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Add method chaining (RFC ponylang#25)
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This change provides a way to chain calls on an object without
depending on the method's API.

Closes ponylang#1409.
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Benoit Vey committed Nov 10, 2016
1 parent 71c79f6 commit 92360aa
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Showing 13 changed files with 408 additions and 21 deletions.
6 changes: 6 additions & 0 deletions pony.g
Original file line number Diff line number Diff line change
Expand Up @@ -172,6 +172,10 @@ call
: '(' positional? named? ')'
;

chain
: '.>' ID
;

tilde
: '~' ID
;
Expand Down Expand Up @@ -330,13 +334,15 @@ antlr_1
antlr_2
: dot
| tilde
| chain
| typeargs
| call
;

antlr_3
: dot
| tilde
| chain
| typeargs
| call
;
Expand Down
4 changes: 4 additions & 0 deletions src/libponyc/ast/lexer.c
Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,8 @@ static const lextoken_t symbols[] =
{ "<=", TK_LE },
{ ">=", TK_GE },

{ ".>", TK_CHAIN },

{ "{", TK_LBRACE },
{ "}", TK_RBRACE },
{ "(", TK_LPAREN },
Expand Down Expand Up @@ -278,6 +280,8 @@ static const lextoken_t abstract[] =
{ "newapp", TK_NEWAPP },
{ "beapp", TK_BEAPP },
{ "funapp", TK_FUNAPP },
{ "bechain", TK_BECHAIN },
{ "funchain", TK_FUNCHAIN },

{ "\\n", TK_NEWLINE },
{NULL, (token_id)0}
Expand Down
15 changes: 11 additions & 4 deletions src/libponyc/ast/parser.c
Original file line number Diff line number Diff line change
Expand Up @@ -487,6 +487,13 @@ DEF(tilde);
TOKEN("method name", TK_ID);
DONE();

// CHAIN ID
DEF(chain);
INFIX_BUILD();
TOKEN(NULL, TK_CHAIN);
TOKEN("method name", TK_ID);
DONE();

// typeargs
DEF(qualify);
INFIX_BUILD();
Expand All @@ -504,16 +511,16 @@ DEF(call);
TERMINATE("call arguments", TK_RPAREN);
DONE();

// atom {dot | tilde | qualify | call}
// atom {dot | tilde | chain | qualify | call}
DEF(postfix);
RULE("value", atom);
SEQ("postfix expression", dot, tilde, qualify, call);
SEQ("postfix expression", dot, tilde, chain, qualify, call);
DONE();

// atom {dot | tilde | qualify | call}
// atom {dot | tilde | chain | qualify | call}
DEF(nextpostfix);
RULE("value", nextatom);
SEQ("postfix expression", dot, tilde, qualify, call);
SEQ("postfix expression", dot, tilde, chain, qualify, call);
DONE();

// (VAR | LET | EMBED | $LET) ID [COLON type]
Expand Down
3 changes: 3 additions & 0 deletions src/libponyc/ast/token.h
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ typedef enum token_id
TK_DBLARROW,
TK_DOT,
TK_TILDE,
TK_CHAIN,
TK_COLON,
TK_SEMI,
TK_ASSIGN,
Expand Down Expand Up @@ -237,6 +238,8 @@ typedef enum token_id
TK_NEWAPP,
TK_BEAPP,
TK_FUNAPP,
TK_BECHAIN,
TK_FUNCHAIN,

// Pseudo tokens that never actually exist
TK_NEWLINE, // Used by parser macros
Expand Down
8 changes: 8 additions & 0 deletions src/libponyc/codegen/gencall.c
Original file line number Diff line number Diff line change
Expand Up @@ -489,6 +489,8 @@ LLVMValueRef gen_call(compile_t* c, ast_t* ast)
case TK_NEWBEREF:
case TK_BEREF:
case TK_FUNREF:
case TK_BECHAIN:
case TK_FUNCHAIN:
typeargs = method;
AST_GET_CHILDREN_NO_DECL(receiver, receiver, method);
break;
Expand Down Expand Up @@ -600,6 +602,8 @@ LLVMValueRef gen_call(compile_t* c, ast_t* ast)

case TK_BEREF:
case TK_FUNREF:
case TK_BECHAIN:
case TK_FUNCHAIN:
args[0] = gen_expr(c, receiver);
break;

Expand Down Expand Up @@ -700,6 +704,10 @@ LLVMValueRef gen_call(compile_t* c, ast_t* ast)
(t->underlying == TK_CLASS))
r = args[0];

// Chained methods forward their receiver.
if((ast_id(postfix) == TK_BECHAIN) || (ast_id(postfix) == TK_FUNCHAIN))
r = args[0];

ponyint_pool_free_size(buf_size, args);
ponyint_pool_free_size(buf_size, params);
return r;
Expand Down
86 changes: 73 additions & 13 deletions src/libponyc/expr/call.c
Original file line number Diff line number Diff line change
Expand Up @@ -294,9 +294,23 @@ static bool check_arg_types(pass_opt_t* opt, ast_t* params, ast_t* positional,
static bool auto_recover_call(ast_t* ast, ast_t* receiver_type,
ast_t* positional, ast_t* result)
{
switch(ast_id(ast))
{
case TK_FUNREF:
case TK_FUNAPP:
case TK_FUNCHAIN:
break;

default:
assert(0);
break;
}

// We can recover the receiver (ie not alias the receiver type) if all
// arguments are safe and the result is either safe or unused.
if(is_result_needed(ast) && !safe_to_autorecover(receiver_type, result))
// The result of a chained method is always unused.
ast_t* call = ast_parent(ast);
if(is_result_needed(call) && !safe_to_autorecover(receiver_type, result))
return false;

ast_t* arg = ast_child(positional);
Expand Down Expand Up @@ -324,7 +338,21 @@ static bool auto_recover_call(ast_t* ast, ast_t* receiver_type,
return true;
}

static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast)
static ast_t* method_receiver_type(ast_t* method)
{
ast_t* receiver = ast_child(method);

// Dig through function qualification.
if((ast_id(receiver) == TK_FUNREF) || (ast_id(receiver) == TK_FUNAPP) ||
(ast_id(receiver) == TK_FUNCHAIN))
receiver = ast_child(receiver);

ast_t* r_type = ast_type(receiver);

return r_type;
}

static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast, bool* recovered)
{
AST_GET_CHILDREN(ast, positional, namedargs, lhs);

Expand All @@ -335,15 +363,8 @@ static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast)

AST_GET_CHILDREN(type, cap, typeparams, params, result);

// Check receiver cap.
ast_t* receiver = ast_child(lhs);

// Dig through function qualification.
if(ast_id(receiver) == TK_FUNREF || ast_id(receiver) == TK_FUNAPP)
receiver = ast_child(receiver);

// Receiver type, alias of receiver type, and target type.
ast_t* r_type = ast_type(receiver);
ast_t* r_type = method_receiver_type(lhs);

if(is_typecheck_error(r_type))
return false;
Expand All @@ -352,7 +373,7 @@ static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast)
ast_t* a_type;

// If we can recover the receiver, we don't alias it here.
bool can_recover = auto_recover_call(ast, r_type, positional, result);
bool can_recover = auto_recover_call(lhs, r_type, positional, result);
bool cap_recover = false;

switch(ast_id(cap))
Expand All @@ -373,9 +394,17 @@ static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast)
}

if(can_recover && cap_recover)
{
a_type = r_type;
if(recovered != NULL)
*recovered = true;
}
else
{
a_type = alias(r_type);
if(recovered != NULL)
*recovered = false;
}

errorframe_t info = NULL;
bool ok = is_subtype(a_type, t_type, &info, opt);
Expand All @@ -386,7 +415,7 @@ static bool check_receiver_cap(pass_opt_t* opt, ast_t* ast)

ast_error_frame(&frame, ast,
"receiver type is not a subtype of target type");
ast_error_frame(&frame, receiver,
ast_error_frame(&frame, ast_child(lhs),
"receiver type: %s", ast_print_type(a_type));
ast_error_frame(&frame, cap,
"target type: %s", ast_print_type(t_type));
Expand Down Expand Up @@ -437,7 +466,7 @@ static bool method_application(pass_opt_t* opt, ast_t* ast, bool partial)
{
case TK_FUNREF:
case TK_FUNAPP:
if(!check_receiver_cap(opt, ast))
if(!check_receiver_cap(opt, ast, NULL))
return false;
break;

Expand Down Expand Up @@ -688,6 +717,33 @@ static bool partial_application(pass_opt_t* opt, ast_t** astp)
return ast_passes_subtree(astp, opt, PASS_EXPR);
}

static bool method_chain(pass_opt_t* opt, ast_t* ast)
{
if(!method_application(opt, ast, false))
return false;

// We check the receiver cap now instead of in method_application because
// we need to know whether the receiver was recovered.
ast_t* lhs = ast_childidx(ast, 2);
ast_t* r_type = method_receiver_type(lhs);
if(ast_id(lhs) == TK_FUNCHAIN)
{
bool recovered;
if(!check_receiver_cap(opt, ast, &recovered))
return false;

ast_t* f_type = ast_type(lhs);
token_id f_cap = ast_id(ast_child(f_type));

ast_t* c_type = chain_type(r_type, f_cap, recovered);
ast_settype(ast, c_type);
} else {
ast_settype(ast, r_type);
}

return true;
}

bool expr_call(pass_opt_t* opt, ast_t** astp)
{
ast_t* ast = *astp;
Expand Down Expand Up @@ -717,6 +773,10 @@ bool expr_call(pass_opt_t* opt, ast_t** astp)
case TK_FUNAPP:
return partial_application(opt, astp);

case TK_BECHAIN:
case TK_FUNCHAIN:
return method_chain(opt, ast);

default: {}
}

Expand Down
3 changes: 2 additions & 1 deletion src/libponyc/expr/literal.c
Original file line number Diff line number Diff line change
Expand Up @@ -844,7 +844,8 @@ static bool unify(ast_t* ast, pass_opt_t* opt, bool report_errors)
bool literal_member_access(ast_t* ast, pass_opt_t* opt)
{
assert(ast != NULL);
assert(ast_id(ast) == TK_DOT || ast_id(ast) == TK_TILDE);
assert(ast_id(ast) == TK_DOT || ast_id(ast) == TK_TILDE ||
ast_id(ast) == TK_CHAIN);

AST_GET_CHILDREN(ast, receiver, name_node);

Expand Down
50 changes: 47 additions & 3 deletions src/libponyc/expr/postfix.c
Original file line number Diff line number Diff line change
Expand Up @@ -512,6 +512,8 @@ bool expr_qualify(pass_opt_t* opt, ast_t** astp)
case TK_NEWAPP:
case TK_BEAPP:
case TK_FUNAPP:
case TK_BECHAIN:
case TK_FUNCHAIN:
{
// Qualify the function.
assert(ast_id(type) == TK_FUNTYPE);
Expand Down Expand Up @@ -547,7 +549,7 @@ bool expr_qualify(pass_opt_t* opt, ast_t** astp)
return expr_qualify(opt, astp);
}

static bool dot_or_tilde(pass_opt_t* opt, ast_t** astp)
static bool entity_access(pass_opt_t* opt, ast_t** astp)
{
ast_t* ast = *astp;

Expand Down Expand Up @@ -588,12 +590,12 @@ static bool dot_or_tilde(pass_opt_t* opt, ast_t** astp)

bool expr_dot(pass_opt_t* opt, ast_t** astp)
{
return dot_or_tilde(opt, astp);
return entity_access(opt, astp);
}

bool expr_tilde(pass_opt_t* opt, ast_t** astp)
{
if(!dot_or_tilde(opt, astp))
if(!entity_access(opt, astp))
return false;

ast_t* ast = *astp;
Expand Down Expand Up @@ -639,3 +641,45 @@ bool expr_tilde(pass_opt_t* opt, ast_t** astp)
assert(0);
return false;
}

bool expr_chain(pass_opt_t* opt, ast_t** astp)
{
if(!entity_access(opt, astp))
return false;

ast_t* ast = *astp;

switch(ast_id(ast))
{
case TK_BEREF:
ast_setid(ast, TK_BECHAIN);
return true;

case TK_FUNREF:
ast_setid(ast, TK_FUNCHAIN);
return true;

case TK_NEWREF:
case TK_NEWBEREF:
ast_error(opt->check.errors, ast,
"can't do method chaining on a constructor");
return false;

case TK_TYPEREF:
ast_error(opt->check.errors, ast,
"can't do method chaining on a package");
return false;

case TK_FVARREF:
case TK_FLETREF:
case TK_EMBEDREF:
ast_error(opt->check.errors, ast,
"can't do method chaining on a field");
return false;

default: {}
}

assert(0);
return false;
}
1 change: 1 addition & 0 deletions src/libponyc/expr/postfix.h
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ PONY_EXTERN_C_BEGIN
bool expr_qualify(pass_opt_t* opt, ast_t** astp);
bool expr_dot(pass_opt_t* opt, ast_t** astp);
bool expr_tilde(pass_opt_t* opt, ast_t** astp);
bool expr_chain(pass_opt_t* opt, ast_t** astp);

PONY_EXTERN_C_END

Expand Down
6 changes: 6 additions & 0 deletions src/libponyc/pass/expr.c
Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,11 @@ bool is_result_needed(ast_t* ast)
// Result of a behaviour isn't needed.
return false;

case TK_BECHAIN:
case TK_FUNCHAIN:
// Result of a chained method isn't needed.
return false;

default: {}
}

Expand Down Expand Up @@ -258,6 +263,7 @@ ast_result_t pass_expr(ast_t** astp, pass_opt_t* options)
case TK_RECOVER: r = expr_recover(options, ast); break;
case TK_DOT: r = expr_dot(options, astp); break;
case TK_TILDE: r = expr_tilde(options, astp); break;
case TK_CHAIN: r = expr_chain(options, astp); break;
case TK_QUALIFY: r = expr_qualify(options, astp); break;
case TK_CALL: r = expr_call(options, astp); break;
case TK_IFDEF:
Expand Down
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