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use hir::{self, Local, Pat, Body, HirId};
use hir::intravisit::{self, Visitor, NestedVisitorMap};
use infer::InferCtxt;
use infer::type_variable::TypeVariableOrigin;
use ty::{self, Ty, TyInfer, TyVar};
use syntax_pos::Span;
struct FindLocalByTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
target_ty: &'a Ty<'tcx>,
hir_map: &'a hir::map::Map<'gcx>,
found_local_pattern: Option<&'gcx Pat>,
found_arg_pattern: Option<&'gcx Pat>,
}
impl<'a, 'gcx, 'tcx> FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
fn node_matches_type(&mut self, node_id: HirId) -> bool {
let ty_opt = self.infcx.in_progress_tables.and_then(|tables| {
tables.borrow().node_id_to_type_opt(node_id)
});
match ty_opt {
Some(ty) => {
let ty = self.infcx.resolve_type_vars_if_possible(&ty);
ty.walk().any(|inner_ty| {
inner_ty == *self.target_ty || match (&inner_ty.sty, &self.target_ty.sty) {
(&TyInfer(TyVar(a_vid)), &TyInfer(TyVar(b_vid))) => {
self.infcx
.type_variables
.borrow_mut()
.sub_unified(a_vid, b_vid)
}
_ => false,
}
})
}
None => false,
}
}
}
impl<'a, 'gcx, 'tcx> Visitor<'gcx> for FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
NestedVisitorMap::OnlyBodies(&self.hir_map)
}
fn visit_local(&mut self, local: &'gcx Local) {
if self.found_local_pattern.is_none() && self.node_matches_type(local.hir_id) {
self.found_local_pattern = Some(&*local.pat);
}
intravisit::walk_local(self, local);
}
fn visit_body(&mut self, body: &'gcx Body) {
for argument in &body.arguments {
if self.found_arg_pattern.is_none() && self.node_matches_type(argument.hir_id) {
self.found_arg_pattern = Some(&*argument.pat);
}
}
intravisit::walk_body(self, body);
}
}
impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
fn extract_type_name(&self, ty: &'a Ty<'tcx>) -> String {
if let ty::TyInfer(ty::TyVar(ty_vid)) = (*ty).sty {
let ty_vars = self.type_variables.borrow();
if let TypeVariableOrigin::TypeParameterDefinition(_, name) =
*ty_vars.var_origin(ty_vid) {
name.to_string()
} else {
ty.to_string()
}
} else {
ty.to_string()
}
}
pub fn need_type_info(&self, body_id: Option<hir::BodyId>, span: Span, ty: Ty<'tcx>) {
let ty = self.resolve_type_vars_if_possible(&ty);
let name = self.extract_type_name(&ty);
let mut err_span = span;
let mut labels = vec![(span, format!("cannot infer type for `{}`", name))];
let mut local_visitor = FindLocalByTypeVisitor {
infcx: &self,
target_ty: &ty,
hir_map: &self.tcx.hir,
found_local_pattern: None,
found_arg_pattern: None,
};
if let Some(body_id) = body_id {
let expr = self.tcx.hir.expect_expr(body_id.node_id);
local_visitor.visit_expr(expr);
}
if let Some(pattern) = local_visitor.found_arg_pattern {
err_span = pattern.span;
labels.clear();
labels.push((pattern.span, format!("consider giving this closure parameter a type")));
} else if let Some(pattern) = local_visitor.found_local_pattern {
if let Some(simple_name) = pattern.simple_name() {
labels.push((pattern.span, format!("consider giving `{}` a type", simple_name)));
} else {
labels.push((pattern.span, format!("consider giving the pattern a type")));
}
}
let mut err = struct_span_err!(self.tcx.sess,
err_span,
E0282,
"type annotations needed");
for (target_span, label_message) in labels {
err.span_label(target_span, label_message);
}
err.emit();
}
}