//
// 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 )
			) {
				// 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, ResolveMode::withAdjustment() );

	// 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 structOrUnion( const Candidate & i ) {
		const ast::Type * t = i.expr->result->stripReferences();
		return dynamic_cast< const ast::StructInstType * >( t ) || dynamic_cast< const ast::UnionInstType * >( 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;
	}
}

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);
			paramTypes.emplace_back(param->get_type());
		}
		for (auto & ret : mutDecl->returns) {
			ret = fixObjectType(ret.strict_as<ast::ObjectDecl>(), context);
			returnTypes.emplace_back(ret->get_type());
		}
		// 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 ) {
	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;
		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, structOrUnion, "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;
			decl = mutDecl;
			return false;
		}
	}
	return true;
}

} // namespace ResolvExpr

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