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Diffstat (limited to 'third_party/nix/src/libexpr/nixexpr.hh')
| -rw-r--r-- | third_party/nix/src/libexpr/nixexpr.hh | 361 |
1 files changed, 361 insertions, 0 deletions
diff --git a/third_party/nix/src/libexpr/nixexpr.hh b/third_party/nix/src/libexpr/nixexpr.hh new file mode 100644 index 0000000000..16b58dec2e --- /dev/null +++ b/third_party/nix/src/libexpr/nixexpr.hh @@ -0,0 +1,361 @@ +#pragma once + +#include <map> +#include <optional> +#include <variant> + +#include <absl/container/flat_hash_map.h> + +#include "libexpr/symbol-table.hh" +#include "libexpr/value.hh" +#include "libutil/types.hh" // TODO(tazjin): audit this include + +namespace nix { + +MakeError(EvalError, Error); +MakeError(ParseError, Error); +MakeError(AssertionError, EvalError); +MakeError(ThrownError, AssertionError); +MakeError(Abort, EvalError); +MakeError(TypeError, EvalError); +MakeError(UndefinedVarError, Error); +MakeError(RestrictedPathError, Error); + +/* Position objects. */ + +struct Pos { + std::optional<Symbol> file; + unsigned int line, column; + Pos(const std::optional<Symbol>& file, unsigned int line, unsigned int column) + : file(file), line(line), column(column){}; + + // TODO(tazjin): remove this - empty pos is never useful + Pos() : file(std::nullopt), line(0), column(0){}; + + operator bool() const { return line != 0; } + + bool operator<(const Pos& p2) const { + if (!file.has_value()) { + return true; + } + + if (!line) { + return p2.line; + } + if (!p2.line) { + return false; + } + int d = ((std::string)file.value()).compare((std::string)p2.file.value()); + if (d < 0) { + return true; + } + if (d > 0) { + return false; + } + if (line < p2.line) { + return true; + } + if (line > p2.line) { + return false; + } + return column < p2.column; + } +}; + +extern Pos noPos; + +std::ostream& operator<<(std::ostream& str, const Pos& pos); + +struct Env; +struct Value; +class EvalState; +struct StaticEnv; + +/* An attribute path is a sequence of attribute names. */ +using AttrName = std::variant<Symbol, Expr*>; +using AttrPath = std::vector<AttrName>; +using AttrNameVector = std::vector<AttrName>; + +using VectorExprs = std::vector<nix::Expr*>; + +std::string showAttrPath(const AttrPath& attrPath); + +/* Abstract syntax of Nix expressions. */ + +struct Expr { + virtual ~Expr(){}; + virtual void show(std::ostream& str) const; + virtual void bindVars(const StaticEnv& env); + virtual void eval(EvalState& state, Env& env, Value& v); + virtual Value* maybeThunk(EvalState& state, Env& env); +}; + +std::ostream& operator<<(std::ostream& str, const Expr& e); + +#define COMMON_METHODS \ + void show(std::ostream& str) const; \ + void eval(EvalState& state, Env& env, Value& v); \ + void bindVars(const StaticEnv& env); + +struct ExprInt : Expr { + NixInt n; + Value v; + ExprInt(NixInt n) : n(n) { mkInt(v, n); }; + COMMON_METHODS + Value* maybeThunk(EvalState& state, Env& env); +}; + +struct ExprFloat : Expr { + NixFloat nf; + Value v; + ExprFloat(NixFloat nf) : nf(nf) { mkFloat(v, nf); }; + COMMON_METHODS + Value* maybeThunk(EvalState& state, Env& env); +}; + +struct ExprString : Expr { + Symbol s; + Value v; + ExprString(const Symbol& s) : s(s) { mkString(v, s); }; + COMMON_METHODS + Value* maybeThunk(EvalState& state, Env& env); +}; + +/* Temporary class used during parsing of indented strings. */ +struct ExprIndStr : Expr { + std::string s; + ExprIndStr(const std::string& s) : s(s){}; +}; + +struct ExprPath : Expr { + std::string s; + Value v; + ExprPath(const std::string& s) : s(s) { mkPathNoCopy(v, this->s.c_str()); }; + COMMON_METHODS + Value* maybeThunk(EvalState& state, Env& env); +}; + +struct ExprVar : Expr { + Pos pos; + Symbol name; + + /* Whether the variable comes from an environment (e.g. a rec, let + or function argument) or from a "with". */ + bool fromWith; + + /* In the former case, the value is obtained by going `level' + levels up from the current environment and getting the + `displ'th value in that environment. In the latter case, the + value is obtained by getting the attribute named `name' from + the set stored in the environment that is `level' levels up + from the current one.*/ + unsigned int level; + unsigned int displ; + + ExprVar(const Symbol& name) : name(name){}; + ExprVar(const Pos& pos, const Symbol& name) : pos(pos), name(name){}; + COMMON_METHODS + Value* maybeThunk(EvalState& state, Env& env); +}; + +// [tazjin] I *think* that this struct describes the syntactic +// construct for "selecting" something out of an attribute set, e.g. +// `a.b.c` => ExprSelect{"b", "c"}. +// +// Each path element has got a pointer to an expression, which seems +// to be the thing preceding its period, but afaict that is only set +// for the first one in a path. +struct ExprSelect : Expr { + Pos pos; + Expr *e, *def; + AttrPath attrPath; + ExprSelect(const Pos& pos, Expr* e, const AttrPath& attrPath, Expr* def) + : pos(pos), e(e), def(def), attrPath(attrPath){}; + ExprSelect(const Pos& pos, Expr* e, const Symbol& name) + : pos(pos), e(e), def(0) { + attrPath.push_back(AttrName(name)); + }; + COMMON_METHODS +}; + +struct ExprOpHasAttr : Expr { + Pos pos; + Expr* e; + AttrPath attrPath; + ExprOpHasAttr(Expr* e, const AttrPath& attrPath) : e(e), attrPath(attrPath){}; + ExprOpHasAttr(const Pos& pos, Expr* e, const AttrPath& attrPath) + : pos(pos), e(e), attrPath(attrPath){}; + COMMON_METHODS +}; + +struct ExprAttrs : Expr { + bool recursive; + + struct AttrDef { + bool inherited; + Expr* e; + Pos pos; + unsigned int displ; // displacement + AttrDef(Expr* e, const Pos& pos, bool inherited = false) + : inherited(inherited), e(e), pos(pos), displ(0){}; + AttrDef(){}; + }; + + using AttrDefs = absl::flat_hash_map<Symbol, AttrDef>; + AttrDefs attrs; + + struct DynamicAttrDef { + Expr *nameExpr, *valueExpr; + Pos pos; + DynamicAttrDef(Expr* nameExpr, Expr* valueExpr, const Pos& pos) + : nameExpr(nameExpr), valueExpr(valueExpr), pos(pos){}; + }; + + using DynamicAttrDefs = std::vector<DynamicAttrDef>; + DynamicAttrDefs dynamicAttrs; + + ExprAttrs() : recursive(false){}; + COMMON_METHODS +}; + +struct ExprList : Expr { + VectorExprs elems; + ExprList(){}; + COMMON_METHODS +}; + +struct Formal { + Symbol name; + Expr* def; // def = default, not definition + Formal(const Symbol& name, Expr* def) : name(name), def(def){}; +}; + +// Describes structured function arguments (e.g. `{ a }: ...`) +struct Formals { + using Formals_ = std::list<Formal>; + Formals_ formals; + std::set<Symbol> argNames; // used during parsing + bool ellipsis; +}; + +struct ExprLambda : Expr { + public: + Pos pos; + std::optional<Symbol> name; + Symbol arg; + bool matchAttrs; + Formals* formals; + Expr* body; + ExprLambda(const Pos& pos, const Symbol& arg, bool matchAttrs, + Formals* formals, Expr* body) + : pos(pos), + arg(arg), + matchAttrs(matchAttrs), + formals(formals), + body(body) { + if (!arg.empty() && formals && + formals->argNames.find(arg) != formals->argNames.end()) { + throw ParseError( + format("duplicate formal function argument '%1%' at %2%") % arg % + pos); + } + }; + void setName(Symbol& name); + std::string showNamePos() const; + COMMON_METHODS +}; + +struct ExprLet : Expr { + ExprAttrs* attrs; + Expr* body; + ExprLet(ExprAttrs* attrs, Expr* body) : attrs(attrs), body(body){}; + COMMON_METHODS +}; + +struct ExprWith : Expr { + Pos pos; + Expr *attrs, *body; + size_t prevWith; + ExprWith(const Pos& pos, Expr* attrs, Expr* body) + : pos(pos), attrs(attrs), body(body){}; + COMMON_METHODS +}; + +struct ExprIf : Expr { + Pos pos; + Expr *cond, *then, *else_; + ExprIf(Expr* cond, Expr* then, Expr* else_) + : cond(cond), then(then), else_(else_){}; + ExprIf(const Pos& pos, Expr* cond, Expr* then, Expr* else_) + : pos(pos), cond(cond), then(then), else_(else_){}; + COMMON_METHODS +}; + +struct ExprAssert : Expr { + Pos pos; + Expr *cond, *body; + ExprAssert(const Pos& pos, Expr* cond, Expr* body) + : pos(pos), cond(cond), body(body){}; + COMMON_METHODS +}; + +struct ExprOpNot : Expr { + Pos pos; + Expr* e; + explicit ExprOpNot(Expr* e) : e(e){}; + ExprOpNot(const Pos& pos, Expr* e) : pos(pos), e(e){}; + COMMON_METHODS +}; + +#define MakeBinOp(name, s) \ + struct name : Expr { \ + Pos pos; \ + Expr *e1, *e2; \ + name(Expr* e1, Expr* e2) : e1(e1), e2(e2){}; \ + name(const Pos& pos, Expr* e1, Expr* e2) : pos(pos), e1(e1), e2(e2){}; \ + void show(std::ostream& str) const { \ + str << "(" << *e1 << " " s " " << *e2 << ")"; \ + } \ + void bindVars(const StaticEnv& env) { \ + e1->bindVars(env); \ + e2->bindVars(env); \ + } \ + void eval(EvalState& state, Env& env, Value& v); \ + }; + +MakeBinOp(ExprApp, ""); +MakeBinOp(ExprOpEq, "=="); +MakeBinOp(ExprOpNEq, "!="); +MakeBinOp(ExprOpAnd, "&&"); +MakeBinOp(ExprOpOr, "||"); +MakeBinOp(ExprOpImpl, "->"); +MakeBinOp(ExprOpUpdate, "//"); +MakeBinOp(ExprOpConcatLists, "++"); + +struct ExprConcatStrings : Expr { + Pos pos; + bool forceString; + nix::VectorExprs* es; + ExprConcatStrings(const Pos& pos, bool forceString, nix::VectorExprs* es) + : pos(pos), forceString(forceString), es(es){}; + COMMON_METHODS +}; + +struct ExprPos : Expr { + Pos pos; + ExprPos(const Pos& pos) : pos(pos){}; + COMMON_METHODS +}; + +/* Static environments are used to map variable names onto (level, + displacement) pairs used to obtain the value of the variable at + runtime. */ +struct StaticEnv { + bool isWith; + const StaticEnv* up; + typedef absl::flat_hash_map<Symbol, unsigned int> Vars; + Vars vars; + StaticEnv(bool isWith, const StaticEnv* up) : isWith(isWith), up(up){}; +}; + +} // namespace nix |