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diff --git a/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp
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+//===--- NarrowingConversionsCheck.cpp - clang-tidy------------------------===//
+//
+// 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 "NarrowingConversionsCheck.h"
+#include "../utils/OptionsUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/Type.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "llvm/ADT/APSInt.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+
+#include <cstdint>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+AST_MATCHER_P(QualType, hasAnyType, std::vector<StringRef>, Names) {
+  if (Names.empty())
+    return false;
+
+  std::string Name = Node.getLocalUnqualifiedType().getAsString();
+  return llvm::any_of(Names, [&Name](StringRef Ref) { return Ref == Name; });
+}
+
+AST_MATCHER(FieldDecl, hasIntBitwidth) {
+  assert(Node.isBitField());
+  const ASTContext &Ctx = Node.getASTContext();
+  unsigned IntBitWidth = Ctx.getIntWidth(Ctx.IntTy);
+  unsigned CurrentBitWidth = Node.getBitWidthValue(Ctx);
+  return IntBitWidth == CurrentBitWidth;
+}
+
+} // namespace
+
+NarrowingConversionsCheck::NarrowingConversionsCheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      WarnOnIntegerNarrowingConversion(
+          Options.get("WarnOnIntegerNarrowingConversion", true)),
+      WarnOnIntegerToFloatingPointNarrowingConversion(
+          Options.get("WarnOnIntegerToFloatingPointNarrowingConversion", true)),
+      WarnOnFloatingPointNarrowingConversion(
+          Options.get("WarnOnFloatingPointNarrowingConversion", true)),
+      WarnWithinTemplateInstantiation(
+          Options.get("WarnWithinTemplateInstantiation", false)),
+      WarnOnEquivalentBitWidth(Options.get("WarnOnEquivalentBitWidth", true)),
+      IgnoreConversionFromTypes(Options.get("IgnoreConversionFromTypes", "")),
+      PedanticMode(Options.get("PedanticMode", false)) {}
+
+void NarrowingConversionsCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "WarnOnIntegerNarrowingConversion",
+                WarnOnIntegerNarrowingConversion);
+  Options.store(Opts, "WarnOnIntegerToFloatingPointNarrowingConversion",
+                WarnOnIntegerToFloatingPointNarrowingConversion);
+  Options.store(Opts, "WarnOnFloatingPointNarrowingConversion",
+                WarnOnFloatingPointNarrowingConversion);
+  Options.store(Opts, "WarnWithinTemplateInstantiation",
+                WarnWithinTemplateInstantiation);
+  Options.store(Opts, "WarnOnEquivalentBitWidth", WarnOnEquivalentBitWidth);
+  Options.store(Opts, "IgnoreConversionFromTypes", IgnoreConversionFromTypes);
+  Options.store(Opts, "PedanticMode", PedanticMode);
+}
+
+void NarrowingConversionsCheck::registerMatchers(MatchFinder *Finder) {
+  // ceil() and floor() are guaranteed to return integers, even though the type
+  // is not integral.
+  const auto IsCeilFloorCallExpr = expr(callExpr(callee(functionDecl(
+      hasAnyName("::ceil", "::std::ceil", "::floor", "::std::floor")))));
+
+  std::vector<StringRef> IgnoreConversionFromTypesVec =
+      utils::options::parseStringList(IgnoreConversionFromTypes);
+
+  // We may want to exclude other types from the checks, such as `size_type`
+  // and `difference_type`. These are often used to count elements, represented
+  // in 64 bits and assigned to `int`. Rarely are people counting >2B elements.
+  const auto IsConversionFromIgnoredType =
+      anyOf(hasType(namedDecl(hasAnyName(IgnoreConversionFromTypesVec))),
+            allOf(unless(hasType(namedDecl())),
+                  hasType(qualType(hasAnyType(IgnoreConversionFromTypesVec)))));
+
+  // `IsConversionFromIgnoredType` will ignore narrowing calls from those types,
+  // but not expressions that are promoted to an ignored type as a result of a
+  // binary expression with one of those types.
+  // For example, it will continue to reject:
+  // `int narrowed = int_value + container.size()`.
+  // We attempt to address common incidents of compound expressions with
+  // `IsIgnoredTypeTwoLevelsDeep`, allowing binary expressions that have one
+  // operand of the ignored types and the other operand of another integer type.
+  const auto IsIgnoredTypeTwoLevelsDeep =
+      anyOf(IsConversionFromIgnoredType,
+            binaryOperator(hasOperands(IsConversionFromIgnoredType,
+                                       hasType(isInteger()))));
+
+  // Bitfields are special. Due to integral promotion [conv.prom/5] bitfield
+  // member access expressions are frequently wrapped by an implicit cast to
+  // `int` if that type can represent all the values of the bitfield.
+  //
+  // Consider these examples:
+  //   struct SmallBitfield { unsigned int id : 4; };
+  //   x.id & 1;             (case-1)
+  //   x.id & 1u;            (case-2)
+  //   x.id << 1u;           (case-3)
+  //   (unsigned)x.id << 1;  (case-4)
+  //
+  // Due to the promotion rules, we would get a warning for case-1. It's
+  // debatable how useful this is, but the user at least has a convenient way of
+  // //fixing// it by adding the `u` unsigned-suffix to the literal as
+  // demonstrated by case-2. However, this won't work for shift operators like
+  // the one in case-3. In case of a normal binary operator, both operands
+  // contribute to the result type. However, the type of the shift expression is
+  // the promoted type of the left operand. One could still suppress this
+  // superfluous warning by explicitly casting the bitfield member access as
+  // case-4 demonstrates, but why? The compiler already knew that the value from
+  // the member access should safely fit into an `int`, why do we have this
+  // warning in the first place? So, hereby we suppress this specific scenario.
+  //
+  // Note that the bitshift operation might invoke unspecified/undefined
+  // behavior, but that's another topic, this checker is about detecting
+  // conversion-related defects.
+  //
+  // Example AST for `x.id << 1`:
+  //   BinaryOperator 'int' '<<'
+  //   |-ImplicitCastExpr 'int' <IntegralCast>
+  //   | `-ImplicitCastExpr 'unsigned int' <LValueToRValue>
+  //   |   `-MemberExpr 'unsigned int' lvalue bitfield .id
+  //   |     `-DeclRefExpr 'SmallBitfield' lvalue ParmVar 'x' 'SmallBitfield'
+  //   `-IntegerLiteral 'int' 1
+  const auto ImplicitIntWidenedBitfieldValue = implicitCastExpr(
+      hasCastKind(CK_IntegralCast), hasType(asString("int")),
+      has(castExpr(hasCastKind(CK_LValueToRValue),
+                   has(ignoringParens(memberExpr(hasDeclaration(
+                       fieldDecl(isBitField(), unless(hasIntBitwidth())))))))));
+
+  // Casts:
+  //   i = 0.5;
+  //   void f(int); f(0.5);
+  Finder->addMatcher(
+      traverse(TK_AsIs, implicitCastExpr(
+                            hasImplicitDestinationType(
+                                hasUnqualifiedDesugaredType(builtinType())),
+                            hasSourceExpression(hasType(
+                                hasUnqualifiedDesugaredType(builtinType()))),
+                            unless(hasSourceExpression(IsCeilFloorCallExpr)),
+                            unless(hasParent(castExpr())),
+                            WarnWithinTemplateInstantiation
+                                ? stmt()
+                                : stmt(unless(isInTemplateInstantiation())),
+                            IgnoreConversionFromTypes.empty()
+                                ? castExpr()
+                                : castExpr(unless(hasSourceExpression(
+                                      IsIgnoredTypeTwoLevelsDeep))),
+                            unless(ImplicitIntWidenedBitfieldValue))
+                            .bind("cast")),
+      this);
+
+  // Binary operators:
+  //   i += 0.5;
+  Finder->addMatcher(
+      binaryOperator(
+          isAssignmentOperator(),
+          hasLHS(expr(hasType(hasUnqualifiedDesugaredType(builtinType())))),
+          hasRHS(expr(hasType(hasUnqualifiedDesugaredType(builtinType())))),
+          unless(hasRHS(IsCeilFloorCallExpr)),
+          WarnWithinTemplateInstantiation
+              ? binaryOperator()
+              : binaryOperator(unless(isInTemplateInstantiation())),
+          IgnoreConversionFromTypes.empty()
+              ? binaryOperator()
+              : binaryOperator(unless(hasRHS(IsIgnoredTypeTwoLevelsDeep))),
+          // The `=` case generates an implicit cast
+          // which is covered by the previous matcher.
+          unless(hasOperatorName("=")))
+          .bind("binary_op"),
+      this);
+}
+
+static const BuiltinType *getBuiltinType(const Expr &E) {
+  return E.getType().getCanonicalType().getTypePtr()->getAs<BuiltinType>();
+}
+
+static QualType getUnqualifiedType(const Expr &E) {
+  return E.getType().getUnqualifiedType();
+}
+
+static APValue getConstantExprValue(const ASTContext &Ctx, const Expr &E) {
+  if (auto IntegerConstant = E.getIntegerConstantExpr(Ctx))
+    return APValue(*IntegerConstant);
+  APValue Constant;
+  if (Ctx.getLangOpts().CPlusPlus && E.isCXX11ConstantExpr(Ctx, &Constant))
+    return Constant;
+  return {};
+}
+
+static bool getIntegerConstantExprValue(const ASTContext &Context,
+                                        const Expr &E, llvm::APSInt &Value) {
+  APValue Constant = getConstantExprValue(Context, E);
+  if (!Constant.isInt())
+    return false;
+  Value = Constant.getInt();
+  return true;
+}
+
+static bool getFloatingConstantExprValue(const ASTContext &Context,
+                                         const Expr &E, llvm::APFloat &Value) {
+  APValue Constant = getConstantExprValue(Context, E);
+  if (!Constant.isFloat())
+    return false;
+  Value = Constant.getFloat();
+  return true;
+}
+
+namespace {
+
+struct IntegerRange {
+  bool contains(const IntegerRange &From) const {
+    return llvm::APSInt::compareValues(Lower, From.Lower) <= 0 &&
+           llvm::APSInt::compareValues(Upper, From.Upper) >= 0;
+  }
+
+  bool contains(const llvm::APSInt &Value) const {
+    return llvm::APSInt::compareValues(Lower, Value) <= 0 &&
+           llvm::APSInt::compareValues(Upper, Value) >= 0;
+  }
+
+  llvm::APSInt Lower;
+  llvm::APSInt Upper;
+};
+
+} // namespace
+
+static IntegerRange createFromType(const ASTContext &Context,
+                                   const BuiltinType &T) {
+  if (T.isFloatingPoint()) {
+    unsigned PrecisionBits = llvm::APFloatBase::semanticsPrecision(
+        Context.getFloatTypeSemantics(T.desugar()));
+    // Contrary to two's complement integer, floating point values are
+    // symmetric and have the same number of positive and negative values.
+    // The range of valid integers for a floating point value is:
+    // [-2^PrecisionBits, 2^PrecisionBits]
+
+    // Values are created with PrecisionBits plus two bits:
+    // - One to express the missing negative value of 2's complement
+    //   representation.
+    // - One for the sign.
+    llvm::APSInt UpperValue(PrecisionBits + 2, /*isUnsigned*/ false);
+    UpperValue.setBit(PrecisionBits);
+    llvm::APSInt LowerValue(PrecisionBits + 2, /*isUnsigned*/ false);
+    LowerValue.setBit(PrecisionBits);
+    LowerValue.setSignBit();
+    return {LowerValue, UpperValue};
+  }
+  assert(T.isInteger() && "Unexpected builtin type");
+  uint64_t TypeSize = Context.getTypeSize(&T);
+  bool IsUnsignedInteger = T.isUnsignedInteger();
+  return {llvm::APSInt::getMinValue(TypeSize, IsUnsignedInteger),
+          llvm::APSInt::getMaxValue(TypeSize, IsUnsignedInteger)};
+}
+
+static bool isWideEnoughToHold(const ASTContext &Context,
+                               const BuiltinType &FromType,
+                               const BuiltinType &ToType) {
+  IntegerRange FromIntegerRange = createFromType(Context, FromType);
+  IntegerRange ToIntegerRange = createFromType(Context, ToType);
+  return ToIntegerRange.contains(FromIntegerRange);
+}
+
+static bool isWideEnoughToHold(const ASTContext &Context,
+                               const llvm::APSInt &IntegerConstant,
+                               const BuiltinType &ToType) {
+  IntegerRange ToIntegerRange = createFromType(Context, ToType);
+  return ToIntegerRange.contains(IntegerConstant);
+}
+
+// Returns true iff the floating point constant can be losslessly represented
+// by an integer in the given destination type. eg. 2.0 can be accurately
+// represented by an int32_t, but neither 2^33 nor 2.001 can.
+static bool isFloatExactlyRepresentable(const ASTContext &Context,
+                                        const llvm::APFloat &FloatConstant,
+                                        const QualType &DestType) {
+  unsigned DestWidth = Context.getIntWidth(DestType);
+  bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
+  llvm::APSInt Result = llvm::APSInt(DestWidth, !DestSigned);
+  bool IsExact = false;
+  bool Overflows = FloatConstant.convertToInteger(
+                       Result, llvm::APFloat::rmTowardZero, &IsExact) &
+                   llvm::APFloat::opInvalidOp;
+  return !Overflows && IsExact;
+}
+
+static llvm::SmallString<64> getValueAsString(const llvm::APSInt &Value,
+                                              uint64_t HexBits) {
+  llvm::SmallString<64> Str;
+  Value.toString(Str, 10);
+  if (HexBits > 0) {
+    Str.append(" (0x");
+    llvm::SmallString<32> HexValue;
+    Value.toStringUnsigned(HexValue, 16);
+    for (size_t I = HexValue.size(); I < (HexBits / 4); ++I)
+      Str.append("0");
+    Str.append(HexValue);
+    Str.append(")");
+  }
+  return Str;
+}
+
+bool NarrowingConversionsCheck::isWarningInhibitedByEquivalentSize(
+    const ASTContext &Context, const BuiltinType &FromType,
+    const BuiltinType &ToType) const {
+  // With this option, we don't warn on conversions that have equivalent width
+  // in bits. eg. uint32 <-> int32.
+  if (!WarnOnEquivalentBitWidth) {
+    uint64_t FromTypeSize = Context.getTypeSize(&FromType);
+    uint64_t ToTypeSize = Context.getTypeSize(&ToType);
+    if (FromTypeSize == ToTypeSize) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void NarrowingConversionsCheck::diagNarrowType(SourceLocation SourceLoc,
+                                               const Expr &Lhs,
+                                               const Expr &Rhs) {
+  diag(SourceLoc, "narrowing conversion from %0 to %1")
+      << getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
+}
+
+void NarrowingConversionsCheck::diagNarrowTypeToSignedInt(
+    SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs) {
+  diag(SourceLoc, "narrowing conversion from %0 to signed type %1 is "
+                  "implementation-defined")
+      << getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
+}
+
+void NarrowingConversionsCheck::diagNarrowIntegerConstant(
+    SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs,
+    const llvm::APSInt &Value) {
+  diag(SourceLoc,
+       "narrowing conversion from constant value %0 of type %1 to %2")
+      << getValueAsString(Value, /*NoHex*/ 0) << getUnqualifiedType(Rhs)
+      << getUnqualifiedType(Lhs);
+}
+
+void NarrowingConversionsCheck::diagNarrowIntegerConstantToSignedInt(
+    SourceLocation SourceLoc, const Expr &Lhs, const Expr &Rhs,
+    const llvm::APSInt &Value, const uint64_t HexBits) {
+  diag(SourceLoc, "narrowing conversion from constant value %0 of type %1 "
+                  "to signed type %2 is implementation-defined")
+      << getValueAsString(Value, HexBits) << getUnqualifiedType(Rhs)
+      << getUnqualifiedType(Lhs);
+}
+
+void NarrowingConversionsCheck::diagNarrowConstant(SourceLocation SourceLoc,
+                                                   const Expr &Lhs,
+                                                   const Expr &Rhs) {
+  diag(SourceLoc, "narrowing conversion from constant %0 to %1")
+      << getUnqualifiedType(Rhs) << getUnqualifiedType(Lhs);
+}
+
+void NarrowingConversionsCheck::diagConstantCast(SourceLocation SourceLoc,
+                                                 const Expr &Lhs,
+                                                 const Expr &Rhs) {
+  diag(SourceLoc, "constant value should be of type of type %0 instead of %1")
+      << getUnqualifiedType(Lhs) << getUnqualifiedType(Rhs);
+}
+
+void NarrowingConversionsCheck::diagNarrowTypeOrConstant(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  APValue Constant = getConstantExprValue(Context, Rhs);
+  if (Constant.isInt())
+    return diagNarrowIntegerConstant(SourceLoc, Lhs, Rhs, Constant.getInt());
+  if (Constant.isFloat())
+    return diagNarrowConstant(SourceLoc, Lhs, Rhs);
+  return diagNarrowType(SourceLoc, Lhs, Rhs);
+}
+
+void NarrowingConversionsCheck::handleIntegralCast(const ASTContext &Context,
+                                                   SourceLocation SourceLoc,
+                                                   const Expr &Lhs,
+                                                   const Expr &Rhs) {
+  if (WarnOnIntegerNarrowingConversion) {
+    const BuiltinType *ToType = getBuiltinType(Lhs);
+    // From [conv.integral]p7.3.8:
+    // Conversions to unsigned integer is well defined so no warning is issued.
+    // "The resulting value is the smallest unsigned value equal to the source
+    // value modulo 2^n where n is the number of bits used to represent the
+    // destination type."
+    if (ToType->isUnsignedInteger())
+      return;
+    const BuiltinType *FromType = getBuiltinType(Rhs);
+
+    // With this option, we don't warn on conversions that have equivalent width
+    // in bits. eg. uint32 <-> int32.
+    if (!WarnOnEquivalentBitWidth) {
+      uint64_t FromTypeSize = Context.getTypeSize(FromType);
+      uint64_t ToTypeSize = Context.getTypeSize(ToType);
+      if (FromTypeSize == ToTypeSize)
+        return;
+    }
+
+    llvm::APSInt IntegerConstant;
+    if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
+      if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
+        diagNarrowIntegerConstantToSignedInt(SourceLoc, Lhs, Rhs,
+                                             IntegerConstant,
+                                             Context.getTypeSize(FromType));
+      return;
+    }
+    if (!isWideEnoughToHold(Context, *FromType, *ToType))
+      diagNarrowTypeToSignedInt(SourceLoc, Lhs, Rhs);
+  }
+}
+
+void NarrowingConversionsCheck::handleIntegralToBoolean(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  // Conversion from Integral to Bool value is well defined.
+
+  // We keep this function (even if it is empty) to make sure that
+  // handleImplicitCast and handleBinaryOperator are symmetric in their behavior
+  // and handle the same cases.
+}
+
+void NarrowingConversionsCheck::handleIntegralToFloating(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  if (WarnOnIntegerToFloatingPointNarrowingConversion) {
+    const BuiltinType *ToType = getBuiltinType(Lhs);
+    llvm::APSInt IntegerConstant;
+    if (getIntegerConstantExprValue(Context, Rhs, IntegerConstant)) {
+      if (!isWideEnoughToHold(Context, IntegerConstant, *ToType))
+        diagNarrowIntegerConstant(SourceLoc, Lhs, Rhs, IntegerConstant);
+      return;
+    }
+
+    const BuiltinType *FromType = getBuiltinType(Rhs);
+    if (isWarningInhibitedByEquivalentSize(Context, *FromType, *ToType))
+      return;
+    if (!isWideEnoughToHold(Context, *FromType, *ToType))
+      diagNarrowType(SourceLoc, Lhs, Rhs);
+  }
+}
+
+void NarrowingConversionsCheck::handleFloatingToIntegral(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  llvm::APFloat FloatConstant(0.0);
+  if (getFloatingConstantExprValue(Context, Rhs, FloatConstant)) {
+    if (!isFloatExactlyRepresentable(Context, FloatConstant, Lhs.getType()))
+      return diagNarrowConstant(SourceLoc, Lhs, Rhs);
+
+    if (PedanticMode)
+      return diagConstantCast(SourceLoc, Lhs, Rhs);
+
+    return;
+  }
+
+  const BuiltinType *FromType = getBuiltinType(Rhs);
+  const BuiltinType *ToType = getBuiltinType(Lhs);
+  if (isWarningInhibitedByEquivalentSize(Context, *FromType, *ToType))
+    return;
+  diagNarrowType(SourceLoc, Lhs, Rhs); // Assumed always lossy.
+}
+
+void NarrowingConversionsCheck::handleFloatingToBoolean(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  return diagNarrowTypeOrConstant(Context, SourceLoc, Lhs, Rhs);
+}
+
+void NarrowingConversionsCheck::handleBooleanToSignedIntegral(
+    const ASTContext &Context, SourceLocation SourceLoc, const Expr &Lhs,
+    const Expr &Rhs) {
+  // Conversion from Bool to SignedIntegral value is well defined.
+
+  // We keep this function (even if it is empty) to make sure that
+  // handleImplicitCast and handleBinaryOperator are symmetric in their behavior
+  // and handle the same cases.
+}
+
+void NarrowingConversionsCheck::handleFloatingCast(const ASTContext &Context,
+                                                   SourceLocation SourceLoc,
+                                                   const Expr &Lhs,
+                                                   const Expr &Rhs) {
+  if (WarnOnFloatingPointNarrowingConversion) {
+    const BuiltinType *ToType = getBuiltinType(Lhs);
+    APValue Constant = getConstantExprValue(Context, Rhs);
+    if (Constant.isFloat()) {
+      // From [dcl.init.list]p7.2:
+      // Floating point constant narrowing only takes place when the value is
+      // not within destination range. We convert the value to the destination
+      // type and check if the resulting value is infinity.
+      llvm::APFloat Tmp = Constant.getFloat();
+      bool UnusedLosesInfo = false;
+      Tmp.convert(Context.getFloatTypeSemantics(ToType->desugar()),
+                  llvm::APFloatBase::rmNearestTiesToEven, &UnusedLosesInfo);
+      if (Tmp.isInfinity())
+        diagNarrowConstant(SourceLoc, Lhs, Rhs);
+      return;
+    }
+    const BuiltinType *FromType = getBuiltinType(Rhs);
+    if (ToType->getKind() < FromType->getKind())
+      diagNarrowType(SourceLoc, Lhs, Rhs);
+  }
+}
+
+void NarrowingConversionsCheck::handleBinaryOperator(const ASTContext &Context,
+                                                     SourceLocation SourceLoc,
+                                                     const Expr &Lhs,
+                                                     const Expr &Rhs) {
+  assert(!Lhs.isInstantiationDependent() && !Rhs.isInstantiationDependent() &&
+         "Dependent types must be check before calling this function");
+  const BuiltinType *LhsType = getBuiltinType(Lhs);
+  const BuiltinType *RhsType = getBuiltinType(Rhs);
+  if (RhsType == nullptr || LhsType == nullptr)
+    return;
+  if (LhsType == RhsType)
+    return;
+  if (RhsType->getKind() == BuiltinType::Bool && LhsType->isSignedInteger())
+    return handleBooleanToSignedIntegral(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isInteger() && LhsType->getKind() == BuiltinType::Bool)
+    return handleIntegralToBoolean(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isInteger() && LhsType->isFloatingPoint())
+    return handleIntegralToFloating(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isInteger() && LhsType->isInteger())
+    return handleIntegralCast(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isFloatingPoint() && LhsType->getKind() == BuiltinType::Bool)
+    return handleFloatingToBoolean(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isFloatingPoint() && LhsType->isInteger())
+    return handleFloatingToIntegral(Context, SourceLoc, Lhs, Rhs);
+  if (RhsType->isFloatingPoint() && LhsType->isFloatingPoint())
+    return handleFloatingCast(Context, SourceLoc, Lhs, Rhs);
+}
+
+bool NarrowingConversionsCheck::handleConditionalOperator(
+    const ASTContext &Context, const Expr &Lhs, const Expr &Rhs) {
+  if (const auto *CO = llvm::dyn_cast<ConditionalOperator>(&Rhs)) {
+    // We have an expression like so: `output = cond ? lhs : rhs`
+    // From the point of view of narrowing conversion we treat it as two
+    // expressions `output = lhs` and `output = rhs`.
+    handleBinaryOperator(Context, CO->getLHS()->getExprLoc(), Lhs,
+                         *CO->getLHS());
+    handleBinaryOperator(Context, CO->getRHS()->getExprLoc(), Lhs,
+                         *CO->getRHS());
+    return true;
+  }
+  return false;
+}
+
+void NarrowingConversionsCheck::handleImplicitCast(
+    const ASTContext &Context, const ImplicitCastExpr &Cast) {
+  if (Cast.getExprLoc().isMacroID())
+    return;
+  const Expr &Lhs = Cast;
+  const Expr &Rhs = *Cast.getSubExpr();
+  if (Lhs.isInstantiationDependent() || Rhs.isInstantiationDependent())
+    return;
+  if (getBuiltinType(Lhs) == getBuiltinType(Rhs))
+    return;
+  if (handleConditionalOperator(Context, Lhs, Rhs))
+    return;
+  SourceLocation SourceLoc = Lhs.getExprLoc();
+  switch (Cast.getCastKind()) {
+  case CK_BooleanToSignedIntegral:
+    return handleBooleanToSignedIntegral(Context, SourceLoc, Lhs, Rhs);
+  case CK_IntegralToBoolean:
+    return handleIntegralToBoolean(Context, SourceLoc, Lhs, Rhs);
+  case CK_IntegralToFloating:
+    return handleIntegralToFloating(Context, SourceLoc, Lhs, Rhs);
+  case CK_IntegralCast:
+    return handleIntegralCast(Context, SourceLoc, Lhs, Rhs);
+  case CK_FloatingToBoolean:
+    return handleFloatingToBoolean(Context, SourceLoc, Lhs, Rhs);
+  case CK_FloatingToIntegral:
+    return handleFloatingToIntegral(Context, SourceLoc, Lhs, Rhs);
+  case CK_FloatingCast:
+    return handleFloatingCast(Context, SourceLoc, Lhs, Rhs);
+  default:
+    break;
+  }
+}
+
+void NarrowingConversionsCheck::handleBinaryOperator(const ASTContext &Context,
+                                                     const BinaryOperator &Op) {
+  if (Op.getBeginLoc().isMacroID())
+    return;
+  const Expr &Lhs = *Op.getLHS();
+  const Expr &Rhs = *Op.getRHS();
+  if (Lhs.isInstantiationDependent() || Rhs.isInstantiationDependent())
+    return;
+  if (handleConditionalOperator(Context, Lhs, Rhs))
+    return;
+  handleBinaryOperator(Context, Rhs.getBeginLoc(), Lhs, Rhs);
+}
+
+void NarrowingConversionsCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *Op = Result.Nodes.getNodeAs<BinaryOperator>("binary_op"))
+    return handleBinaryOperator(*Result.Context, *Op);
+  if (const auto *Cast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast"))
+    return handleImplicitCast(*Result.Context, *Cast);
+  llvm_unreachable("must be binary operator or cast expression");
+}
+} // namespace clang::tidy::bugprone