignment (%u)",
                 natural_alignment);
    }
  }
}

void Validator::CheckAtomicAlign(const Location* loc,
                                 Address alignment,
                                 Address natural_alignment) {
  if (alignment != WABT_USE_NATURAL_ALIGNMENT) {
    if (!is_power_of_two(alignment)) {
      PrintError(loc, "alignment must be power-of-two");
    }
    if (alignment != natural_alignment) {
      PrintError(loc, "alignment must be equal to natural alignment (%u)",
                 natural_alignment);
    }
  }
}

void Validator::CheckType(const Location* loc,
                          Type actual,
                          Type expected,
                          const char* desc) {
  if (expected != actual) {
    PrintError(loc, "type mismatch at %s. got %s, expected %s", desc,
               GetTypeName(actual), GetTypeName(expected));
  }
}

void Validator::CheckTypeIndex(const Location* loc,
                               Type actual,
                               Type expected,
                               const char* desc,
                               Index index,
                               const char* index_kind) {
  if (expected != actual && expected != Type::Any && actual != Type::Any) {
    PrintError(
        loc, "type mismatch for %s %" PRIindex " of %s. got %s, expected %s",
        index_kind, index, desc, GetTypeName(actual), GetTypeName(expected));
  }
}

void Validator::CheckTypes(const Location* loc,
                           const TypeVector& actual,
                           const TypeVector& expected,
                           const char* desc,
                           const char* index_kind) {
  if (actual.size() == expected.size()) {
    for (size_t i = 0; i < actual.size(); ++i) {
      CheckTypeIndex(loc, actual[i], expected[i], desc, i, index_kind);
    }
  } else {
    PrintError(loc, "expected %" PRIzd " %ss, got %" PRIzd, expected.size(),
               index_kind, actual.size());
  }
}

void Validator::CheckConstTypes(const Location* loc,
                                const TypeVector& actual,
                                const ConstVector& expected,
                                const char* desc) {
  if (actual.size() == expected.size()) {
    for (size_t i = 0; i < actual.size(); ++i) {
      CheckTypeIndex(loc, actual[i], expected[i].type, desc, i, "result");
    }
  } else {
    PrintError(loc, "expected %" PRIzd " results, got %" PRIzd, expected.size(),
               actual.size());
  }
}

void Validator::CheckConstType(const Location* loc,
                               Type actual,
                               const ConstVector& expected,
                               const char* desc) {
  TypeVector actual_types;
  if (actual != Type::Void) {
    actual_types.push_back(actual);
  }
  CheckConstTypes(loc, actual_types, expected, desc);
}

void Validator::CheckAssertReturnNanType(const Location* loc,
                                         Type actual,
                                         const char* desc) {
  // When using assert_return_nan, the result can be either a f32 or f64 type
  // so we special case it here.
  if (actual != Type::F32 && actual != Type::F64) {
    PrintError(loc, "type mismatch at %s. got %s, expected f32 or f64", desc,
               GetTypeName(actual));
  }
}

void Validator::CheckExprList(const Location* loc, const ExprList& exprs) {
  ExprVisitor visitor(this);
  // TODO(binji): Add const-visitors.
  visitor.VisitExprList(const_cast<ExprList&>(exprs));
}

bool Validator::CheckHasMemory(const Location* loc, Opcode opcode) {
  if (current_module_->memories.size() == 0) {
    PrintError(loc, "%s requires an imported or defined memory.",
               opcode.GetName());
    return false;
  }

  return true;
}

bool Validator::CheckHasTable(const Location* loc, Opcode opcode, Index index) {
  if (current_module_->tables.size() <= index) {
    PrintError(loc, "%s requires table %d to be an imported or defined table.",
               opcode.GetName(), index);
    return false;
  }

  return true;
}

void Validator::CheckHasSharedMemory(const Location* loc, Opcode opcode) {
  if (CheckHasMemory(loc, opcode)) {
    Memory* memory = current_module_->memories[0];
    if (!memory->page_limits.is_shared) {
      PrintError(loc, "%s requires memory to be shared.", opcode.GetName());
    }
  }
}

void Validator::CheckBlockDeclaration(const Location* loc,
                                      Opcode opcode,
                                      const BlockDeclaration* decl) {
  if (decl->sig.GetNumParams() > 0 &&
      !options_.features.multi_value_enabled()) {
    PrintError(loc, "%s params not currently supported.", opcode.GetName());
  }
  if (decl->sig.GetNumResults() > 1 &&
      !options_.features.multi_value_enabled()) {
    PrintError(loc, "multiple %s results not currently supported.",
               opcode.GetName());
  }
  if (decl->has_func_type) {
    const FuncType* func_type;
    if (Succeeded(CheckFuncTypeVar(&decl->type_var, &func_type))) {
      CheckTypes(loc, decl->sig.result_types, func_type->sig.result_types,
                 opcode.GetName(), "result");
      CheckTypes(loc, decl->sig.param_types, func_type->sig.param_types,
                 opcode.GetName(), "argument");
    }
  }
}

template <typename T>
void Validator::CheckAtomicExpr(const T* expr,
                                Result (TypeChecker::*func)(Opcode)) {
  CheckHasSharedMemory(&expr->loc, expr->opcode);
  CheckAtomicAlign(&expr->loc, expr->align,
                   get_opcode_natural_alignment(expr->opcode));
  (typechecker_.*func)(expr->opcode);
}

Result Validator::OnBinaryExpr(BinaryExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnBinary(expr->opcode);
  return Result::Ok;
}

Result Validator::BeginBlockExpr(BlockExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckBlockDeclaration(&expr->loc, Opcode::Block, &expr->block.decl);
  typechecker_.OnBlock(expr->block.decl.sig.param_types,
                       expr->block.decl.sig.result_types);
  return Result::Ok;
}

Result Validator::EndBlockExpr(BlockExpr* expr) {
  expr_loc_ = &expr->block.end_loc;
  typechecker_.OnEnd();
  return Result::Ok;
}

Result Validator::OnBrExpr(BrExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnBr(expr->var.index());
  return Result::Ok;
}

Result Validator::OnBrIfExpr(BrIfExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnBrIf(expr->var.index());
  return Result::Ok;
}

Result Validator::OnBrOnExnExpr(BrOnExnExpr* expr) {
  expr_loc_ = &expr->loc;
  const Event* event;
  if (Succeeded(CheckEventVar(&expr->event_var, &event))) {
    typechecker_.OnBrOnExn(expr->label_var.index(),
                           event->decl.sig.param_types);
  }
  return Result::Ok;
}

Result Validator::OnBrTableExpr(BrTableExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.BeginBrTable();
  for (const Var& var : expr->targets) {
    typechecker_.OnBrTableTarget(var.index());
  }
  typechecker_.OnBrTableTarget(expr->default_target.index());
  typechecker_.EndBrTable();
  return Result::Ok;
}

Result Validator::OnCallExpr(CallExpr* expr) {
  expr_loc_ = &expr->loc;
  const Func* callee;
  if (Succeeded(CheckFuncVar(&expr->var, &callee))) {
    typechecker_.OnCall(callee->decl.sig.param_types,
                        callee->decl.sig.result_types);
  }
  return Result::Ok;
}

Result Validator::OnCallIndirectExpr(CallIndirectExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::CallIndirect, expr->table.index());
  CheckFuncSignature(&expr->loc, expr->decl);
  typechecker_.OnCallIndirect(expr->decl.sig.param_types,
                              expr->decl.sig.result_types);
  return Result::Ok;
}

Result Validator::OnCompareExpr(CompareExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnCompare(expr->opcode);
  return Result::Ok;
}

Result Validator::OnConstExpr(ConstExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnConst(expr->const_.type);
  return Result::Ok;
}

Result Validator::OnConvertExpr(ConvertExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnConvert(expr->opcode);
  return Result::Ok;
}

Result Validator::OnDropExpr(DropExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnDrop();
  return Result::Ok;
}

Result Validator::OnGlobalGetExpr(GlobalGetExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnGlobalGet(GetGlobalVarTypeOrAny(&expr->var));
  return Result::Ok;
}

Result Validator::OnGlobalSetExpr(GlobalSetExpr* expr) {
  expr_loc_ = &expr->loc;
  Type type = Type::Any;
  const Global* global;
  Index global_index;
  if (Succeeded(CheckGlobalVar(&expr->var, &global, &global_index))) {
    if (!global->mutable_) {
      PrintError(&expr->loc,
                 "can't global.set on immutable global at index %" PRIindex ".",
                 global_index);
    }
    type = global->type;
  }
  typechecker_.OnGlobalSet(type);
  return Result::Ok;
}

Result Validator::BeginIfExpr(IfExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckBlockDeclaration(&expr->loc, Opcode::If, &expr->true_.decl);
  typechecker_.OnIf(expr->true_.decl.sig.param_types,
                    expr->true_.decl.sig.result_types);
  return Result::Ok;
}

Result Validator::AfterIfTrueExpr(IfExpr* expr) {
  if (!expr->false_.empty()) {
    typechecker_.OnElse();
  }
  return Result::Ok;
}

Result Validator::EndIfExpr(IfExpr* expr) {
  expr_loc_ =
      expr->false_.empty() ? &expr->true_.end_loc : &expr->false_end_loc;
  typechecker_.OnEnd();
  return Result::Ok;
}

Result Validator::OnLoadExpr(LoadExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, expr->opcode);
  CheckAlign(&expr->loc, expr->align,
             get_opcode_natural_alignment(expr->opcode));
  typechecker_.OnLoad(expr->opcode);
  return Result::Ok;
}

Result Validator::OnLocalGetExpr(LocalGetExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnLocalGet(GetLocalVarTypeOrAny(&expr->var));
  return Result::Ok;
}

Result Validator::OnLocalSetExpr(LocalSetExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnLocalSet(GetLocalVarTypeOrAny(&expr->var));
  return Result::Ok;
}

Result Validator::OnLocalTeeExpr(LocalTeeExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnLocalTee(GetLocalVarTypeOrAny(&expr->var));
  return Result::Ok;
}

Result Validator::BeginLoopExpr(LoopExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckBlockDeclaration(&expr->loc, Opcode::Loop, &expr->block.decl);
  typechecker_.OnLoop(expr->block.decl.sig.param_types,
                      expr->block.decl.sig.result_types);
  return Result::Ok;
}

Result Validator::EndLoopExpr(LoopExpr* expr) {
  expr_loc_ = &expr->block.end_loc;
  typechecker_.OnEnd();
  return Result::Ok;
}

Result Validator::OnMemoryCopyExpr(MemoryCopyExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::MemoryCopy);
  typechecker_.OnMemoryCopy();
  return Result::Ok;
}

Result Validator::OnDataDropExpr(DataDropExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::DataDrop);
  CheckDataSegmentVar(&expr->var);
  typechecker_.OnDataDrop(expr->var.index());
  return Result::Ok;
}

Result Validator::OnMemoryFillExpr(MemoryFillExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::MemoryFill);
  typechecker_.OnMemoryFill();
  return Result::Ok;
}

Result Validator::OnMemoryGrowExpr(MemoryGrowExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::MemoryGrow);
  typechecker_.OnMemoryGrow();
  return Result::Ok;
}

Result Validator::OnMemoryInitExpr(MemoryInitExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::MemoryInit);
  CheckDataSegmentVar(&expr->var);
  typechecker_.OnMemoryInit(expr->var.index());
  return Result::Ok;
}

Result Validator::OnMemorySizeExpr(MemorySizeExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, Opcode::MemorySize);
  typechecker_.OnMemorySize();
  return Result::Ok;
}

Result Validator::OnTableCopyExpr(TableCopyExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableCopy);
  typechecker_.OnTableCopy();
  return Result::Ok;
}

Result Validator::OnElemDropExpr(ElemDropExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::ElemDrop);
  CheckElemSegmentVar(&expr->var);
  typechecker_.OnElemDrop(expr->var.index());
  return Result::Ok;
}

Result Validator::OnTableInitExpr(TableInitExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableInit);
  CheckElemSegmentVar(&expr->var);
  typechecker_.OnTableInit(expr->var.index());
  return Result::Ok;
}

Result Validator::OnTableGetExpr(TableGetExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableGet, expr->var.index());
  typechecker_.OnTableGet(expr->var.index());
  return Result::Ok;
}

Result Validator::OnTableSetExpr(TableSetExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableSet, expr->var.index());
  typechecker_.OnTableSet(expr->var.index());
  return Result::Ok;
}

Result Validator::OnTableGrowExpr(TableGrowExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableGrow, expr->var.index());
  typechecker_.OnTableGrow(expr->var.index());
  return Result::Ok;
}

Result Validator::OnTableSizeExpr(TableSizeExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::TableSize, expr->var.index());
  typechecker_.OnTableSize(expr->var.index());
  return Result::Ok;
}

Result Validator::OnRefNullExpr(RefNullExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnRefNullExpr();
  return Result::Ok;
}

Result Validator::OnRefIsNullExpr(RefIsNullExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnRefIsNullExpr();
  return Result::Ok;
}

Result Validator::OnNopExpr(NopExpr* expr) {
  expr_loc_ = &expr->loc;
  return Result::Ok;
}

Result Validator::OnReturnExpr(ReturnExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnReturn();
  return Result::Ok;
}

Result Validator::OnReturnCallExpr(ReturnCallExpr* expr) {
  expr_loc_ = &expr->loc;
  const Func* callee;
  if (Succeeded(CheckFuncVar(&expr->var, &callee))) {
    typechecker_.OnReturnCall(callee->decl.sig.param_types,
                        callee->decl.sig.result_types);
  }
  return Result::Ok;
}

Result Validator::OnReturnCallIndirectExpr(ReturnCallIndirectExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasTable(&expr->loc, Opcode::ReturnCallIndirect, expr->table.index());
  CheckFuncSignature(&expr->loc, expr->decl);
  typechecker_.OnReturnCallIndirect(expr->decl.sig.param_types,
                              expr->decl.sig.result_types);
  return Result::Ok;
}

Result Validator::OnSelectExpr(SelectExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnSelect();
  return Result::Ok;
}

Result Validator::OnStoreExpr(StoreExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckHasMemory(&expr->loc, expr->opcode);
  CheckAlign(&expr->loc, expr->align,
             get_opcode_natural_alignment(expr->opcode));
  typechecker_.OnStore(expr->opcode);
  return Result::Ok;
}

Result Validator::OnUnaryExpr(UnaryExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnUnary(expr->opcode);
  return Result::Ok;
}

Result Validator::OnUnreachableExpr(UnreachableExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnUnreachable();
  return Result::Ok;
}

Result Validator::BeginTryExpr(TryExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckBlockDeclaration(&expr->loc, Opcode::Try, &expr->block.decl);
  typechecker_.OnTry(expr->block.decl.sig.param_types,
                     expr->block.decl.sig.result_types);
  return Result::Ok;
}

Result Validator::OnCatchExpr(TryExpr* expr) {
  typechecker_.OnCatch();
  return Result::Ok;
}

Result Validator::EndTryExpr(TryExpr* expr) {
  expr_loc_ = &expr->block.end_loc;
  typechecker_.OnEnd();
  return Result::Ok;
}

Result Validator::OnThrowExpr(ThrowExpr* expr) {
  expr_loc_ = &expr->loc;
  const Event* event;
  if (Succeeded(CheckEventVar(&expr->var, &event))) {
    typechecker_.OnThrow(event->decl.sig.param_types);
  }
  return Result::Ok;
}

Result Validator::OnRethrowExpr(RethrowExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnRethrow();
  return Result::Ok;
}

Result Validator::OnAtomicWaitExpr(AtomicWaitExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicWait);
  return Result::Ok;
}

Result Validator::OnAtomicNotifyExpr(AtomicNotifyExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicNotify);
  return Result::Ok;
}

Result Validator::OnAtomicLoadExpr(AtomicLoadExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicLoad);
  return Result::Ok;
}

Result Validator::OnAtomicStoreExpr(AtomicStoreExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicStore);
  return Result::Ok;
}

Result Validator::OnAtomicRmwExpr(AtomicRmwExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicRmw);
  return Result::Ok;
}

Result Validator::OnAtomicRmwCmpxchgExpr(AtomicRmwCmpxchgExpr* expr) {
  expr_loc_ = &expr->loc;
  CheckAtomicExpr(expr, &TypeChecker::OnAtomicRmwCmpxchg);
  return Result::Ok;
}

Result Validator::OnTernaryExpr(TernaryExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnTernary(expr->opcode);
  return Result::Ok;
}

Result Validator::OnSimdLaneOpExpr(SimdLaneOpExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnSimdLaneOp(expr->opcode, expr->val);
  return Result::Ok;
}

Result Validator::OnSimdShuffleOpExpr(SimdShuffleOpExpr* expr) {
  expr_loc_ = &expr->loc;
  typechecker_.OnSimdShuffleOp(expr->opcode, expr->val);
  return Result::Ok;
}

void Validator::CheckFuncSignature(const Location* loc,
                                   const FuncDeclaration& decl) {
  if (decl.has_func_type) {
    const FuncType* func_type;
    if (Succeeded(CheckFuncTypeVar(&decl.type_var, &func_type))) {
      CheckTypes(loc, decl.sig.result_types, func_type->sig.result_types,
                 "function", "result");
      CheckTypes(loc, decl.sig.param_types, func_type->sig.param_types,
                 "function", "argument");
    }
  }
}

void Validator::CheckFunc(const Location* loc, const Func* func) {
  current_func_ = func;
  CheckFuncSignature(loc, func->decl);
  if (!options_.features.multi_value_enabled() && func->GetNumResults() > 1) {
    PrintError(loc, "multiple result values not currently supported.");
    // Don't run any other checks, the won't test the result_type properly.
    return;
  }

  expr_loc_ = loc;
  typechecker_.BeginFunction(func->decl.sig.result_types);
  CheckExprList(loc, func->exprs);
  typechecker_.EndFunction();
  current_func_ = nullptr;
}

void Validator::PrintConstExprError(const Location* loc, const char* desc) {
  PrintError(loc,
             "invalid %s, must be a constant expression; either *.const or "
             "global.get.",
             desc);
}

void Validator::CheckConstInitExpr(const Location* loc,
                                   const ExprList& exprs,
                                   Type expected_type,
                                   const char* desc) {
  Type type = Type::Void;
  if (!exprs.empty()) {
    if (exprs.size() > 1) {
      PrintConstExprError(loc, desc);
      return;
    }

    const Expr* expr = &exprs.front();
    loc = &expr->loc;

    switch (expr->type()) {
      case ExprType::Const:
        type = cast<ConstExpr>(expr)->const_.type;
        break;

      case ExprType::GlobalGet: {
        const Global* ref_global = nullptr;
        Index ref_global_index;
        if (Failed(CheckGlobalVar(&cast<GlobalGetExpr>(expr)->var, &ref_global,
                                  &ref_global_index))) {
          return;
        }

        type = ref_global->type;
        if (ref_global_index >= num_imported_globals_) {
          PrintError(
              loc,
              "initializer expression can only reference an imported global");
        }

        if (ref_global->mutable_) {
          PrintError(
              loc, "initializer expression cannot reference a mutable global");
        }
        break;
      }

      default:
        PrintConstExprError(loc, desc);
        return;
    }
  }

  CheckType(loc, type, expected_type, desc);
}

void Validator::CheckGlobal(const Location* loc, const Global* global) {
  CheckConstInitExpr(loc, global->init_expr, global->type,
                     "global initializer expression");
}

void Validator::CheckLimits(const Location* loc,
                            const Limits* limits,
                            uint64_t absolute_max,
                            const char* desc) {
  if (limits->initial > absolute_max) {
    PrintError(loc, "initial %s (%" PRIu64 ") must be <= (%" PRIu64 ")", desc,
               limits->initial, absolute_max);
  }

  if (limits->has_max) {
    if (limits->max > absolute_max) {
      PrintError(loc, "max %s (%" PRIu64 ") must be <= (%" PRIu64 ")", desc,
                 limits->max, absolute_max);
    }

    if (limits->max < limits->initial) {
      PrintError(loc,
                 "max %s (%" PRIu64 ") must be >= initial %s (%" PRIu64 ")",
                 desc, limits->max, desc, limits->initial);
    }
  }
}

void Validator::CheckTable(const Location* loc, const Table* table) {
  if (current_table_index_ == 1 &&
      !options_.features.reference_types_enabled()) {
    PrintError(loc, "only one table allowed");
  }
  CheckLimits(loc, &table->elem_limits, UINT32_MAX, "elems");

  if (table->elem_limits.is_shared) {
    PrintError(loc, "tables may not be shared");
  }
  if (table->elem_type == Type::Anyref &&
      !options_.features.reference_types_enabled()) {
    PrintError(loc, "tables must have anyref type");
  }
  if (table->elem_type != Type::Anyref && table->elem_type != Type::Funcref) {
    PrintError(loc, "tables must have anyref or funcref type");
  }
}

void Validator::CheckElemSegments(const Module* module) {
  for (const ModuleField& field : module->fields) {
    if (auto elem_segment_field = dyn_cast<ElemSegmentModuleField>(&field)) {
      auto&& elem_segment = elem_segment_field->elem_segment;
      const Table* table;
      for (const Var& var : elem_segment.vars) {
        CheckFuncVar(&var, nullptr);
      }

      if (elem_segment.passive)  {
        continue;
      }
      if (Failed(CheckTableVar(&elem_segment.table_var, &table))) {
        continue;
      }
      CheckConstInitExpr(&field.loc, elem_segment.offset, Type::I32,
                         "elem segment offset");
    }
  }
}

void Validator::CheckMemory(const Location* loc, const Memory* memory) {
  if (current_memory_index_ == 1) {
    PrintError(loc, "only one memory block allowed");
  }
  CheckLimits(loc, &memory->page_limits, WABT_MAX_PAGES, "pages");

  if (memory->page_limits.is_shared) {
    if (!options_.features.threads_enabled()) {
      PrintError(loc, "memories may not be shared");
    } else if (!memory->page_limits.has_max) {
      PrintError(loc, "shared memories must have max sizes");
    }
  }
}

void Validator::CheckDataSegments(const Module* module) {
  for (const ModuleField& field : module->fields) {
    if (auto data_segment_field = dyn_cast<DataSegmentModuleField>(&field)) {
      auto&& data_segment = data_segment_field->data_segment;
      const Memory* memory;
      if (data_segment.passive)  {
        continue;
      }
      if (Failed(CheckMemoryVar(&data_segment.memory_var, &memory))) {
        continue;
      }
      CheckConstInitExpr(&field.loc, data_segment.offset, Type::I32,
                         "data segment offset");
    }
  }
}

void Validator::CheckImport(const Location* loc, const Import* import) {
  switch (import->kind()) {
    case ExternalKind::Event:
      ++current_event_index_;
      CheckEvent(loc, &cast<EventImport>(import)->event);
      break;

    case ExternalKind::Func: {
      auto* func_import = cast<FuncImport>(import);
      if (func_import->func.decl.has_func_type) {
        CheckFuncTypeVar(&func_import->func.decl.type_var, nullptr);
      }
      break;
    }

    case ExternalKind::Table:
      CheckTable(loc, &cast<TableImport>(import)->table);
      ++current_table_index_;
      break;

    case ExternalKind::Memory:
      CheckMemory(loc, &cast<MemoryImport>(import)->memory);
      ++current_memory_index_;
      break;

    case ExternalKind::Global: {
      auto* global_import = cast<GlobalImport>(import);
      if (global_import->global.mutable_ &&
          !options_.features.mutable_globals_enabled()) {
        PrintError(loc, "mutable globals cannot be imported");
      }
      ++num_imported_globals_;
      ++current_global_index_;
      break;
    }
  }
}

void Validator::CheckExport(const Location* loc, const Export* export_) {
  switch (export_->kind) {
    case ExternalKind::Event:
      CheckEventVar(&export_->var, nullptr);
      break;
    case ExternalKind::Func:
      CheckFuncVar(&export_->var, nullptr);
      break;
    case ExternalKind::Table:
      CheckTableVar(&export_->var, nullptr);
      break;
    case ExternalKind::Memory:
      CheckMemoryVar(&export_->var, nullptr);
      break;
    case ExternalKind::Global: {
      const Global* global;
      if (Succeeded(CheckGlobalVar(&export_->var, &global, nullptr))) {
        if (global->mutable_ && !options_.features.mutable_globals_enabled()) {
          PrintError(&export_->var.loc, "mutable globals cannot be exported");
        }
      }
      break;
    }
  }
}

void Validator::CheckDuplicateExportBindings(const Module* module) {
  module->export_bindings.FindDuplicates(
      [this](const BindingHash::value_type& a,
             const BindingHash::value_type& b) {
        // Choose the location that is later in the file.
        const Location& a_loc = a.second.loc;
        const Location& b_loc = b.second.loc;
        const Location& loc = a_loc.line > b_loc.line ? a_loc : b_loc;
        PrintError(&loc, "redefinition of export \"%s\"", a.first.c_str());
      });
}

Result Validator::CheckModule(const Module* module) {
  bool seen_start = false;

  current_module_ = module;
  current_table_index_ = 0;
  current_memory_index_ = 0;
  current_global_index_ = 0;
  num_imported_globals_ = 0;
  current_event_index_ = 0;

  for (const ModuleField& field : module->fields) {
    switch (field.type()) {
      case ModuleFieldType::Event:
        ++current_event_index_;
        CheckEvent(&field.loc, &cast<EventModuleField>(&field)->event);
        break;

      case ModuleFieldType::Func:
        CheckFunc(&field.loc, &cast<FuncModuleField>(&field)->func);
        break;

      case ModuleFieldType::Global:
        CheckGlobal(&field.loc, &cast<GlobalModuleField>(&field)->global);
        current_global_index_++;
        break;

      case ModuleFieldType::Import:
        CheckImport(&field.loc, cast<ImportModuleField>(&field)->import.get());
        break;

      case ModuleFieldType::Export:
        CheckExport(&field.loc, &cast<ExportModuleField>(&field)->export_);
        break;

      case ModuleFieldType::Table:
        CheckTable(&field.loc, &cast<TableModuleField>(&field)->table);
        current_table_index_++;
        break;

      case ModuleFieldType::ElemSegment:
        // Checked below.
        break;

      case ModuleFieldType::Memory:
        CheckMemory(&field.loc, &cast<MemoryModuleField>(&field)->memory);
        current_memory_index_++;
        break;

      case ModuleFieldType::DataSegment:
        // Checked below.
        break;

      case ModuleFieldType::FuncType:
        break;

      case ModuleFieldType::Start: {
        if (seen_start) {
          PrintError(&field.loc, "only one start function allowed");
        }

        const Func* start_func = nullptr;
        CheckFuncVar(&cast<StartModuleField>(&field)->start, &start_func);
        if (start_func) {
          if (start_func->GetNumParams() != 0) {
            PrintError(&field.loc, "start function must be nullary");
          }

          if (start_func->GetNumResults() != 0) {
            PrintError(&field.loc, "start function must not return anything");
          }
        }
        seen_start = true;
        break;
      }
    }
  }

  CheckElemSegments(module);
  CheckDataSegments(module);
  CheckDuplicateExportBindings(module);

  return result_;
}

// Returns the result type of the invoked function, checked by the caller;
// returning nullptr means that another error occured first, so the result type
// should be ignored.
const TypeVector* Validator::CheckInvoke(const InvokeAction* action) {
  const Module* module = script_->GetModule(action->module_var);
  if (!module) {
    PrintError(&action->loc, "unknown module");
    return nullptr;
  }

  const Export* export_ = module->GetExport(action->name);
  if (!export_) {
    PrintError(&action->loc, "unknown function export \"%s\"",
               action->name.c_str());
    return nullptr;
  }

  const Func* func = module->GetFunc(export_->var);
  if (!func) {
    // This error will have already been reported, just skip it.
    return nullptr;
  }

  size_t actual_args = action->args.size();
  size_t expected_args = func->GetNumParams();
  if (expected_args != actual_args) {
    PrintError(&action->loc,
               "too %s parameters to function. got %" PRIzd
               ", expected %" PRIzd,
               actual_args > expected_args ? "many" : "few", actual_args,
               expected_args);
    return nullptr;
  }
  for (size_t i = 0; i < actual_args; ++i) {
    const Const* const_ = &action->args[i];
    CheckTypeIndex(&const_->loc, const_->type, func->GetParamType(i), "invoke",
                   i, "argument");
  }

  return &func->decl.sig.result_types;
}

Result Validator::CheckGet(const GetAction* action, Type* out_type) {
  const Module* module = script_->GetModule(action->module_var);
  if (!module) {
    PrintError(&action->loc, "unknown module");
    return Result::Error;
  }

  const Export* export_ = module->GetExport(action->name);
  if (!export_) {
    PrintError(&action->loc, "unknown global export \"%s\"",
               action->name.c_str());
    return Result::Error;
  }

  const Global* global = module->GetGlobal(export_->var);
  if (!global) {
    // This error will have already been reported, just skip it.
    return Result::Error;
  }

  *out_type = global->type;
  return Result::Ok;
}

Result Validator::CheckEventVar(const Var* var, const Event** out_event) {
  Index index;
  CHECK_RESULT(CheckVar(current_module_->events.size(), var, "event", &index));
  if (out_event) {
    *out_event = current_module_->events[index];
  }
  return Result::Ok;
}

void Validator::CheckEvent(const Location* loc, const Event* event) {
  CheckFuncSignature(loc, event->decl);
  if (event->decl.sig.GetNumResults() > 0) {
    PrintError(loc, "Event signature must have 0 results.");
  }
}

Validator::ActionResult Validator::CheckAction(const Action* action) {
  ActionResult result;
  ZeroMemory(result);

  switch (action->type()) {
    case ActionType::Invoke:
      result.types = CheckInvoke(cast<InvokeAction>(action));
      result.kind =
          result.types ? ActionResult::Kind::Types : ActionResult::Kind::Error;
      break;

    case ActionType::Get:
      if (Succeeded(CheckGet(cast<GetAction>(action), &result.type))) {
        result.kind = ActionResult::Kind::Type;
      } else {
        result.kind = ActionResult::Kind::Error;
      }
      break;
  }

  return result;
}

void Validator::CheckAssertReturnNanCommand(const Action* action) {
  ActionResult result = CheckAction(action);

  // A valid result type will either be f32 or f64; convert a Types result into
  // a Type result, so it is easier to check below. Type::Any is used to
  // specify a type that should not be checked (because an earlier error
  // occurred).
  if (result.kind == ActionResult::Kind::Types) {
    if (result.types->size() == 1) {
      result.kind = ActionResult::Kind::Type;
      result.type = (*result.types)[0];
    } else {
      PrintError(&action->loc, "expected 1 result, got %" PRIzd,
                 result.types->size());
      result.type = Type::Any;
    }
  }

  if (result.kind == ActionResult::Kind::Type && result.type != Type::Any) {
    CheckAssertReturnNanType(&action->loc, result.type, "action");
  }
}

void Validator::CheckCommand(const Command* command) {
  switch (command->type) {
    case CommandType::Module:
      CheckModule(&cast<ModuleCommand>(command)->module);
      break;

    case CommandType::Action:
      // Ignore result type.
      CheckAction(cast<ActionCommand>(command)->action.get());
      break;

    case CommandType::Register:
    case CommandType::AssertMalformed:
    case CommandType::AssertInvalid:
    case CommandType::AssertUnlinkable:
    case CommandType::AssertUninstantiable:
      // Ignore.
      break;

    case CommandType::AssertReturn: {
      auto* assert_return_command = cast<AssertReturnCommand>(command);
      const Action* action = assert_return_command->action.get();
      ActionResult result = CheckAction(action);
      switch (result.kind) {
        case ActionResult::Kind::Types:
          CheckConstTypes(&action->loc, *result.types,
                          assert_return_command->expected, "action");
          break;

        case ActionResult::Kind::Type:
          CheckConstType(&action->loc, result.type,
                         assert_return_command->expected, "action");
          break;

        case ActionResult::Kind::Error:
          // Error occurred, don't do any further checks.
          break;
      }
      break;
    }

    case CommandType::AssertReturnCanonicalNan:
      CheckAssertReturnNanCommand(
          cast<AssertReturnCanonicalNanCommand>(command)->action.get());
      break;

    case CommandType::AssertReturnArithmeticNan:
      CheckAssertReturnNanCommand(
          cast<AssertReturnArithmeticNanCommand>(command)->action.get());
      break;

    case CommandType::AssertTrap:
      // ignore result type.
      CheckAction(cast<AssertTrapCommand>(command)->action.get());
      break;
    case CommandType::AssertExhaustion:
      // ignore result type.
      CheckAction(cast<AssertExhaustionCommand>(command)->action.get());
      break;
  }
}

Result Validator::CheckScript(const Script* script) {
  for (const std::unique_ptr<Command>& command : script->commands)
    CheckCommand(command.get());
  return result_;
}

class Validator::CheckFuncSignatureExprVisitorDelegate
    : public ExprVisitor::DelegateNop {
 public:
  explicit CheckFuncSignatureExprVisitorDelegate(Validator* validator)
      : validator_(validator) {}

  Result BeginBlockExpr(BlockExpr* expr) override {
    validator_->CheckBlockDeclaration(&expr->loc, Opcode::Block,
                                      &expr->block.decl);
    return Result::Ok;
  }

  Result OnCallIndirectExpr(CallIndirectExpr* expr) override {
    validator_->CheckFuncSignature(&expr->loc, expr->decl);
    return Result::Ok;
  }

  Result OnReturnCallIndirectExpr(ReturnCallIndirectExpr* expr) override {
    validator_->CheckFuncSignature(&expr->loc, expr->decl);
    return Result::Ok;
  }

  Result BeginIfExpr(IfExpr* expr) override {
    validator_->CheckBlockDeclaration(&expr->loc, Opcode::If,
                                      &expr->true_.decl);
    return Result::Ok;
  }

  Result BeginLoopExpr(LoopExpr* expr) override {
    validator_->CheckBlockDeclaration(&expr->loc, Opcode::Loop,
                                      &expr->block.decl);
    return Result::Ok;
  }

  Result BeginTryExpr(TryExpr* expr) override {
    validator_->CheckBlockDeclaration(&expr->loc, Opcode::Try,
                                      &expr->block.decl);
    return Result::Ok;
  }

 private:
  Validator* validator_;
};

Result Validator::CheckAllFuncSignatures(const Module* module) {
  current_module_ = module;
  for (const ModuleField& field : module->fields) {
    switch (field.type()) {
      case ModuleFieldType::Func: {
        auto func_field = cast<FuncModuleField>(&field);
        CheckFuncSignature(&field.loc, func_field->func.decl);
        CheckFuncSignatureExprVisitorDelegate delegate(this);
        ExprVisitor visitor(&delegate);
        // TODO(binji): would rather not do a const_cast here, but the visitor
        // is non-const only.
        visitor.VisitFunc(const_cast<Func*>(&func_field->func));
        break;
      }

      default:
        break;
    }
  }
  return result_;
}

}  // end anonymous namespace

Result ValidateScript(const Script* script,
                      Errors* errors,
                      const ValidateOptions& options) {
  Validator validator(errors, script, options);

  return validator.CheckScript(script);
}

Result ValidateModule(const Module* module,
                      Errors* errors,
                      const ValidateOptions& options) {
  Validator validator(errors, nullptr, options);

  return validator.CheckModule(module);
}

Result ValidateFuncSignatures(const Module* module,
                              Errors* errors,
                              const ValidateOptions& options) {
  Validator validator(errors, nullptr, options);

  return validator.CheckAllFuncSignatures(module);
}

}  // namespace wabt