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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef frontend_ParseContext_h
#define frontend_ParseContext_h

#include "ds/Nestable.h"

#include "frontend/BytecodeCompiler.h"
#include "frontend/ErrorReporter.h"
#include "frontend/SharedContext.h"

namespace js {

namespace frontend {

class ParserBase;

// A data structure for tracking used names per parsing session in order to
// compute which bindings are closed over. Scripts and scopes are numbered
// monotonically in textual order and name uses are tracked by lists of
// (script id, scope id) pairs of their use sites.
//
// Intuitively, in a pair (P,S), P tracks the most nested function that has a
// use of u, and S tracks the most nested scope that is still being parsed.
//
// P is used to answer the question "is u used by a nested function?"
// S is used to answer the question "is u used in any scopes currently being
//                                   parsed?"
//
// The algorithm:
//
// Let Used by a map of names to lists.
//
// 1. Number all scopes in monotonic increasing order in textual order.
// 2. Number all scripts in monotonic increasing order in textual order.
// 3. When an identifier u is used in scope numbered S in script numbered P,
//    and u is found in Used,
//   a. Append (P,S) to Used[u].
//   b. Otherwise, assign the the list [(P,S)] to Used[u].
// 4. When we finish parsing a scope S in script P, for each declared name d in
//    Declared(S):
//   a. If d is found in Used, mark d as closed over if there is a value
//     (P_d, S_d) in Used[d] such that P_d > P and S_d > S.
//   b. Remove all values (P_d, S_d) in Used[d] such that S_d are >= S.
//
// Steps 1 and 2 are implemented by UsedNameTracker::next{Script,Scope}Id.
// Step 3 is implemented by UsedNameTracker::noteUsedInScope.
// Step 4 is implemented by UsedNameTracker::noteBoundInScope and
// Parser::propagateFreeNamesAndMarkClosedOverBindings.
class UsedNameTracker
{
  public:
    struct Use
    {
        uint32_t scriptId;
        uint32_t scopeId;
    };

    class UsedNameInfo
    {
        friend class UsedNameTracker;

        Vector<Use, 6> uses_;

        void resetToScope(uint32_t scriptId, uint32_t scopeId);

      public:
        explicit UsedNameInfo(JSContext* cx)
          : uses_(cx)
        { }

        UsedNameInfo(UsedNameInfo&& other)
          : uses_(std::move(other.uses_))
        { }

        bool noteUsedInScope(uint32_t scriptId, uint32_t scopeId) {
            if (uses_.empty() || uses_.back().scopeId < scopeId)
                return uses_.append(Use { scriptId, scopeId });
            return true;
        }

        void noteBoundInScope(uint32_t scriptId, uint32_t scopeId, bool* closedOver) {
            *closedOver = false;
            while (!uses_.empty()) {
                Use& innermost = uses_.back();
                if (innermost.scopeId < scopeId)
                    break;
                if (innermost.scriptId > scriptId)
                    *closedOver = true;
                uses_.popBack();
            }
        }

        bool isUsedInScript(uint32_t scriptId) const {
            return !uses_.empty() && uses_.back().scriptId >= scriptId;
        }
    };

    using UsedNameMap = HashMap<JSAtom*,
                                UsedNameInfo,
                                DefaultHasher<JSAtom*>>;

  private:
    // The map of names to chains of uses.
    UsedNameMap map_;

    // Monotonically increasing id for all nested scripts.
    uint32_t scriptCounter_;

    // Monotonically increasing id for all nested scopes.
    uint32_t scopeCounter_;

  public:
    explicit UsedNameTracker(JSContext* cx)
      : map_(cx),
        scriptCounter_(0),
        scopeCounter_(0)
    { }

    uint32_t nextScriptId() {
        MOZ_ASSERT(scriptCounter_ != UINT32_MAX,
                   "ParseContext::Scope::init should have prevented wraparound");
        return scriptCounter_++;
    }

    uint32_t nextScopeId() {
        MOZ_ASSERT(scopeCounter_ != UINT32_MAX);
        return scopeCounter_++;
    }

    UsedNameMap::Ptr lookup(JSAtom* name) const {
        return map_.lookup(name);
    }

    MOZ_MUST_USE bool noteUse(JSContext* cx, JSAtom* name,
                              uint32_t scriptId, uint32_t scopeId);

    struct RewindToken
    {
      private:
        friend class UsedNameTracker;
        uint32_t scriptId;
        uint32_t scopeId;
    };

    RewindToken getRewindToken() const {
        RewindToken token;
        token.scriptId = scriptCounter_;
        token.scopeId = scopeCounter_;
        return token;
    }

    // Resets state so that scriptId and scopeId are the innermost script and
    // scope, respectively. Used for rewinding state on syntax parse failure.
    void rewind(RewindToken token);

    // Resets state to beginning of compilation.
    void reset() {
        map_.clear();
        RewindToken token;
        token.scriptId = 0;
        token.scopeId = 0;
        rewind(token);
    }
};

/*
 * The struct ParseContext stores information about the current parsing context,
 * which is part of the parser state (see the field Parser::pc). The current
 * parsing context is either the global context, or the function currently being
 * parsed. When the parser encounters a function definition, it creates a new
 * ParseContext, makes it the new current context.
 */
class ParseContext : public Nestable<ParseContext>
{
  public:
    // The intra-function statement stack.
    //
    // Used for early error checking that depend on the nesting structure of
    // statements, such as continue/break targets, labels, and unbraced
    // lexical declarations.
    class Statement : public Nestable<Statement>
    {
        StatementKind kind_;

      public:
        using Nestable<Statement>::enclosing;
        using Nestable<Statement>::findNearest;

        Statement(ParseContext* pc, StatementKind kind)
          : Nestable<Statement>(&pc->innermostStatement_),
            kind_(kind)
        { }

        template <typename T> inline bool is() const;
        template <typename T> inline T& as();

        StatementKind kind() const {
            return kind_;
        }

        void refineForKind(StatementKind newForKind) {
            MOZ_ASSERT(kind_ == StatementKind::ForLoop);
            MOZ_ASSERT(newForKind == StatementKind::ForInLoop ||
                       newForKind == StatementKind::ForOfLoop);
            kind_ = newForKind;
        }
    };

    class LabelStatement : public Statement
    {
        RootedAtom label_;

      public:
        LabelStatement(ParseContext* pc, JSAtom* label)
          : Statement(pc, StatementKind::Label),
            label_(pc->sc_->context, label)
        { }

        HandleAtom label() const {
            return label_;
        }
    };

    struct ClassStatement : public Statement
    {
        FunctionBox* constructorBox;

        explicit ClassStatement(ParseContext* pc)
          : Statement(pc, StatementKind::Class),
            constructorBox(nullptr)
        { }
    };

    // The intra-function scope stack.
    //
    // Tracks declared and used names within a scope.
    class Scope : public Nestable<Scope>
    {
        // Names declared in this scope. Corresponds to the union of
        // VarDeclaredNames and LexicallyDeclaredNames in the ES spec.
        //
        // A 'var' declared name is a member of the declared name set of every
        // scope in its scope contour.
        //
        // A lexically declared name is a member only of the declared name set of
        // the scope in which it is declared.
        PooledMapPtr<DeclaredNameMap> declared_;

        // FunctionBoxes in this scope that need to be considered for Annex
        // B.3.3 semantics. This is checked on Scope exit, as by then we have
        // all the declared names and would know if Annex B.3.3 is applicable.
        PooledVectorPtr<FunctionBoxVector> possibleAnnexBFunctionBoxes_;

        // Monotonically increasing id.
        uint32_t id_;

        bool maybeReportOOM(ParseContext* pc, bool result) {
            if (!result)
                ReportOutOfMemory(pc->sc()->context);
            return result;
        }

      public:
        using DeclaredNamePtr = DeclaredNameMap::Ptr;
        using AddDeclaredNamePtr = DeclaredNameMap::AddPtr;

        using Nestable<Scope>::enclosing;

        explicit inline Scope(ParserBase* parser);
        explicit inline Scope(JSContext* cx, ParseContext* pc, UsedNameTracker& usedNames);

        void dump(ParseContext* pc);

        uint32_t id() const {
            return id_;
        }

        MOZ_MUST_USE bool init(ParseContext* pc) {
            if (id_ == UINT32_MAX) {
                pc->errorReporter_.reportErrorNoOffset(JSMSG_NEED_DIET, js_script_str);
                return false;
            }

            return declared_.acquire(pc->sc()->context);
        }

        bool isEmpty() const {
            return declared_->all().empty();
        }

        DeclaredNamePtr lookupDeclaredName(JSAtom* name) {
            return declared_->lookup(name);
        }

        AddDeclaredNamePtr lookupDeclaredNameForAdd(JSAtom* name) {
            return declared_->lookupForAdd(name);
        }

        MOZ_MUST_USE bool addDeclaredName(ParseContext* pc, AddDeclaredNamePtr& p, JSAtom* name,
                                          DeclarationKind kind, uint32_t pos)
        {
            return maybeReportOOM(pc, declared_->add(p, name, DeclaredNameInfo(kind, pos)));
        }

        // Add a FunctionBox as a possible candidate for Annex B.3.3 semantics.
        MOZ_MUST_USE bool addPossibleAnnexBFunctionBox(ParseContext* pc, FunctionBox* funbox);

        // Check if the candidate function boxes for Annex B.3.3 should in
        // fact get Annex B semantics. Checked on Scope exit.
        MOZ_MUST_USE bool propagateAndMarkAnnexBFunctionBoxes(ParseContext* pc);

        // Add and remove catch parameter names. Used to implement the odd
        // semantics of catch bodies.
        bool addCatchParameters(ParseContext* pc, Scope& catchParamScope);
        void removeCatchParameters(ParseContext* pc, Scope& catchParamScope);

        void useAsVarScope(ParseContext* pc) {
            MOZ_ASSERT(!pc->varScope_);
            pc->varScope_ = this;
        }

        // An iterator for the set of names a scope binds: the set of all
        // declared names for 'var' scopes, and the set of lexically declared
        // names for non-'var' scopes.
        class BindingIter
        {
            friend class Scope;

            DeclaredNameMap::Range declaredRange_;
            mozilla::DebugOnly<uint32_t> count_;
            bool isVarScope_;

            BindingIter(Scope& scope, bool isVarScope)
              : declaredRange_(scope.declared_->all()),
                count_(0),
                isVarScope_(isVarScope)
            {
                settle();
            }

            void settle() {
                // Both var and lexically declared names are binding in a var
                // scope.
                if (isVarScope_)
                    return;

                // Otherwise, pop only lexically declared names are
                // binding. Pop the range until we find such a name.
                while (!declaredRange_.empty()) {
                    if (BindingKindIsLexical(kind()))
                        break;
                    declaredRange_.popFront();
                }
            }

          public:
            bool done() const {
                return declaredRange_.empty();
            }

            explicit operator bool() const {
                return !done();
            }

            JSAtom* name() {
                MOZ_ASSERT(!done());
                return declaredRange_.front().key();
            }

            DeclarationKind declarationKind() {
                MOZ_ASSERT(!done());
                return declaredRange_.front().value()->kind();
            }

            BindingKind kind() {
                return DeclarationKindToBindingKind(declarationKind());
            }

            bool closedOver() {
                MOZ_ASSERT(!done());
                return declaredRange_.front().value()->closedOver();
            }

            void setClosedOver() {
                MOZ_ASSERT(!done());
                return declaredRange_.front().value()->setClosedOver();
            }

            void operator++(int) {
                MOZ_ASSERT(!done());
                MOZ_ASSERT(count_ != UINT32_MAX);
                declaredRange_.popFront();
                settle();
            }
        };

        inline BindingIter bindings(ParseContext* pc);
    };

    class VarScope : public Scope
    {
      public:
        explicit inline VarScope(ParserBase* parser);
        explicit inline VarScope(JSContext* cx, ParseContext* pc, UsedNameTracker& usedNames);
    };

  private:
    // Trace logging of parsing time.
    AutoFrontendTraceLog traceLog_;

    // Context shared between parsing and bytecode generation.
    SharedContext* sc_;

    // A mechanism used for error reporting.
    ErrorReporter& errorReporter_;

    // The innermost statement, i.e., top of the statement stack.
    Statement* innermostStatement_;

    // The innermost scope, i.e., top of the scope stack.
    //
    // The outermost scope in the stack is usually varScope_. In the case of
    // functions, the outermost scope is functionScope_, which may be
    // varScope_. See comment above functionScope_.
    Scope* innermostScope_;

    // If isFunctionBox() and the function is a named lambda, the DeclEnv
    // scope for named lambdas.
    mozilla::Maybe<Scope> namedLambdaScope_;

    // If isFunctionBox(), the scope for the function. If there are no
    // parameter expressions, this is scope for the entire function. If there
    // are parameter expressions, this holds the special function names
    // ('.this', 'arguments') and the formal parameters.
    mozilla::Maybe<Scope> functionScope_;

    // The body-level scope. This always exists, but not necessarily at the
    // beginning of parsing the script in the case of functions with parameter
    // expressions.
    Scope* varScope_;

    // Simple formal parameter names, in order of appearance. Only used when
    // isFunctionBox().
    PooledVectorPtr<AtomVector> positionalFormalParameterNames_;

    // Closed over binding names, in order of appearance. Null-delimited
    // between scopes. Only used when syntax parsing.
    PooledVectorPtr<AtomVector> closedOverBindingsForLazy_;

  public:
    // All inner functions in this context. Only used when syntax parsing.
    Rooted<GCVector<JSFunction*, 8>> innerFunctionsForLazy;

    // In a function context, points to a Directive struct that can be updated
    // to reflect new directives encountered in the Directive Prologue that
    // require reparsing the function. In global/module/generator-tail contexts,
    // we don't need to reparse when encountering a DirectivePrologue so this
    // pointer may be nullptr.
    Directives* newDirectives;

    // lastYieldOffset stores the offset of the last yield that was parsed.
    // NoYieldOffset is its initial value.
    static const uint32_t NoYieldOffset = UINT32_MAX;
    uint32_t lastYieldOffset;

    // lastAwaitOffset stores the offset of the last await that was parsed.
    // NoAwaitOffset is its initial value.
    static const uint32_t NoAwaitOffset = UINT32_MAX;
    uint32_t lastAwaitOffset;

  private:
    // Monotonically increasing id.
    uint32_t scriptId_;

    // Set when compiling a function using Parser::standaloneFunctionBody via
    // the Function or Generator constructor.
    bool isStandaloneFunctionBody_;

    // Set when encountering a super.property inside a method. We need to mark
    // the nearest super scope as needing a home object.
    bool superScopeNeedsHomeObject_;

  public:
    ParseContext(JSContext* cx, ParseContext*& parent, SharedContext* sc,
                 ErrorReporter& errorReporter, UsedNameTracker& usedNames,
                 Directives* newDirectives, bool isFull);

    MOZ_MUST_USE bool init();

    SharedContext* sc() {
        return sc_;
    }

    // `true` if we are in the body of a function definition.
    bool isFunctionBox() const {
        return sc_->isFunctionBox();
    }

    FunctionBox* functionBox() {
        return sc_->asFunctionBox();
    }

    Statement* innermostStatement() {
        return innermostStatement_;
    }

    Scope* innermostScope() {
        // There is always at least one scope: the 'var' scope.
        MOZ_ASSERT(innermostScope_);
        return innermostScope_;
    }

    Scope& namedLambdaScope() {
        MOZ_ASSERT(functionBox()->function()->isNamedLambda());
        return *namedLambdaScope_;
    }

    Scope& functionScope() {
        MOZ_ASSERT(isFunctionBox());
        return *functionScope_;
    }

    Scope& varScope() {
        MOZ_ASSERT(varScope_);
        return *varScope_;
    }

    bool isFunctionExtraBodyVarScopeInnermost() {
        return isFunctionBox() && functionBox()->hasParameterExprs &&
               innermostScope() == varScope_;
    }

    template <typename Predicate /* (Statement*) -> bool */>
    Statement* findInnermostStatement(Predicate predicate) {
        return Statement::findNearest(innermostStatement_, predicate);
    }

    template <typename T, typename Predicate /* (Statement*) -> bool */>
    T* findInnermostStatement(Predicate predicate) {
        return Statement::findNearest<T>(innermostStatement_, predicate);
    }

    template <typename T>
    T* findInnermostStatement() {
        return Statement::findNearest<T>(innermostStatement_);
    }

    AtomVector& positionalFormalParameterNames() {
        return *positionalFormalParameterNames_;
    }

    AtomVector& closedOverBindingsForLazy() {
        return *closedOverBindingsForLazy_;
    }

    enum class BreakStatementError {
        // Unlabeled break must be inside loop or switch.
        ToughBreak,
        LabelNotFound,
    };

    // Return Err(true) if we have encountered at least one loop,
    // Err(false) otherwise.
    MOZ_MUST_USE inline JS::Result<Ok, BreakStatementError> checkBreakStatement(PropertyName* label);

    enum class ContinueStatementError {
        NotInALoop,
        LabelNotFound,
    };
    MOZ_MUST_USE inline JS::Result<Ok, ContinueStatementError> checkContinueStatement(PropertyName* label);

    // True if we are at the topmost level of a entire script or function body.
    // For example, while parsing this code we would encounter f1 and f2 at
    // body level, but we would not encounter f3 or f4 at body level:
    //
    //   function f1() { function f2() { } }
    //   if (cond) { function f3() { if (cond) { function f4() { } } } }
    //
    bool atBodyLevel() {
        return !innermostStatement_;
    }

    bool atGlobalLevel() {
        return atBodyLevel() && sc_->isGlobalContext();
    }

    // True if we are at the topmost level of a module only.
    bool atModuleLevel() {
        return atBodyLevel() && sc_->isModuleContext();
    }

    void setIsStandaloneFunctionBody() {
        isStandaloneFunctionBody_ = true;
    }

    bool isStandaloneFunctionBody() const {
        return isStandaloneFunctionBody_;
    }

    void setSuperScopeNeedsHomeObject() {
        MOZ_ASSERT(sc_->allowSuperProperty());
        superScopeNeedsHomeObject_ = true;
    }

    bool superScopeNeedsHomeObject() const {
        return superScopeNeedsHomeObject_;
    }

    bool useAsmOrInsideUseAsm() const {
        return sc_->isFunctionBox() && sc_->asFunctionBox()->useAsmOrInsideUseAsm();
    }

    // A generator is marked as a generator before its body is parsed.
    GeneratorKind generatorKind() const {
        return sc_->isFunctionBox()
               ? sc_->asFunctionBox()->generatorKind()
               : GeneratorKind::NotGenerator;
    }

    bool isGenerator() const {
        return generatorKind() == GeneratorKind::Generator;
    }

    bool isAsync() const {
        return sc_->isFunctionBox() && sc_->asFunctionBox()->isAsync();
    }

    bool needsDotGeneratorName() const {
        return isGenerator() || isAsync();
    }

    FunctionAsyncKind asyncKind() const {
        return isAsync() ? FunctionAsyncKind::AsyncFunction : FunctionAsyncKind::SyncFunction;
    }

    bool isArrowFunction() const {
        return sc_->isFunctionBox() && sc_->asFunctionBox()->function()->isArrow();
    }

    bool isMethod() const {
        return sc_->isFunctionBox() && sc_->asFunctionBox()->function()->isMethod();
    }

    bool isGetterOrSetter() const {
        return sc_->isFunctionBox() && (sc_->asFunctionBox()->function()->isGetter() ||
                                        sc_->asFunctionBox()->function()->isSetter());
    }

    uint32_t scriptId() const {
        return scriptId_;
    }

    bool annexBAppliesToLexicalFunctionInInnermostScope(FunctionBox* funbox);

    bool tryDeclareVar(HandlePropertyName name, DeclarationKind kind, uint32_t beginPos,
                       mozilla::Maybe<DeclarationKind>* redeclaredKind, uint32_t* prevPos);

  private:
    mozilla::Maybe<DeclarationKind> isVarRedeclaredInInnermostScope(HandlePropertyName name,
                                                                    DeclarationKind kind);
    mozilla::Maybe<DeclarationKind> isVarRedeclaredInEval(HandlePropertyName name,
                                                          DeclarationKind kind);

    enum DryRunOption { NotDryRun, DryRunInnermostScopeOnly };
    template <DryRunOption dryRunOption>
    bool tryDeclareVarHelper(HandlePropertyName name, DeclarationKind kind, uint32_t beginPos,
                             mozilla::Maybe<DeclarationKind>* redeclaredKind, uint32_t* prevPos);

};

} // namespace frontend

} // namespace js

#endif // frontend_ParseContext_h