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xo-expression xo-reader: parser improvements, prep type inf/unify

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This commit is contained in:
Roland Conybeare 2025-07-28 09:12:41 -04:00
commit f3fde735da
18 changed files with 274 additions and 45 deletions
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58
xo-reader/src/reader/lambda_xs.cpp
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@ -1,6 +1,7 @@
/* @file lambda_xs.cpp */
#include "lambda_xs.hpp"
#include "define_xs.hpp"
#include "parserstatemachine.hpp"
#include "exprstatestack.hpp"
#include "expect_formal_arglist_xs.hpp"
@ -156,9 +157,55 @@ namespace xo {
{
constexpr const char * c_self_name = "lambda_xs::on_typedescr";
assert(td);
if (lmxs_type_ == lambdastatetype::lm_3) {
this->lmxs_type_ = lambdastatetype::lm_4;
this->explicit_return_td_ = td;
this->lambda_td_ = Lambda::assemble_lambda_td(local_env_->argv(),
explicit_return_td_);
/* 1. at this point we know function signature (@ref lambda_td_)
* 2. if this lambda appears on the rhs of a define,
* propagate function signature to the define.
* 3. this makes recursive function definitions like this work
* without relying on type inference:
* def fact = lambda (n : i64) : i64 {
* if (n == 0) then
* 1
* else
* n * fact(n - 1)
* }
* 4. while parsing the body of the lambda, we want environment
* to already associate the lambda's signature with variable 'fact',
* so that when parser encounters 'fact(n - 1)' the expression has
* known valuetype.
*/
if ((p_psm->exprstate_stack_size() >= 3)
&& (p_psm->lookup_exprstate(1).exs_type() == exprstatetype::expect_rhs_expression)
&& (p_psm->lookup_exprstate(2).exs_type() == exprstatetype::defexpr)
&& (p_psm->env_stack_size() >= 2)
)
{
bp<LocalEnv> def_env = p_psm->lookup_envframe(1);
assert(def_env->n_arg() == 1);
bp<Variable> def_var = def_env->lookup_arg(0).get();
if (def_var->valuetype() == nullptr) {
def_var->assign_valuetype(lambda_td_);
} else {
/* don't need to unify here. if def already hasa a type,
* that's because it was explicitly specified.
* will discover any conflict after reporting parsed lambda
* to define_xs
*/
}
}
expect_expr_xs::start(p_psm);
/* control reenters via .on_expr() or .on_expr_with_semicolon() */
} else {
@ -194,7 +241,16 @@ namespace xo {
/* top env frame recorded arguments to this lambda */
p_psm->pop_envframe();
rp<Lambda> lm = Lambda::make_from_env(name, local_env_, explicit_return_td_, body_);
rp<Lambda> lm;
/* TODO: unify explicit_return_td_ with body_ */
if (lambda_td_) {
lm = Lambda::make(name, lambda_td_, local_env_, body_);
} else {
lm = Lambda::make_from_env(name, local_env_,
explicit_return_td_, body_);
}
p_psm->top_exprstate().on_expr(lm, p_psm);
p_psm->top_exprstate().on_semicolon_token(tk, p_psm);