source: src/ResolvExpr/Resolver.cpp@ 0497b6ba

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Resolver.cpp --
//
// Author           : Aaron B. Moss
// Created On       : Sun May 17 12:17:01 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Thu Dec 14 18:44:43 2023
// Update Count     : 251
//

#include <cassert>                       // for strict_dynamic_cast, assert
#include <memory>                        // for allocator, allocator_traits<...
#include <tuple>                         // for get
#include <vector>                        // for vector

#include "Candidate.hpp"
#include "CandidateFinder.hpp"
#include "CurrentObject.hpp"             // for CurrentObject
#include "RenameVars.hpp"                // for RenameVars, global_renamer
#include "Resolver.hpp"
#include "ResolveTypeof.hpp"
#include "ResolveMode.hpp"               // for ResolveMode
#include "Typeops.hpp"                   // for extractResultType
#include "Unify.hpp"                     // for unify
#include "CompilationState.hpp"
#include "AST/Decl.hpp"
#include "AST/Init.hpp"
#include "AST/Pass.hpp"
#include "AST/Print.hpp"
#include "AST/SymbolTable.hpp"
#include "AST/Type.hpp"
#include "Common/Eval.hpp"               // for eval
#include "Common/Iterate.hpp"            // for group_iterate
#include "Common/SemanticError.hpp"      // for SemanticError
#include "Common/Stats/ResolveTime.hpp"  // for ResolveTime::start(), ResolveTime::stop()
#include "Common/ToString.hpp"           // for toCString
#include "Common/UniqueName.hpp"         // for UniqueName
#include "InitTweak/GenInit.hpp"
#include "InitTweak/InitTweak.hpp"       // for isIntrinsicSingleArgCallStmt
#include "SymTab/Mangler.hpp"            // for Mangler
#include "Tuples/Tuples.hpp"
#include "Validate/FindSpecialDecls.hpp" // for SizeType

using namespace std;

namespace ResolvExpr {

namespace {
        /// Finds deleted expressions in an expression tree
        struct DeleteFinder final : public ast::WithShortCircuiting, public ast::WithVisitorRef<DeleteFinder> {
                const ast::DeletedExpr * result = nullptr;

                void previsit( const ast::DeletedExpr * expr ) {
                        if ( result ) { visit_children = false; }
                        else { result = expr; }
                }

                void previsit( const ast::Expr * expr ) {
                        if ( result ) { visit_children = false; }
                        if (expr->inferred.hasParams()) {
                                for (auto & imp : expr->inferred.inferParams() ) {
                                        imp.second.expr->accept(*visitor);
                                }
                        }
                }
        };

        struct ResolveDesignators final : public ast::WithShortCircuiting {
                ResolveContext& context;
                bool result = false;

                ResolveDesignators( ResolveContext& _context ): context(_context) {};

                void previsit( const ast::Node * ) {
                        // short circuit if we already know there are designations
                        if ( result ) visit_children = false;
                }

                void previsit( const ast::Designation * des ) {
                        if ( result ) visit_children = false;
                        else if ( ! des->designators.empty() ) {
                                if ( (des->designators.size() == 1) ) {
                                        const ast::Expr * designator = des->designators.at(0);
                                        if ( const ast::NameExpr * designatorName = dynamic_cast<const ast::NameExpr *>(designator) ) {
                                                auto candidates = context.symtab.lookupId(designatorName->name);
                                                for ( auto candidate : candidates ) {
                                                        if ( dynamic_cast<const ast::EnumInstType *>(candidate.id->get_type()) ) {
                                                                result = true;
                                                                break;
                                                        }
                                                }
                                        }
                                }
                                visit_children = false;
                        }
                }
        };
} // anonymous namespace

/// Check if this expression is or includes a deleted expression
const ast::DeletedExpr * findDeletedExpr( const ast::Expr * expr ) {
        return ast::Pass<DeleteFinder>::read( expr );
}

namespace {
        /// always-accept candidate filter
        bool anyCandidate( const Candidate & ) { return true; }

        /// Calls the CandidateFinder and finds the single best candidate
        CandidateRef findUnfinishedKindExpression(
                const ast::Expr * untyped, const ResolveContext & context, const std::string & kind,
                std::function<bool(const Candidate &)> pred = anyCandidate, ResolveMode mode = {}
        ) {
                if ( ! untyped ) return nullptr;

                // xxx - this isn't thread-safe, but should work until we parallelize the resolver
                static unsigned recursion_level = 0;

                ++recursion_level;
                ast::TypeEnvironment env;
                CandidateFinder finder( context, env );
                finder.allowVoid = true;
                finder.find( untyped, recursion_level == 1 ? mode.atTopLevel() : mode );
                --recursion_level;

                // produce a filtered list of candidates
                CandidateList candidates;
                for ( auto & cand : finder.candidates ) {
                        if ( pred( *cand ) ) { candidates.emplace_back( cand ); }
                }

                // produce invalid error if no candidates
                if ( candidates.empty() ) {
                        SemanticError( untyped,
                                toString( "No reasonable alternatives for ", kind, (kind != "" ? " " : ""),
                                "expression: ") );
                }

                // search for cheapest candidate
                CandidateList winners;
                bool seen_undeleted = false;
                for ( CandidateRef & cand : candidates ) {
                        int c = winners.empty() ? -1 : cand->cost.compare( winners.front()->cost );

                        if ( c > 0 ) continue;  // skip more expensive than winner

                        if ( c < 0 ) {
                                // reset on new cheapest
                                seen_undeleted = ! findDeletedExpr( cand->expr );
                                winners.clear();
                        } else /* if ( c == 0 ) */ {
                                if ( findDeletedExpr( cand->expr ) ) {
                                        // skip deleted expression if already seen one equivalent-cost not
                                        if ( seen_undeleted ) continue;
                                } else if ( ! seen_undeleted ) {
                                        // replace list of equivalent-cost deleted expressions with one non-deleted
                                        winners.clear();
                                        seen_undeleted = true;
                                }
                        }

                        winners.emplace_back( std::move( cand ) );
                }

                // promote candidate.cvtCost to .cost
                // promoteCvtCost( winners );

                // produce ambiguous errors, if applicable
                if ( winners.size() != 1 ) {
                        std::ostringstream stream;
                        stream << "Cannot choose between " << winners.size() << " alternatives for "
                                << kind << (kind != "" ? " " : "") << "expression\n";
                        ast::print( stream, untyped );
                        stream << " Alternatives are:\n";
                        print( stream, winners, 1 );
                        SemanticError( untyped->location, stream.str() );
                }

                // single selected choice
                CandidateRef & choice = winners.front();

                // fail on only expression deleted
                if ( ! seen_undeleted ) {
                        SemanticError( untyped->location, choice->expr.get(), "Unique best alternative "
                        "includes deleted identifier in " );
                }

                return std::move( choice );
        }

        /// Strips extraneous casts out of an expression
        struct StripCasts final {
                const ast::Expr * postvisit( const ast::CastExpr * castExpr ) {
                        if (
                                castExpr->isGenerated == ast::GeneratedCast
                                && typesCompatible( castExpr->arg->result, castExpr->result )
                        ) {
                                ast::EnumInstType const * arg, * result;
                                if ( ( result = castExpr->result.as<ast::EnumInstType>() ) &&
                                                ( arg = castExpr->arg.as<ast::EnumInstType>() ) &&
                                                arg->base->name != result->base->name) {
                                        return castExpr;
                                }
                                // generated cast is the same type as its argument, remove it after keeping env
                                return ast::mutate_field(
                                        castExpr->arg.get(), &ast::Expr::env, castExpr->env );
                        }
                        return castExpr;
                }

                static void strip( ast::ptr< ast::Expr > & expr ) {
                        ast::Pass< StripCasts > stripper;
                        expr = expr->accept( stripper );
                }
        };

        /// Swaps argument into expression pointer, saving original environment
        void swap_and_save_env( ast::ptr< ast::Expr > & expr, const ast::Expr * newExpr ) {
                ast::ptr< ast::TypeSubstitution > env = expr->env;
                expr.set_and_mutate( newExpr )->env = env;
        }

        /// Removes cast to type of argument (unlike StripCasts, also handles non-generated casts)
        void removeExtraneousCast( ast::ptr<ast::Expr> & expr ) {
                if ( const ast::CastExpr * castExpr = expr.as< ast::CastExpr >() ) {
                        if ( typesCompatible( castExpr->arg->result, castExpr->result ) ) {
                                // cast is to the same type as its argument, remove it
                                swap_and_save_env( expr, castExpr->arg );
                        }
                }
        }

} // anonymous namespace

/// Establish post-resolver invariants for expressions
void finishExpr(
        ast::ptr< ast::Expr > & expr, const ast::TypeEnvironment & env,
        const ast::TypeSubstitution * oldenv = nullptr
) {
        // set up new type substitution for expression
        ast::ptr< ast::TypeSubstitution > newenv =
                 oldenv ? oldenv : new ast::TypeSubstitution{};
        env.writeToSubstitution( *newenv.get_and_mutate() );
        expr.get_and_mutate()->env = std::move( newenv );
        // remove unncecessary casts
        StripCasts::strip( expr );
}

ast::ptr< ast::Expr > resolveInVoidContext(
        const ast::Expr * expr, const ResolveContext & context,
        ast::TypeEnvironment & env
) {
        assertf( expr, "expected a non-null expression" );

        // set up and resolve expression cast to void
        ast::ptr< ast::CastExpr > untyped = new ast::CastExpr{ expr };
        CandidateRef choice = findUnfinishedKindExpression(
                untyped, context, "", anyCandidate );

        // a cast expression has either 0 or 1 interpretations (by language rules);
        // if 0, an exception has already been thrown, and this code will not run
        const ast::CastExpr * castExpr = choice->expr.strict_as< ast::CastExpr >();
        env = std::move( choice->env );

        return castExpr->arg;
}

/// Resolve `untyped` to the expression whose candidate is the best match for a `void`
/// context.
ast::ptr< ast::Expr > findVoidExpression(
        const ast::Expr * untyped, const ResolveContext & context
) {
        ast::TypeEnvironment env;
        ast::ptr< ast::Expr > newExpr = resolveInVoidContext( untyped, context, env );
        finishExpr( newExpr, env, untyped->env );
        return newExpr;
}

namespace {
        /// resolve `untyped` to the expression whose candidate satisfies `pred` with the
        /// lowest cost, returning the resolved version
        ast::ptr< ast::Expr > findKindExpression(
                const ast::Expr * untyped, const ResolveContext & context,
                std::function<bool(const Candidate &)> pred = anyCandidate,
                const std::string & kind = "", ResolveMode mode = {}
        ) {
                if ( ! untyped ) return {};
                CandidateRef choice =
                        findUnfinishedKindExpression( untyped, context, kind, pred, mode );
                ResolvExpr::finishExpr( choice->expr, choice->env, untyped->env );
                return std::move( choice->expr );
        }

        /// Resolve `untyped` to the single expression whose candidate is the best match
        ast::ptr< ast::Expr > findSingleExpression(
                const ast::Expr * untyped, const ResolveContext & context
        ) {
                Stats::ResolveTime::start( untyped );
                auto res = findKindExpression( untyped, context );
                Stats::ResolveTime::stop();
                return res;
        }
} // anonymous namespace

ast::ptr< ast::Expr > findSingleExpression(
        const ast::Expr * untyped, const ast::Type * type,
        const ResolveContext & context
) {
        assert( untyped && type );
        ast::ptr< ast::Expr > castExpr = new ast::CastExpr{ untyped, type };
        ast::ptr< ast::Expr > newExpr = findSingleExpression( castExpr, context );
        removeExtraneousCast( newExpr );
        return newExpr;
}

namespace {
        bool structOrUnionOrEnum( const Candidate & i ) {
                const ast::Type * t = i.expr->result->stripReferences();
                return dynamic_cast< const ast::StructInstType * >( t ) || dynamic_cast< const ast::UnionInstType * >( t ) || dynamic_cast< const ast::EnumInstType * >( t );
        }
        /// Predicate for "Candidate has integral type"
        bool hasIntegralType( const Candidate & i ) {
                const ast::Type * type = i.expr->result;

                if ( auto bt = dynamic_cast< const ast::BasicType * >( type ) ) {
                        return bt->isInteger();
                } else if (
                        dynamic_cast< const ast::EnumInstType * >( type )
                        || dynamic_cast< const ast::ZeroType * >( type )
                        || dynamic_cast< const ast::OneType * >( type )
                ) {
                        return true;
                } else return false;
        }

        /// Resolve `untyped` as an integral expression, returning the resolved version
        ast::ptr< ast::Expr > findIntegralExpression(
                const ast::Expr * untyped, const ResolveContext & context
        ) {
                return findKindExpression( untyped, context, hasIntegralType, "condition" );
        }

        ast::ptr< ast::Expr > findCondExpression(
                const ast::Expr * untyped, const ResolveContext & context
        ) {
                if ( nullptr == untyped ) return untyped;
                ast::ptr<ast::Expr> condExpr = createCondExpr( untyped );
                return findIntegralExpression( condExpr, context );
        }

        /// check if a type is a character type
        bool isCharType( const ast::Type * t ) {
                if ( auto bt = dynamic_cast< const ast::BasicType * >( t ) ) {
                        return bt->kind == ast::BasicKind::Char
                                || bt->kind == ast::BasicKind::SignedChar
                                || bt->kind == ast::BasicKind::UnsignedChar;
                }
                return false;
        }

        /// Advance a type itertor to the next mutex parameter
        template<typename Iter>
        inline bool nextMutex( Iter & it, const Iter & end ) {
                while ( it != end && ! (*it)->is_mutex() ) { ++it; }
                return it != end;
        }
} // anonymous namespace

class Resolver final
: public ast::WithSymbolTable, public ast::WithGuards,
  public ast::WithVisitorRef<Resolver>, public ast::WithShortCircuiting,
  public ast::WithStmtsToAdd {

        ast::ptr< ast::Type > functionReturn = nullptr;
        ast::CurrentObject currentObject;
        // for work previously in GenInit
        static InitTweak::ManagedTypes managedTypes;
        ResolveContext context;

        bool inEnumDecl = false;

public:
        static size_t traceId;
        Resolver( const ast::TranslationGlobal & global ) :
                ast::WithSymbolTable(ast::SymbolTable::ErrorDetection::ValidateOnAdd),
                context{ symtab, global } {}
        Resolver( const ResolveContext & context ) :
                ast::WithSymbolTable{ context.symtab },
                context{ symtab, context.global } {}

        const ast::FunctionDecl * previsit( const ast::FunctionDecl * );
        const ast::FunctionDecl * postvisit( const ast::FunctionDecl * );
        const ast::ObjectDecl * previsit( const ast::ObjectDecl * );
        void previsit( const ast::AggregateDecl * );
        void previsit( const ast::StructDecl * );
        void previsit( const ast::EnumDecl * );
        const ast::StaticAssertDecl * previsit( const ast::StaticAssertDecl * );

        const ast::ArrayType * previsit( const ast::ArrayType * );
        const ast::PointerType * previsit( const ast::PointerType * );

        const ast::ExprStmt *        previsit( const ast::ExprStmt * );
        const ast::AsmExpr *         previsit( const ast::AsmExpr * );
        const ast::AsmStmt *         previsit( const ast::AsmStmt * );
        const ast::IfStmt *          previsit( const ast::IfStmt * );
        const ast::WhileDoStmt *     previsit( const ast::WhileDoStmt * );
        const ast::ForStmt *         previsit( const ast::ForStmt * );
        const ast::SwitchStmt *      previsit( const ast::SwitchStmt * );
        const ast::CaseClause *      previsit( const ast::CaseClause * );
        const ast::BranchStmt *      previsit( const ast::BranchStmt * );
        const ast::ReturnStmt *      previsit( const ast::ReturnStmt * );
        const ast::ThrowStmt *       previsit( const ast::ThrowStmt * );
        const ast::CatchClause *     previsit( const ast::CatchClause * );
        const ast::CatchClause *     postvisit( const ast::CatchClause * );
        const ast::WaitForStmt *     previsit( const ast::WaitForStmt * );
        const ast::WithStmt *        previsit( const ast::WithStmt * );

        const ast::SingleInit *      previsit( const ast::SingleInit * );
        const ast::ListInit *        previsit( const ast::ListInit * );
        const ast::ConstructorInit * previsit( const ast::ConstructorInit * );

        void resolveWithExprs(std::vector<ast::ptr<ast::Expr>> & exprs, std::list<ast::ptr<ast::Stmt>> & stmtsToAdd);
        bool shouldGenCtorInit( const ast::ObjectDecl * ) const;

        void beginScope() { managedTypes.beginScope(); }
        void endScope() { managedTypes.endScope(); }
        bool on_error(ast::ptr<ast::Decl> & decl);
};
// size_t Resolver::traceId = Stats::Heap::new_stacktrace_id("Resolver");

InitTweak::ManagedTypes Resolver::managedTypes;

void resolve( ast::TranslationUnit& translationUnit ) {
        ast::Pass< Resolver >::run( translationUnit, translationUnit.global );
}

ast::ptr< ast::Init > resolveCtorInit(
        const ast::ConstructorInit * ctorInit, const ResolveContext & context
) {
        assert( ctorInit );
        ast::Pass< Resolver > resolver( context );
        return ctorInit->accept( resolver );
}

const ast::Expr * resolveStmtExpr(
        const ast::StmtExpr * stmtExpr, const ResolveContext & context
) {
        assert( stmtExpr );
        ast::Pass< Resolver > resolver( context );
        auto ret = mutate(stmtExpr->accept(resolver));
        strict_dynamic_cast< ast::StmtExpr * >( ret )->computeResult();
        return ret;
}

namespace {
        const ast::Attribute * handleAttribute(const CodeLocation & loc, const ast::Attribute * attr, const ResolveContext & context) {
                std::string name = attr->normalizedName();
                if (name == "constructor" || name == "destructor") {
                        if (attr->params.size() == 1) {
                                auto arg = attr->params.front();
                                auto resolved = ResolvExpr::findSingleExpression( arg, new ast::BasicType( ast::BasicKind::LongLongSignedInt ), context );
                                auto result = eval(arg);

                                auto mutAttr = mutate(attr);
                                mutAttr->params.front() = resolved;
                                if (! result.hasKnownValue) {
                                        SemanticWarning(loc, Warning::GccAttributes,
                                                toCString( name, " priorities must be integers from 0 to 65535 inclusive: ", arg ) );
                                }
                                else {
                                        auto priority = result.knownValue;
                                        if (priority < 101) {
                                                SemanticWarning(loc, Warning::GccAttributes,
                                                        toCString( name, " priorities from 0 to 100 are reserved for the implementation" ) );
                                        } else if (priority < 201 && ! buildingLibrary()) {
                                                SemanticWarning(loc, Warning::GccAttributes,
                                                        toCString( name, " priorities from 101 to 200 are reserved for the implementation" ) );
                                        }
                                }
                                return mutAttr;
                        } else if (attr->params.size() > 1) {
                                SemanticWarning(loc, Warning::GccAttributes, toCString( "too many arguments to ", name, " attribute" ) );
                        } else {
                                SemanticWarning(loc, Warning::GccAttributes, toCString( "too few arguments to ", name, " attribute" ) );
                        }
                }
                return attr;
        }
}

// Returns a version of `ty`, with some detail redacted.
// `ty` is that of a parameter or return of `functionDecl`.
// Redaction:
//   - concerns the dimension expression, when `ty` is a pointer or array
//   - prevents escape of variables bound by other parameter declarations
//   - replaces the whole dimension with `*` if it uses such a variable
//   - produces the caller's view of `functionDecl`, where `ty` is from the callee/body's view
// Example 1
//   functionDecl:     void   f( int n, float a[][5][n + 1] );
//   outcome:      f : void (*)( int  , float  [][5][*]     ), redaction on deepest ArrayType
// Example 2
//   functionDecl:     void   f( int n, float a[n] );
//   outcome:      f : void (*)( int  , float  [*]     ), redaction on PointerType
// Example 3
//   in scope:         int n;
//   functionDecl:     void   f( float a[][n] );
//   outcome:      f : void (*)( float  [][n] ), no redaction
static const ast::Type * redactBoundDimExprs(
        const ast::Type * ty,
        const ast::FunctionDecl * functionDecl
);
struct UsesParams {
        const ast::FunctionDecl * functionDecl;
        UsesParams( const ast::FunctionDecl * functionDecl ) : functionDecl(functionDecl) {}
        bool result = false;
        void postvisit( const ast::VariableExpr * e ) {
                for ( auto p : functionDecl->params ) {
                        if ( p.get() == e->var ) result = true;
                }
        }
};
struct Redactor {
        const ast::FunctionDecl * functionDecl;
        Redactor( const ast::FunctionDecl * functionDecl ) : functionDecl(functionDecl) {}
        template< typename PtrType >
        const PtrType * postvisitImpl( const PtrType * type ) {
                if ( type->dimension && ast::Pass<UsesParams>::read( type->dimension.get(), functionDecl ) ) {
                        // PtrType * newtype = ast::shallowCopy( type );
                        // newtype->dimension = nullptr;
                        // type = newtype;
                        auto mutType = mutate(type);
                        mutType->dimension = nullptr;
                        type = mutType;
                }
                return type;
        }

        const ast::ArrayType * postvisit (const ast::ArrayType * arrayType) {
                return postvisitImpl( arrayType );
        }

        const ast::PointerType * postvisit (const ast::PointerType * pointerType) {
                return postvisitImpl( pointerType );
        }
};
static const ast::Type * redactBoundDimExprs(
        const ast::Type * ty,
        const ast::FunctionDecl * functionDecl
) {
        if ( ast::Pass<UsesParams>::read( ty, functionDecl ) ) {
                ast::Type * newty = ast::deepCopy( ty );
                ast::Pass<Redactor> visitor(functionDecl);
                ty = newty->accept(visitor);
        }
        return ty;
}

const ast::FunctionDecl * Resolver::previsit( const ast::FunctionDecl * functionDecl ) {
        GuardValue( functionReturn );

        assert (functionDecl->unique());
        if (!functionDecl->has_body() && !functionDecl->withExprs.empty()) {
                SemanticError(functionDecl->location, functionDecl, "Function without body has with declarations");
        }

        if (!functionDecl->isTypeFixed) {
                auto mutDecl = mutate(functionDecl);
                auto mutType = mutDecl->type.get_and_mutate();

                for (auto & attr: mutDecl->attributes) {
                        attr = handleAttribute(mutDecl->location, attr, context );
                }

                // handle assertions

                symtab.enterScope();
                mutType->forall.clear();
                mutType->assertions.clear();
                for (auto & typeParam : mutDecl->type_params) {
                        symtab.addType(typeParam);
                        mutType->forall.emplace_back(new ast::TypeInstType(typeParam));
                }
                for (auto & asst : mutDecl->assertions) {
                        asst = fixObjectType(asst.strict_as<ast::ObjectDecl>(), context);
                        symtab.addId(asst);
                        mutType->assertions.emplace_back(new ast::VariableExpr(functionDecl->location, asst));
                }

                // temporarily adds params to symbol table.
                // actual scoping rules for params and withexprs differ - see Pass::visit(FunctionDecl)

                std::vector<ast::ptr<ast::Type>> paramTypes;
                std::vector<ast::ptr<ast::Type>> returnTypes;

                for (auto & param : mutDecl->params) {
                        param = fixObjectType(param.strict_as<ast::ObjectDecl>(), context);
                        symtab.addId(param);
                        auto exportParamT = redactBoundDimExprs( param->get_type(), mutDecl );
                        paramTypes.emplace_back( exportParamT );
                }
                for (auto & ret : mutDecl->returns) {
                        ret = fixObjectType(ret.strict_as<ast::ObjectDecl>(), context);
                        auto exportRetT = redactBoundDimExprs( ret->get_type(), mutDecl );
                        returnTypes.emplace_back( exportRetT );
                }
                // since function type in decl is just a view of param types, need to update that as well
                mutType->params = std::move(paramTypes);
                mutType->returns = std::move(returnTypes);

                auto renamedType = strict_dynamic_cast<const ast::FunctionType *>(renameTyVars(mutType, RenameMode::GEN_EXPR_ID));

                std::list<ast::ptr<ast::Stmt>> newStmts;
                resolveWithExprs (mutDecl->withExprs, newStmts);

                if (mutDecl->stmts) {
                        auto mutStmt = mutDecl->stmts.get_and_mutate();
                        mutStmt->kids.splice(mutStmt->kids.begin(), std::move(newStmts));
                        mutDecl->stmts = mutStmt;
                }

                symtab.leaveScope();

                mutDecl->type = renamedType;
                mutDecl->mangleName = Mangle::mangle(mutDecl);
                mutDecl->isTypeFixed = true;
                functionDecl = mutDecl;
        }
        managedTypes.handleDWT(functionDecl);

        functionReturn = extractResultType( functionDecl->type );
        return functionDecl;
}

const ast::FunctionDecl * Resolver::postvisit( const ast::FunctionDecl * functionDecl ) {
        // default value expressions have an environment which shouldn't be there and trips up
        // later passes.
        assert( functionDecl->unique() );
        ast::FunctionType * mutType = mutate( functionDecl->type.get() );

        for ( unsigned i = 0 ; i < mutType->params.size() ; ++i ) {
                if ( const ast::ObjectDecl * obj = mutType->params[i].as< ast::ObjectDecl >() ) {
                        if ( const ast::SingleInit * init = obj->init.as< ast::SingleInit >() ) {
                                if ( init->value->env == nullptr ) continue;
                                // clone initializer minus the initializer environment
                                auto mutParam = mutate( mutType->params[i].strict_as< ast::ObjectDecl >() );
                                auto mutInit = mutate( mutParam->init.strict_as< ast::SingleInit >() );
                                auto mutValue = mutate( mutInit->value.get() );

                                mutValue->env = nullptr;
                                mutInit->value = mutValue;
                                mutParam->init = mutInit;
                                mutType->params[i] = mutParam;

                                assert( ! mutType->params[i].strict_as< ast::ObjectDecl >()->init.strict_as< ast::SingleInit >()->value->env);
                        }
                }
        }
        mutate_field(functionDecl, &ast::FunctionDecl::type, mutType);
        return functionDecl;
}

bool Resolver::shouldGenCtorInit( ast::ObjectDecl const * decl ) const {
        // If we shouldn't try to construct it, then don't.
        if ( !InitTweak::tryConstruct( decl ) ) return false;
        // Otherwise, if it is a managed type, we may construct it.
        if ( managedTypes.isManaged( decl ) ) return true;
        // Skip construction if it is trivial at compile-time.
        if ( InitTweak::isConstExpr( decl->init ) ) return false;
        // Skip construction for local declarations.
        return ( !isInFunction() || decl->storage.is_static );
}

const ast::ObjectDecl * Resolver::previsit( const ast::ObjectDecl * objectDecl ) {
        // To handle initialization of routine pointers [e.g. int (*fp)(int) = foo()],
        // class-variable `initContext` is changed multiple times because the LHS is analyzed
        // twice. The second analysis changes `initContext` because a function type can contain
        // object declarations in the return and parameter types. Therefore each value of
        // `initContext` is retained so the type on the first analysis is preserved and used for
        // selecting the RHS.
        GuardValue( currentObject );

        if ( inEnumDecl && dynamic_cast< const ast::EnumInstType * >( objectDecl->get_type() ) ) {
                // enumerator initializers should not use the enum type to initialize, since the
                // enum type is still incomplete at this point. Use `int` instead.

                if ( auto enumBase = dynamic_cast< const ast::EnumInstType * >
                        ( objectDecl->get_type() )->base->base ) {
                        objectDecl = fixObjectType( objectDecl, context );
                        currentObject = ast::CurrentObject{
                                objectDecl->location,
                                enumBase
                        };
                } else {
                        objectDecl = fixObjectType( objectDecl, context );
                        currentObject = ast::CurrentObject{
                                objectDecl->location, new ast::BasicType{ ast::BasicKind::SignedInt } };
                }
        } else {
                if ( !objectDecl->isTypeFixed ) {
                        auto newDecl = fixObjectType(objectDecl, context);
                        auto mutDecl = mutate(newDecl);

                        // generate CtorInit wrapper when necessary.
                        // in certain cases, fixObjectType is called before reaching
                        // this object in visitor pass, thus disabling CtorInit codegen.
                        // this happens on aggregate members and function parameters.
                        if ( shouldGenCtorInit( mutDecl ) ) {
                                // constructed objects cannot be designated
                                if ( InitTweak::isDesignated( mutDecl->init ) ) {
                                        ast::Pass<ResolveDesignators> res( context );
                                        maybe_accept( mutDecl->init.get(), res );
                                        if ( !res.core.result ) {
                                                SemanticError( mutDecl, "Cannot include designations in the initializer for a managed Object.\n"
                                                                           "If this is really what you want, initialize with @=." );
                                        }
                                }
                                // constructed objects should not have initializers nested too deeply
                                if ( ! InitTweak::checkInitDepth( mutDecl ) ) SemanticError( mutDecl, "Managed object's initializer is too deep " );

                                mutDecl->init = InitTweak::genCtorInit( mutDecl->location, mutDecl );
                        }

                        objectDecl = mutDecl;
                }
                currentObject = ast::CurrentObject{ objectDecl->location, objectDecl->get_type() };
        }

        return objectDecl;
}

void Resolver::previsit( const ast::AggregateDecl * _aggDecl ) {
        auto aggDecl = mutate(_aggDecl);
        assertf(aggDecl == _aggDecl, "type declarations must be unique");

        for (auto & member: aggDecl->members) {
                // nested type decls are hoisted already. no need to do anything
                if (auto obj = member.as<ast::ObjectDecl>()) {
                        member = fixObjectType(obj, context);
                }
        }
}

void Resolver::previsit( const ast::StructDecl * structDecl ) {
        previsit(static_cast<const ast::AggregateDecl *>(structDecl));
        managedTypes.handleStruct(structDecl);
}

void Resolver::previsit( const ast::EnumDecl * ) {
        // in case we decide to allow nested enums
        GuardValue( inEnumDecl );
        inEnumDecl = true;
        // don't need to fix types for enum fields
}

const ast::StaticAssertDecl * Resolver::previsit(
        const ast::StaticAssertDecl * assertDecl
) {
        return ast::mutate_field(
                assertDecl, &ast::StaticAssertDecl::cond,
                findIntegralExpression( assertDecl->cond, context ) );
}

template< typename PtrType >
const PtrType * handlePtrType( const PtrType * type, const ResolveContext & context ) {
        // Note: resolving dimension expressions seems to require duplicate logic,
        // here and ResolveTypeof.cpp:fixArrayType.
        if ( type->dimension ) {
                const ast::Type * sizeType = context.global.sizeType.get();
                ast::ptr< ast::Expr > dimension = findSingleExpression( type->dimension, sizeType, context );
                assertf(dimension->env->empty(), "array dimension expr has nonempty env");
                dimension.get_and_mutate()->env = nullptr;
                type = ast::mutate_field( type, &PtrType::dimension, dimension );
        }
        return type;
}

const ast::ArrayType * Resolver::previsit( const ast::ArrayType * at ) {
        return handlePtrType( at, context );
}

const ast::PointerType * Resolver::previsit( const ast::PointerType * pt ) {
        return handlePtrType( pt, context );
}

const ast::ExprStmt * Resolver::previsit( const ast::ExprStmt * exprStmt ) {
        visit_children = false;
        assertf( exprStmt->expr, "ExprStmt has null expression in resolver" );

        return ast::mutate_field(
                exprStmt, &ast::ExprStmt::expr, findVoidExpression( exprStmt->expr, context ) );
}

const ast::AsmExpr * Resolver::previsit( const ast::AsmExpr * asmExpr ) {
        visit_children = false;

        asmExpr = ast::mutate_field(
                asmExpr, &ast::AsmExpr::operand, findVoidExpression( asmExpr->operand, context ) );

        return asmExpr;
}

const ast::AsmStmt * Resolver::previsit( const ast::AsmStmt * asmStmt ) {
        visitor->maybe_accept( asmStmt, &ast::AsmStmt::input );
        visitor->maybe_accept( asmStmt, &ast::AsmStmt::output );
        visit_children = false;
        return asmStmt;
}

const ast::IfStmt * Resolver::previsit( const ast::IfStmt * ifStmt ) {
        return ast::mutate_field(
                ifStmt, &ast::IfStmt::cond, findCondExpression( ifStmt->cond, context ) );
}

const ast::WhileDoStmt * Resolver::previsit( const ast::WhileDoStmt * whileDoStmt ) {
        return ast::mutate_field(
                whileDoStmt, &ast::WhileDoStmt::cond, findCondExpression( whileDoStmt->cond, context ) );
}

const ast::ForStmt * Resolver::previsit( const ast::ForStmt * forStmt ) {
        if ( forStmt->cond ) {
                forStmt = ast::mutate_field(
                        forStmt, &ast::ForStmt::cond, findCondExpression( forStmt->cond, context ) );
        }

        if ( forStmt->inc ) {
                forStmt = ast::mutate_field(
                        forStmt, &ast::ForStmt::inc, findVoidExpression( forStmt->inc, context ) );
        }

        return forStmt;
}

const ast::SwitchStmt * Resolver::previsit( const ast::SwitchStmt * switchStmt ) {
        GuardValue( currentObject );
        switchStmt = ast::mutate_field(
                switchStmt, &ast::SwitchStmt::cond,
                findIntegralExpression( switchStmt->cond, context ) );
        currentObject = ast::CurrentObject{ switchStmt->location, switchStmt->cond->result };
        return switchStmt;
}

const ast::CaseClause * Resolver::previsit( const ast::CaseClause * caseStmt ) {
        if ( caseStmt->cond ) {
                std::deque< ast::InitAlternative > initAlts = currentObject.getOptions();
                assertf( initAlts.size() == 1, "SwitchStmt did not correctly resolve an integral "
                        "expression." );

                ast::ptr< ast::Expr > untyped =
                        new ast::CastExpr{ caseStmt->location, caseStmt->cond, initAlts.front().type };
                ast::ptr< ast::Expr > newExpr = findSingleExpression( untyped, context );

                // case condition cannot have a cast in C, so it must be removed here, regardless of
                // whether it would perform a conversion.
                if ( const ast::CastExpr * castExpr = newExpr.as< ast::CastExpr >() ) {
                        swap_and_save_env( newExpr, castExpr->arg );
                }

                caseStmt = ast::mutate_field( caseStmt, &ast::CaseClause::cond, newExpr );
        }
        return caseStmt;
}

const ast::BranchStmt * Resolver::previsit( const ast::BranchStmt * branchStmt ) {
        visit_children = false;
        // must resolve the argument of a computed goto
        if ( branchStmt->kind == ast::BranchStmt::Goto && branchStmt->computedTarget ) {
                // computed goto argument is void*
                ast::ptr< ast::Type > target = new ast::PointerType{ new ast::VoidType{} };
                branchStmt = ast::mutate_field(
                        branchStmt, &ast::BranchStmt::computedTarget,
                        findSingleExpression( branchStmt->computedTarget, target, context ) );
        }
        return branchStmt;
}

const ast::ReturnStmt * Resolver::previsit( const ast::ReturnStmt * returnStmt ) {
        visit_children = false;
        if ( returnStmt->expr ) {
                returnStmt = ast::mutate_field(
                        returnStmt, &ast::ReturnStmt::expr,
                        findSingleExpression( returnStmt->expr, functionReturn, context ) );
        }
        return returnStmt;
}

const ast::ThrowStmt * Resolver::previsit( const ast::ThrowStmt * throwStmt ) {
        visit_children = false;
        if ( throwStmt->expr ) {
                const ast::StructDecl * exceptionDecl =
                        symtab.lookupStruct( "__cfaehm_base_exception_t" );
                assert( exceptionDecl );
                ast::ptr< ast::Type > exceptType =
                        new ast::PointerType{ new ast::StructInstType{ exceptionDecl } };
                throwStmt = ast::mutate_field(
                        throwStmt, &ast::ThrowStmt::expr,
                        findSingleExpression( throwStmt->expr, exceptType, context ) );
        }
        return throwStmt;
}

const ast::CatchClause * Resolver::previsit( const ast::CatchClause * catchClause ) {
        // Until we are very sure this invarent (ifs that move between passes have then)
        // holds, check it. This allows a check for when to decode the mangling.
        if ( auto ifStmt = catchClause->body.as<ast::IfStmt>() ) {
                assert( ifStmt->then );
        }
        // Encode the catchStmt so the condition can see the declaration.
        if ( catchClause->cond ) {
                ast::CatchClause * clause = mutate( catchClause );
                clause->body = new ast::IfStmt( clause->location, clause->cond, nullptr, clause->body );
                clause->cond = nullptr;
                return clause;
        }
        return catchClause;
}

const ast::CatchClause * Resolver::postvisit( const ast::CatchClause * catchClause ) {
        // Decode the catchStmt so everything is stored properly.
        const ast::IfStmt * ifStmt = catchClause->body.as<ast::IfStmt>();
        if ( nullptr != ifStmt && nullptr == ifStmt->then ) {
                assert( ifStmt->cond );
                assert( ifStmt->else_ );
                ast::CatchClause * clause = ast::mutate( catchClause );
                clause->cond = ifStmt->cond;
                clause->body = ifStmt->else_;
                // ifStmt should be implicately deleted here.
                return clause;
        }
        return catchClause;
}

const ast::WaitForStmt * Resolver::previsit( const ast::WaitForStmt * stmt ) {
        visit_children = false;

        // Resolve all clauses first
        for ( unsigned i = 0; i < stmt->clauses.size(); ++i ) {
                const ast::WaitForClause & clause = *stmt->clauses[i];

                ast::TypeEnvironment env;
                CandidateFinder funcFinder( context, env );

                // Find all candidates for a function in canonical form
                funcFinder.find( clause.target, ResolveMode::withAdjustment() );

                if ( funcFinder.candidates.empty() ) {
                        stringstream ss;
                        ss << "Use of undeclared indentifier '";
                        ss << clause.target.strict_as< ast::NameExpr >()->name;
                        ss << "' in call to waitfor";
                        SemanticError( stmt->location, ss.str() );
                }

                if ( clause.target_args.empty() ) {
                        SemanticError( stmt->location,
                                "Waitfor clause must have at least one mutex parameter");
                }

                // Find all alternatives for all arguments in canonical form
                std::vector< CandidateFinder > argFinders =
                        funcFinder.findSubExprs( clause.target_args );

                // List all combinations of arguments
                std::vector< CandidateList > possibilities;
                combos( argFinders.begin(), argFinders.end(), back_inserter( possibilities ) );

                // For every possible function:
                // * try matching the arguments to the parameters, not the other way around because
                //   more arguments than parameters
                CandidateList funcCandidates;
                std::vector< CandidateList > argsCandidates;
                SemanticErrorException errors;
                for ( CandidateRef & func : funcFinder.candidates ) {
                        try {
                                auto pointerType = dynamic_cast< const ast::PointerType * >(
                                        func->expr->result->stripReferences() );
                                if ( ! pointerType ) {
                                        SemanticError( stmt->location, func->expr->result.get(),
                                                "candidate not viable: not a pointer type\n" );
                                }

                                auto funcType = pointerType->base.as< ast::FunctionType >();
                                if ( ! funcType ) {
                                        SemanticError( stmt->location, func->expr->result.get(),
                                                "candidate not viable: not a function type\n" );
                                }

                                {
                                        auto param    = funcType->params.begin();
                                        auto paramEnd = funcType->params.end();

                                        if( ! nextMutex( param, paramEnd ) ) {
                                                SemanticError( stmt->location, funcType,
                                                        "candidate function not viable: no mutex parameters\n");
                                        }
                                }

                                CandidateRef func2{ new Candidate{ *func } };
                                // strip reference from function
                                func2->expr = referenceToRvalueConversion( func->expr, func2->cost );

                                // Each argument must be matched with a parameter of the current candidate
                                for ( auto & argsList : possibilities ) {
                                        try {
                                                // Declare data structures needed for resolution
                                                ast::OpenVarSet open;
                                                ast::AssertionSet need, have;
                                                ast::TypeEnvironment resultEnv{ func->env };
                                                // Add all type variables as open so that those not used in the
                                                // parameter list are still considered open
                                                resultEnv.add( funcType->forall );

                                                // load type variables from arguments into one shared space
                                                for ( auto & arg : argsList ) {
                                                        resultEnv.simpleCombine( arg->env );
                                                }

                                                // Make sure we don't widen any existing bindings
                                                resultEnv.forbidWidening();

                                                // Find any unbound type variables
                                                resultEnv.extractOpenVars( open );

                                                auto param = funcType->params.begin();
                                                auto paramEnd = funcType->params.end();

                                                unsigned n_mutex_param = 0;

                                                // For every argument of its set, check if it matches one of the
                                                // parameters. The order is important
                                                for ( auto & arg : argsList ) {
                                                        // Ignore non-mutex arguments
                                                        if ( ! nextMutex( param, paramEnd ) ) {
                                                                // We ran out of parameters but still have arguments.
                                                                // This function doesn't match
                                                                SemanticError( stmt->location, funcType,
                                                                        toString("candidate function not viable: too many mutex "
                                                                        "arguments, expected ", n_mutex_param, "\n" ) );
                                                        }

                                                        ++n_mutex_param;

                                                        // Check if the argument matches the parameter type in the current scope.
                                                        // ast::ptr< ast::Type > paramType = (*param)->get_type();

                                                        if (
                                                                ! unify(
                                                                        arg->expr->result, *param, resultEnv, need, have, open )
                                                        ) {
                                                                // Type doesn't match
                                                                stringstream ss;
                                                                ss << "candidate function not viable: no known conversion "
                                                                        "from '";
                                                                ast::print( ss, *param );
                                                                ss << "' to '";
                                                                ast::print( ss, arg->expr->result );
                                                                ss << "' with env '";
                                                                ast::print( ss, resultEnv );
                                                                ss << "'\n";
                                                                SemanticError( stmt->location, funcType, ss.str() );
                                                        }

                                                        ++param;
                                                }

                                                // All arguments match!

                                                // Check if parameters are missing
                                                if ( nextMutex( param, paramEnd ) ) {
                                                        do {
                                                                ++n_mutex_param;
                                                                ++param;
                                                        } while ( nextMutex( param, paramEnd ) );

                                                        // We ran out of arguments but still have parameters left; this
                                                        // function doesn't match
                                                        SemanticError( stmt->location, funcType,
                                                                toString( "candidate function not viable: too few mutex "
                                                                "arguments, expected ", n_mutex_param, "\n" ) );
                                                }

                                                // All parameters match!

                                                // Finish the expressions to tie in proper environments
                                                finishExpr( func2->expr, resultEnv );
                                                for ( CandidateRef & arg : argsList ) {
                                                        finishExpr( arg->expr, resultEnv );
                                                }

                                                // This is a match, store it and save it for later
                                                funcCandidates.emplace_back( std::move( func2 ) );
                                                argsCandidates.emplace_back( std::move( argsList ) );

                                        } catch ( SemanticErrorException & e ) {
                                                errors.append( e );
                                        }
                                }
                        } catch ( SemanticErrorException & e ) {
                                errors.append( e );
                        }
                }

                // Make sure correct number of arguments
                if( funcCandidates.empty() ) {
                        SemanticErrorException top( stmt->location,
                                "No alternatives for function in call to waitfor" );
                        top.append( errors );
                        throw top;
                }

                if( argsCandidates.empty() ) {
                        SemanticErrorException top( stmt->location,
                                "No alternatives for arguments in call to waitfor" );
                        top.append( errors );
                        throw top;
                }

                if( funcCandidates.size() > 1 ) {
                        SemanticErrorException top( stmt->location,
                                "Ambiguous function in call to waitfor" );
                        top.append( errors );
                        throw top;
                }
                if( argsCandidates.size() > 1 ) {
                        SemanticErrorException top( stmt->location,
                                "Ambiguous arguments in call to waitfor" );
                        top.append( errors );
                        throw top;
                }
                // TODO: need to use findDeletedExpr to ensure no deleted identifiers are used.

                // build new clause
                auto clause2 = new ast::WaitForClause( clause.location );

                clause2->target = funcCandidates.front()->expr;

                clause2->target_args.reserve( clause.target_args.size() );
                const ast::StructDecl * decl_monitor = symtab.lookupStruct( "monitor$" );
                for ( auto arg : argsCandidates.front() ) {
                        const auto & loc = stmt->location;

                        ast::Expr * init = new ast::CastExpr( loc,
                                new ast::UntypedExpr( loc,
                                        new ast::NameExpr( loc, "get_monitor" ),
                                        { arg->expr }
                                ),
                                new ast::PointerType(
                                        new ast::StructInstType(
                                                decl_monitor
                                        )
                                )
                        );

                        clause2->target_args.emplace_back( findSingleExpression( init, context ) );
                }

                // Resolve the conditions as if it were an IfStmt, statements normally
                clause2->when_cond = findCondExpression( clause.when_cond, context );
                clause2->stmt = clause.stmt->accept( *visitor );

                // set results into stmt
                auto n = mutate( stmt );
                n->clauses[i] = clause2;
                stmt = n;
        }

        if ( stmt->timeout_stmt ) {
                // resolve the timeout as a size_t, the conditions like IfStmt, and stmts normally
                ast::ptr< ast::Type > target =
                        new ast::BasicType{ ast::BasicKind::LongLongUnsignedInt };
                auto timeout_time = findSingleExpression( stmt->timeout_time, target, context );
                auto timeout_cond = findCondExpression( stmt->timeout_cond, context );
                auto timeout_stmt = stmt->timeout_stmt->accept( *visitor );

                // set results into stmt
                auto n = mutate( stmt );
                n->timeout_time = std::move( timeout_time );
                n->timeout_cond = std::move( timeout_cond );
                n->timeout_stmt = std::move( timeout_stmt );
                stmt = n;
        }

        if ( stmt->else_stmt ) {
                // resolve the condition like IfStmt, stmts normally
                auto else_cond = findCondExpression( stmt->else_cond, context );
                auto else_stmt = stmt->else_stmt->accept( *visitor );

                // set results into stmt
                auto n = mutate( stmt );
                n->else_cond = std::move( else_cond );
                n->else_stmt = std::move( else_stmt );
                stmt = n;
        }

        return stmt;
}

const ast::WithStmt * Resolver::previsit( const ast::WithStmt * withStmt ) {
        auto mutStmt = mutate(withStmt);
        resolveWithExprs(mutStmt->exprs, stmtsToAddBefore);
        return mutStmt;
}

void Resolver::resolveWithExprs(std::vector<ast::ptr<ast::Expr>> & exprs, std::list<ast::ptr<ast::Stmt>> & stmtsToAdd) {
        for (auto & expr : exprs) {
                // only struct- and union-typed expressions are viable candidates
                expr = findKindExpression( expr, context, structOrUnionOrEnum, "with expression" );

                // if with expression might be impure, create a temporary so that it is evaluated once
                if ( Tuples::maybeImpure( expr ) ) {
                        static UniqueName tmpNamer( "_with_tmp_" );
                        const CodeLocation loc = expr->location;
                        auto tmp = new ast::ObjectDecl(loc, tmpNamer.newName(), expr->result, new ast::SingleInit(loc, expr ) );
                        expr = new ast::VariableExpr( loc, tmp );
                        stmtsToAdd.push_back( new ast::DeclStmt(loc, tmp ) );
                        if ( InitTweak::isConstructable( tmp->type ) ) {
                                // generate ctor/dtor and resolve them
                                tmp->init = InitTweak::genCtorInit( loc, tmp );
                        }
                        // since tmp is freshly created, this should modify tmp in-place
                        tmp->accept( *visitor );
                } else if (expr->env && expr->env->empty()) {
                        expr = ast::mutate_field(expr.get(), &ast::Expr::env, nullptr);
                }
        }
}

const ast::SingleInit * Resolver::previsit( const ast::SingleInit * singleInit ) {
        visit_children = false;
        // resolve initialization using the possibilities as determined by the `currentObject`
        // cursor.
        ast::ptr< ast::Expr > untyped = new ast::UntypedInitExpr{
                singleInit->location, singleInit->value, currentObject.getOptions() };
        ast::ptr<ast::Expr> newExpr = findSingleExpression( untyped, context );
        const ast::InitExpr * initExpr = newExpr.strict_as< ast::InitExpr >();

        // move cursor to the object that is actually initialized
        currentObject.setNext( initExpr->designation );

        // discard InitExpr wrapper and retain relevant pieces.
        // `initExpr` may have inferred params in the case where the expression specialized a
        // function pointer, and newExpr may already have inferParams of its own, so a simple
        // swap is not sufficient
        ast::Expr::InferUnion inferred = initExpr->inferred;
        swap_and_save_env( newExpr, initExpr->expr );
        newExpr.get_and_mutate()->inferred.splice( std::move(inferred) );

        // get the actual object's type (may not exactly match what comes back from the resolver
        // due to conversions)
        const ast::Type * initContext = currentObject.getCurrentType();

        removeExtraneousCast( newExpr );

        // check if actual object's type is char[]
        if ( auto at = dynamic_cast< const ast::ArrayType * >( initContext ) ) {
                if ( isCharType( at->base ) ) {
                        // check if the resolved type is char*
                        if ( auto pt = newExpr->result.as< ast::PointerType >() ) {
                                if ( isCharType( pt->base ) ) {
                                        // strip cast if we're initializing a char[] with a char*
                                        // e.g. char x[] = "hello"
                                        if ( auto ce = newExpr.as< ast::CastExpr >() ) {
                                                swap_and_save_env( newExpr, ce->arg );
                                        }
                                }
                        }
                }
        }

        // move cursor to next object in preparation for next initializer
        currentObject.increment();

        // set initializer expression to resolved expression
        return ast::mutate_field( singleInit, &ast::SingleInit::value, std::move(newExpr) );
}

const ast::ListInit * Resolver::previsit( const ast::ListInit * listInit ) {
        // move cursor into brace-enclosed initializer-list
        currentObject.enterListInit( listInit->location );

        assert( listInit->designations.size() == listInit->initializers.size() );
        for ( unsigned i = 0; i < listInit->designations.size(); ++i ) {
                // iterate designations and initializers in pairs, moving the cursor to the current
                // designated object and resolving the initializer against that object
                listInit = ast::mutate_field_index(
                        listInit, &ast::ListInit::designations, i,
                        currentObject.findNext( listInit->designations[i] ) );
                listInit = ast::mutate_field_index(
                        listInit, &ast::ListInit::initializers, i,
                        listInit->initializers[i]->accept( *visitor ) );
        }

        // move cursor out of brace-enclosed initializer-list
        currentObject.exitListInit();

        visit_children = false;
        return listInit;
}

const ast::ConstructorInit * Resolver::previsit( const ast::ConstructorInit * ctorInit ) {
        visitor->maybe_accept( ctorInit, &ast::ConstructorInit::ctor );
        visitor->maybe_accept( ctorInit, &ast::ConstructorInit::dtor );

        // found a constructor - can get rid of C-style initializer
        // xxx - Rob suggests this field is dead code
        ctorInit = ast::mutate_field( ctorInit, &ast::ConstructorInit::init, nullptr );

        // intrinsic single-parameter constructors and destructors do nothing. Since this was
        // implicitly generated, there's no way for it to have side effects, so get rid of it to
        // clean up generated code
        if ( InitTweak::isIntrinsicSingleArgCallStmt( ctorInit->ctor ) ) {
                ctorInit = ast::mutate_field( ctorInit, &ast::ConstructorInit::ctor, nullptr );
        }
        if ( InitTweak::isIntrinsicSingleArgCallStmt( ctorInit->dtor ) ) {
                ctorInit = ast::mutate_field( ctorInit, &ast::ConstructorInit::dtor, nullptr );
        }

        return ctorInit;
}

// suppress error on autogen functions and mark invalid autogen as deleted.
bool Resolver::on_error(ast::ptr<ast::Decl> & decl) {
        if (auto functionDecl = decl.as<ast::FunctionDecl>()) {
                // xxx - can intrinsic gen ever fail?
                if (functionDecl->linkage == ast::Linkage::AutoGen) {
                        auto mutDecl = mutate(functionDecl);
                        mutDecl->isDeleted = true;
                        mutDecl->stmts = nullptr;
                        symtab.reviseSpecialAsDeleted( functionDecl );
                        decl = mutDecl;
                        return false;
                }
        }
        return true;
}

} // namespace ResolvExpr

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //