/
need_type_info.rs
169 lines (153 loc) · 6.15 KB
/
need_type_info.rs
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// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
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::codemap::CompilerDesugaringKind;
use syntax_pos::Span;
use errors::DiagnosticBuilder;
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> {
pub 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_err(&self,
body_id: Option<hir::BodyId>,
span: Span,
ty: Ty<'tcx>)
-> DiagnosticBuilder<'gcx> {
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,
if &name == "_" {
"cannot infer type".to_string()
} else {
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;
// We don't want to show the default label for closures.
//
// So, before clearing, the output would look something like this:
// ```
// let x = |_| { };
// - ^^^^ cannot infer type for `[_; 0]`
// |
// consider giving this closure parameter a type
// ```
//
// After clearing, it looks something like this:
// ```
// let x = |_| { };
// ^ consider giving this closure parameter a type
// ```
labels.clear();
labels.push(
(pattern.span, "consider giving this closure parameter a type".to_string()));
} else if let Some(pattern) = local_visitor.found_local_pattern {
if let Some(simple_ident) = pattern.simple_ident() {
match pattern.span.compiler_desugaring_kind() {
None => labels.push((pattern.span,
format!("consider giving `{}` a type", simple_ident))),
Some(CompilerDesugaringKind::ForLoop) => labels.push((
pattern.span,
"the element type for this iterator is not specified".to_string(),
)),
_ => {}
}
} else {
labels.push((pattern.span, "consider giving the pattern a type".to_string()));
}
}
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
}
}