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UFCS: add method chaining #17

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0f45579
UFCS: add chaining to the UFCS calls
filipsajdak Sep 25, 2022
b035008
Add method chaining example to regression tests
filipsajdak Sep 25, 2022
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28 changes: 28 additions & 0 deletions regression-tests/mixed-ufcs-method-chaining.cpp2
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Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
#include <vector>

add: (in v : _, in a : int) -> auto = {
cv := v;
for cv do :(inout e : _) = {
e += a;
}
return cv;
}

dbl: (in v : _) -> auto = {
cv := v;
for cv do :(inout e : _) = {
e *= 2;
}
return cv;
}

main: () -> int = {

v : std::vector<int> = (1,2,3,4,5,6,7,8,9,10);

for v.dbl().add(1).dbl() do :(in e : _) = {
std::cout << e << ", ";
}

std::cout << std::endl;
}
88 changes: 53 additions & 35 deletions source/cppfront.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1667,17 +1667,19 @@ class cppfront
captured_part += "_" + std::to_string(mynum);
}

// Check to see if it's just a function call with "." syntax,
// Check to see if it's just a function call with "." syntax (potentially chained with other methods),
// and if so use this path to convert it to UFCS
if (// there's a single-token expression followed by . and (
n.expr->get_token() && // if the base expression is a single token
std::ssize(n.ops) >= 2 && // and we're of the form:
n.ops[0].op->type() == lexeme::Dot && // token . id-expr ( expr-list )
n.ops[1].op->type() == lexeme::LeftParen &&
// and either there's nothing after that, or there's just a $ after that
// or there is mathod chaining started
(
std::ssize(n.ops) == 2 ||
(std::ssize(n.ops) == 3 && n.ops[2].op->type() == lexeme::Dollar)
(std::ssize(n.ops) == 3 && n.ops[2].op->type() == lexeme::Dollar) ||
(std::ssize(n.ops) > 3 && n.ops[2].op->type() == lexeme::Dot) // fsajdak: chaining identification
)
)
{
Expand All @@ -1690,44 +1692,60 @@ class cppfront

// Otherwise, do the UFCS work...

// The . has its id_expr
assert (n.ops[0].id_expr);

// The ( has its expr_list and op_close
assert (n.ops[1].expr_list && n.ops[1].op_close);

//--------------------------------------------------------------------
// TODO: When MSVC supports __VA_OPT__ in standard mode without the
// experimental /Zc:preprocessor switch, use this single line
// instead of the dual lines below that special-case _0 args
// AND: Make the similarly noted change in cpp2util.h
//
//printer.print_cpp2("CPP2_UFCS(", n.position());
auto find_id_of_a_last = [](auto& ops, auto op){
for (int i = std::ssize(ops)-1; i>0; --i) {
if (ops[i].op->type() == op)
return i;
}
return 0;
};

// If there are no additional arguments, use the CPP2_UFCS_0 version
if (!n.ops[1].expr_list->expressions.empty()) {
printer.print_cpp2("CPP2_UFCS(", n.position());
}
else {
printer.print_cpp2("CPP2_UFCS_0(", n.position());
// If method are chained we need to go from the last to the first
// token.a(a-expr-list).b(b-expr-list).c(c-expr-list) will be tranformed to:
// CPP2_UFCS(c, CPP2_UFCS(b, CPP2_UFCS(a,token, a-expr-list), b-expr-list), c-expr-list )
for (auto i = find_id_of_a_last(n.ops, lexeme::LeftParen); i > 0; i -= 2)
{
// The . has its id_expr
assert (n.ops[i-1].id_expr);

// The ( has its expr_list and op_close
assert (n.ops[i].expr_list && n.ops[i].op_close);

//--------------------------------------------------------------------
// TODO: When MSVC supports __VA_OPT__ in standard mode without the
// experimental /Zc:preprocessor switch, use this single line
// instead of the dual lines below that special-case _0 args
// AND: Make the similarly noted change in cpp2util.h
//
//printer.print_cpp2("CPP2_UFCS(", n.position());

// If there are no additional arguments, use the CPP2_UFCS_0 version
if (!n.ops[i].expr_list->expressions.empty()) {
printer.print_cpp2("CPP2_UFCS(", n.position());
}
else {
printer.print_cpp2("CPP2_UFCS_0(", n.position());
}
emit(*n.ops[i-1].id_expr);
printer.print_cpp2(", ", n.position());
}
//--------------------------------------------------------------------

// Make the "funcname" the first argument to CPP2_UFCS
emit(*n.ops[0].id_expr);
printer.print_cpp2(", ", n.position());

// Then make the base expression the second argument
emit(*n.expr);
// expr-list need to be added in reversed order then CPP2_UFCS macros
for (auto i = 0; i < find_id_of_a_last(n.ops, lexeme::LeftParen); i += 2) {
// Then make the base expression the second argument - only needed on the most nested call
if (i == 0) {
emit(*n.expr);
}

// Then tack on any additional arguments
if (!n.ops[1].expr_list->expressions.empty()) {
printer.print_cpp2(", ", n.position());
push_need_expression_list_parens(false);
emit(*n.ops[1].expr_list);
pop_need_expression_list_parens();
// Then tack on any additional arguments
if (!n.ops[(i+1)].expr_list->expressions.empty()) {
printer.print_cpp2(", ", n.position());
push_need_expression_list_parens(false);
emit(*n.ops[(i+1)].expr_list);
pop_need_expression_list_parens();
}
printer.print_cpp2(")", n.position());
}
printer.print_cpp2(")", n.position());

// And we're done. This path has handled this node, so return...
return;
Expand Down