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Make parser LALR, conflict-free #11145

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Aug 4, 2024
Merged

Make parser LALR, conflict-free #11145

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429a197
parser.y: use names where I'll be refactoring
rhendric Jul 20, 2024
b0a8430
parser.y: move attr doc setting into addAttr
rhendric Jul 20, 2024
6e3b9e6
parser.y: eliminate conflicts
rhendric Jul 20, 2024
18db46a
parser.y: GLR -> LALR
rhendric Jul 22, 2024
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12 changes: 10 additions & 2 deletions src/libexpr/parser-state.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ struct StringToken
operator std::string_view() const { return {p, l}; }
};

// This type must be trivially copyable; see YYLTYPE_IS_TRIVIAL in parser.y.
struct ParserLocation
{
int beginOffset;
Expand Down Expand Up @@ -86,7 +87,7 @@ struct ParserState

void dupAttr(const AttrPath & attrPath, const PosIdx pos, const PosIdx prevPos);
void dupAttr(Symbol attr, const PosIdx pos, const PosIdx prevPos);
void addAttr(ExprAttrs * attrs, AttrPath && attrPath, Expr * e, const PosIdx pos);
void addAttr(ExprAttrs * attrs, AttrPath && attrPath, const ParserLocation & loc, Expr * e, const ParserLocation & exprLoc);
Formals * validateFormals(Formals * formals, PosIdx pos = noPos, Symbol arg = {});
Expr * stripIndentation(const PosIdx pos,
std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken>>> && es);
Expand All @@ -110,11 +111,12 @@ inline void ParserState::dupAttr(Symbol attr, const PosIdx pos, const PosIdx pre
});
}

inline void ParserState::addAttr(ExprAttrs * attrs, AttrPath && attrPath, Expr * e, const PosIdx pos)
inline void ParserState::addAttr(ExprAttrs * attrs, AttrPath && attrPath, const ParserLocation & loc, Expr * e, const ParserLocation & exprLoc)
{
AttrPath::iterator i;
// All attrpaths have at least one attr
assert(!attrPath.empty());
auto pos = at(loc);
// Checking attrPath validity.
// ===========================
for (i = attrPath.begin(); i + 1 < attrPath.end(); i++) {
Expand Down Expand Up @@ -179,6 +181,12 @@ inline void ParserState::addAttr(ExprAttrs * attrs, AttrPath && attrPath, Expr *
} else {
attrs->dynamicAttrs.push_back(ExprAttrs::DynamicAttrDef(i->expr, e, pos));
}

auto it = lexerState.positionToDocComment.find(pos);
if (it != lexerState.positionToDocComment.end()) {
e->setDocComment(it->second);
lexerState.positionToDocComment.emplace(at(exprLoc), it->second);
}
}

inline Formals * ParserState::validateFormals(Formals * formals, PosIdx pos, Symbol arg)
Expand Down
131 changes: 72 additions & 59 deletions src/libexpr/parser.y
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
%glr-parser
%define api.location.type { ::nix::ParserLocation }
%define api.pure
%locations
%define parse.error verbose
Expand All @@ -8,8 +8,7 @@
%parse-param { nix::ParserState * state }
%lex-param { void * scanner }
%lex-param { nix::ParserState * state }
%expect 1
%expect-rr 1
%expect 0

%code requires {

Expand All @@ -27,7 +26,17 @@
#include "eval-settings.hh"
#include "parser-state.hh"

#define YYLTYPE ::nix::ParserLocation
// Bison seems to have difficulty growing the parser stack when using C++ with
// a custom location type. This undocumented macro tells Bison that our
// location type is "trivially copyable" in C++-ese, so it is safe to use the
// same memcpy macro it uses to grow the stack that it uses with its own
// default location type. Without this, we get "error: memory exhausted" when
// parsing some large Nix files. Our other options are to increase the initial
// stack size (200 by default) to be as large as we ever want to support (so
// that growing the stack is unnecessary), or redefine the stack-relocation
// macro ourselves (which is also undocumented).
#define YYLTYPE_IS_TRIVIAL 1

#define YY_DECL int yylex \
(YYSTYPE * yylval_param, YYLTYPE * yylloc_param, yyscan_t yyscanner, nix::ParserState * state)

Expand Down Expand Up @@ -77,7 +86,7 @@ YY_DECL;

using namespace nix;

#define CUR_POS state->at(*yylocp)
#define CUR_POS state->at(yyloc)


void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char * error)
Expand Down Expand Up @@ -133,8 +142,8 @@ static Expr * makeCall(PosIdx pos, Expr * fn, Expr * arg) {
%type <e> expr_select expr_simple expr_app
%type <e> expr_pipe_from expr_pipe_into
%type <list> expr_list
%type <attrs> binds
%type <formals> formals
%type <attrs> binds binds1
%type <formals> formals formal_set
%type <formal> formal
%type <attrNames> attrpath
%type <inheritAttrs> attrs
Expand Down Expand Up @@ -180,22 +189,22 @@ expr_function
$$ = me;
SET_DOC_POS(me, @1);
}
| '{' formals '}' ':' expr_function
{ auto me = new ExprLambda(CUR_POS, state->validateFormals($2), $5);
| formal_set ':' expr_function[body]
{ auto me = new ExprLambda(CUR_POS, state->validateFormals($formal_set), $body);
$$ = me;
SET_DOC_POS(me, @1);
}
| '{' formals '}' '@' ID ':' expr_function
| formal_set '@' ID ':' expr_function[body]
{
auto arg = state->symbols.create($5);
auto me = new ExprLambda(CUR_POS, arg, state->validateFormals($2, CUR_POS, arg), $7);
auto arg = state->symbols.create($ID);
auto me = new ExprLambda(CUR_POS, arg, state->validateFormals($formal_set, CUR_POS, arg), $body);
$$ = me;
SET_DOC_POS(me, @1);
}
| ID '@' '{' formals '}' ':' expr_function
| ID '@' formal_set ':' expr_function[body]
{
auto arg = state->symbols.create($1);
auto me = new ExprLambda(CUR_POS, arg, state->validateFormals($4, CUR_POS, arg), $7);
auto arg = state->symbols.create($ID);
auto me = new ExprLambda(CUR_POS, arg, state->validateFormals($formal_set, CUR_POS, arg), $body);
$$ = me;
SET_DOC_POS(me, @1);
}
Expand Down Expand Up @@ -311,11 +320,13 @@ expr_simple
/* Let expressions `let {..., body = ...}' are just desugared
into `(rec {..., body = ...}).body'. */
| LET '{' binds '}'
{ $3->recursive = true; $$ = new ExprSelect(noPos, $3, state->s.body); }
{ $3->recursive = true; $3->pos = CUR_POS; $$ = new ExprSelect(noPos, $3, state->s.body); }
| REC '{' binds '}'
{ $3->recursive = true; $$ = $3; }
| '{' binds '}'
{ $$ = $2; }
{ $3->recursive = true; $3->pos = CUR_POS; $$ = $3; }
| '{' binds1 '}'
{ $2->pos = CUR_POS; $$ = $2; }
| '{' '}'
{ $$ = new ExprAttrs(CUR_POS); }
| '[' expr_list ']' { $$ = $2; }
;

Expand Down Expand Up @@ -364,52 +375,50 @@ ind_string_parts
;

binds
: binds attrpath '=' expr ';' {
$$ = $1;

auto pos = state->at(@2);
auto exprPos = state->at(@4);
{
auto it = state->lexerState.positionToDocComment.find(pos);
if (it != state->lexerState.positionToDocComment.end()) {
$4->setDocComment(it->second);
state->lexerState.positionToDocComment.emplace(exprPos, it->second);
}
}
: binds1
| { $$ = new ExprAttrs; }
;

state->addAttr($$, std::move(*$2), $4, pos);
delete $2;
binds1
: binds1[accum] attrpath '=' expr ';'
{ $$ = $accum;
state->addAttr($$, std::move(*$attrpath), @attrpath, $expr, @expr);
delete $attrpath;
}
| binds INHERIT attrs ';'
{ $$ = $1;
for (auto & [i, iPos] : *$3) {
if ($$->attrs.find(i.symbol) != $$->attrs.end())
state->dupAttr(i.symbol, iPos, $$->attrs[i.symbol].pos);
$$->attrs.emplace(
| binds[accum] INHERIT attrs ';'
{ $$ = $accum;
for (auto & [i, iPos] : *$attrs) {
if ($accum->attrs.find(i.symbol) != $accum->attrs.end())
state->dupAttr(i.symbol, iPos, $accum->attrs[i.symbol].pos);
$accum->attrs.emplace(
i.symbol,
ExprAttrs::AttrDef(new ExprVar(iPos, i.symbol), iPos, ExprAttrs::AttrDef::Kind::Inherited));
}
delete $3;
delete $attrs;
}
| binds INHERIT '(' expr ')' attrs ';'
{ $$ = $1;
if (!$$->inheritFromExprs)
$$->inheritFromExprs = std::make_unique<std::vector<Expr *>>();
$$->inheritFromExprs->push_back($4);
auto from = new nix::ExprInheritFrom(state->at(@4), $$->inheritFromExprs->size() - 1);
for (auto & [i, iPos] : *$6) {
if ($$->attrs.find(i.symbol) != $$->attrs.end())
state->dupAttr(i.symbol, iPos, $$->attrs[i.symbol].pos);
$$->attrs.emplace(
| binds[accum] INHERIT '(' expr ')' attrs ';'
{ $$ = $accum;
if (!$accum->inheritFromExprs)
$accum->inheritFromExprs = std::make_unique<std::vector<Expr *>>();
$accum->inheritFromExprs->push_back($expr);
auto from = new nix::ExprInheritFrom(state->at(@expr), $accum->inheritFromExprs->size() - 1);
for (auto & [i, iPos] : *$attrs) {
if ($accum->attrs.find(i.symbol) != $accum->attrs.end())
state->dupAttr(i.symbol, iPos, $accum->attrs[i.symbol].pos);
$accum->attrs.emplace(
i.symbol,
ExprAttrs::AttrDef(
new ExprSelect(iPos, from, i.symbol),
iPos,
ExprAttrs::AttrDef::Kind::InheritedFrom));
}
delete $6;
delete $attrs;
}
| attrpath '=' expr ';'
{ $$ = new ExprAttrs;
state->addAttr($$, std::move(*$attrpath), @attrpath, $expr, @expr);
delete $attrpath;
}
| { $$ = new ExprAttrs(state->at(@0)); }
;

attrs
Expand Down Expand Up @@ -467,15 +476,19 @@ expr_list
| { $$ = new ExprList; }
;

formal_set
: '{' formals ',' ELLIPSIS '}' { $$ = $formals; $$->ellipsis = true; }
| '{' ELLIPSIS '}' { $$ = new Formals; $$->ellipsis = true; }
| '{' formals ',' '}' { $$ = $formals; $$->ellipsis = false; }
| '{' formals '}' { $$ = $formals; $$->ellipsis = false; }
| '{' '}' { $$ = new Formals; $$->ellipsis = false; }
;

formals
: formal ',' formals
{ $$ = $3; $$->formals.emplace_back(*$1); delete $1; }
: formals[accum] ',' formal
{ $$ = $accum; $$->formals.emplace_back(*$formal); delete $formal; }
| formal
{ $$ = new Formals; $$->formals.emplace_back(*$1); $$->ellipsis = false; delete $1; }
|
{ $$ = new Formals; $$->ellipsis = false; }
| ELLIPSIS
{ $$ = new Formals; $$->ellipsis = true; }
{ $$ = new Formals; $$->formals.emplace_back(*$formal); delete $formal; }
;

formal
Expand Down
2 changes: 1 addition & 1 deletion tests/functional/lang/parse-fail-undef-var-2.err.exp
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
error: syntax error, unexpected ':', expecting '}'
error: syntax error, unexpected ':', expecting '}' or ','
at «stdin»:3:13:
2|
3| f = {x, y : ["baz" "bar" z "bat"]}: x + y;
Expand Down
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