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|
use crate::hir::map as hir_map;
use crate::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
use crate::session::{config, Session};
use crate::session::config::EntryFnType;
use syntax::attr;
use syntax::entry::EntryPointType;
use syntax_pos::Span;
use crate::hir::{HirId, Item, ItemKind, ImplItem, TraitItem};
use crate::hir::itemlikevisit::ItemLikeVisitor;
use crate::ty::TyCtxt;
use crate::ty::query::Providers;
struct EntryContext<'a, 'tcx: 'a> {
session: &'a Session,
map: &'a hir_map::Map<'tcx>,
// The top-level function called 'main'
main_fn: Option<(HirId, Span)>,
// The function that has attribute named 'main'
attr_main_fn: Option<(HirId, Span)>,
// The function that has the attribute 'start' on it
start_fn: Option<(HirId, Span)>,
// The functions that one might think are 'main' but aren't, e.g.
// main functions not defined at the top level. For diagnostics.
non_main_fns: Vec<(HirId, Span)> ,
}
impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
fn visit_item(&mut self, item: &'tcx Item) {
let def_id = self.map.local_def_id_from_hir_id(item.hir_id);
let def_key = self.map.def_key(def_id);
let at_root = def_key.parent == Some(CRATE_DEF_INDEX);
find_item(item, self, at_root);
}
fn visit_trait_item(&mut self, _trait_item: &'tcx TraitItem) {
// entry fn is never a trait item
}
fn visit_impl_item(&mut self, _impl_item: &'tcx ImplItem) {
// entry fn is never an impl item
}
}
fn entry_fn(tcx: TyCtxt<'_, '_, '_>, cnum: CrateNum) -> Option<(DefId, EntryFnType)> {
assert_eq!(cnum, LOCAL_CRATE);
let any_exe = tcx.sess.crate_types.borrow().iter().any(|ty| {
*ty == config::CrateType::Executable
});
if !any_exe {
// No need to find a main function
return None;
}
// If the user wants no main function at all, then stop here.
if attr::contains_name(&tcx.hir().krate().attrs, "no_main") {
return None;
}
let mut ctxt = EntryContext {
session: tcx.sess,
map: tcx.hir(),
main_fn: None,
attr_main_fn: None,
start_fn: None,
non_main_fns: Vec::new(),
};
tcx.hir().krate().visit_all_item_likes(&mut ctxt);
configure_main(tcx, &ctxt)
}
// Beware, this is duplicated in `libsyntax/entry.rs`, so make sure to keep
// them in sync.
fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
match item.node {
ItemKind::Fn(..) => {
if attr::contains_name(&item.attrs, "start") {
EntryPointType::Start
} else if attr::contains_name(&item.attrs, "main") {
EntryPointType::MainAttr
} else if item.ident.name == "main" {
if at_root {
// This is a top-level function so can be 'main'.
EntryPointType::MainNamed
} else {
EntryPointType::OtherMain
}
} else {
EntryPointType::None
}
}
_ => EntryPointType::None,
}
}
fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
match entry_point_type(item, at_root) {
EntryPointType::MainNamed => {
if ctxt.main_fn.is_none() {
ctxt.main_fn = Some((item.hir_id, item.span));
} else {
span_err!(ctxt.session, item.span, E0136,
"multiple 'main' functions");
}
},
EntryPointType::OtherMain => {
ctxt.non_main_fns.push((item.hir_id, item.span));
},
EntryPointType::MainAttr => {
if ctxt.attr_main_fn.is_none() {
ctxt.attr_main_fn = Some((item.hir_id, item.span));
} else {
struct_span_err!(ctxt.session, item.span, E0137,
"multiple functions with a #[main] attribute")
.span_label(item.span, "additional #[main] function")
.span_label(ctxt.attr_main_fn.unwrap().1, "first #[main] function")
.emit();
}
},
EntryPointType::Start => {
if ctxt.start_fn.is_none() {
ctxt.start_fn = Some((item.hir_id, item.span));
} else {
struct_span_err!(ctxt.session, item.span, E0138, "multiple 'start' functions")
.span_label(ctxt.start_fn.unwrap().1, "previous `start` function here")
.span_label(item.span, "multiple `start` functions")
.emit();
}
}
EntryPointType::None => (),
}
}
fn configure_main(
tcx: TyCtxt<'_, '_, '_>,
visitor: &EntryContext<'_, '_>,
) -> Option<(DefId, EntryFnType)> {
if let Some((hir_id, _)) = visitor.start_fn {
Some((tcx.hir().local_def_id_from_hir_id(hir_id), EntryFnType::Start))
} else if let Some((hir_id, _)) = visitor.attr_main_fn {
Some((tcx.hir().local_def_id_from_hir_id(hir_id), EntryFnType::Main))
} else if let Some((hir_id, _)) = visitor.main_fn {
Some((tcx.hir().local_def_id_from_hir_id(hir_id), EntryFnType::Main))
} else {
// No main function
let mut err = struct_err!(tcx.sess, E0601,
"`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
if !visitor.non_main_fns.is_empty() {
// There were some functions named 'main' though. Try to give the user a hint.
err.note("the main function must be defined at the crate level \
but you have one or more functions named 'main' that are not \
defined at the crate level. Either move the definition or \
attach the `#[main]` attribute to override this behavior.");
for &(_, span) in &visitor.non_main_fns {
err.span_note(span, "here is a function named 'main'");
}
err.emit();
tcx.sess.abort_if_errors();
} else {
if let Some(ref filename) = tcx.sess.local_crate_source_file {
err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
}
if tcx.sess.teach(&err.get_code().unwrap()) {
err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
to get started: https://doc.rust-lang.org/book/");
}
err.emit();
}
None
}
}
pub fn find_entry_point(tcx: TyCtxt<'_, '_, '_>) -> Option<(DefId, EntryFnType)> {
tcx.entry_fn(LOCAL_CRATE)
}
pub fn provide(providers: &mut Providers<'_>) {
*providers = Providers {
entry_fn,
..*providers
};
}
|
