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Tweak output

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- Only point at a the single expression where the found type was first
  inferred.
- Find method call argument that might have caused the found type to be
  inferred.
- Provide structured suggestion.
- Apply some review comments.
- Tweak wording.
This commit is contained in:
Esteban Küber 2023-01-03 20:20:31 -08:00
parent 6b0cce4b50
commit 9cc8d86190
7 changed files with 243 additions and 60 deletions
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167
compiler/rustc_hir_typeck/src/demand.rs
View File

@ -1,5 +1,6 @@
use crate::FnCtxt;
use rustc_ast::util::parser::PREC_POSTFIX;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::MultiSpan;
use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
use rustc_hir as hir;
@ -14,12 +15,14 @@ use rustc_middle::ty::adjustment::AllowTwoPhase;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::TypeFolder;
use rustc_middle::ty::print::{with_forced_trimmed_paths, with_no_trimmed_paths};
use rustc_middle::ty::relate::TypeRelation;
use rustc_middle::ty::{
self, Article, AssocItem, Ty, TyCtxt, TypeAndMut, TypeSuperFoldable, TypeVisitable,
};
use rustc_span::symbol::{sym, Symbol};
use rustc_span::{BytePos, Span};
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::traits::error_reporting::method_chain::CollectAllMismatches;
use rustc_trait_selection::traits::ObligationCause;
use super::method::probe;
@ -44,7 +47,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
self.annotate_alternative_method_deref(err, expr, error);
// Use `||` to give these suggestions a precedence
let _ = self.suggest_missing_parentheses(err, expr)
let suggested = self.suggest_missing_parentheses(err, expr)
|| self.suggest_remove_last_method_call(err, expr, expected)
|| self.suggest_associated_const(err, expr, expected)
|| self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
@ -57,8 +60,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
|| self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
|| self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
|| self.suggest_into(err, expr, expr_ty, expected)
|| self.suggest_floating_point_literal(err, expr, expected)
|| self.point_inference_types(err, expr);
|| self.suggest_floating_point_literal(err, expr, expected);
if !suggested {
self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
}
}
pub fn emit_coerce_suggestions(
@ -210,7 +215,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
(expected, Some(err))
}
fn point_inference_types(&self, err: &mut Diagnostic, expr: &hir::Expr<'_>) -> bool {
fn point_at_expr_source_of_inferred_type(
&self,
err: &mut Diagnostic,
expr: &hir::Expr<'_>,
found: Ty<'tcx>,
expected: Ty<'tcx>,
) -> bool {
let tcx = self.tcx;
let map = self.tcx.hir();
@ -250,25 +261,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
let hir::def::Res::Local(hir_id) = p.res else { return false; };
let Some(node) = map.find(hir_id) else { return false; };
let hir::Node::Pat(pat) = node else { return false; };
let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
let parent = map.get_parent_node(pat.hir_id);
let Some(hir::Node::Local(hir::Local {
ty: None,
init: Some(init),
..
})) = map.find(parent) else { return false; };
let ty = self.node_ty(init.hir_id);
let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
return false;
}
let mut span_labels = vec![(
init.span,
with_forced_trimmed_paths!(format!(
"here the type of `{ident}` is inferred to be `{ty}`",
)),
)];
// Locate all the usages of the relevant binding.
struct FindExprs<'hir> {
@ -296,71 +299,139 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
expr_finder.visit_expr(body.value);
let mut eraser = TypeEraser { tcx };
let mut prev = eraser.fold_ty(ty);
let mut prev_span = None;
for ex in expr_finder.uses {
if ex.span.overlaps(expr.span) { break; }
let parent = map.get_parent_node(ex.hir_id);
for binding in expr_finder.uses {
// In every expression where the binding is referenced, we will look at that
// expression's type and see if it is where the incorrect found type was fully
// "materialized" and point at it. We will also try to provide a suggestion there.
let parent = map.get_parent_node(binding.hir_id);
if let Some(hir::Node::Expr(expr))
| Some(hir::Node::Stmt(hir::Stmt {
kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
..
})) = &map.find(parent)
&& let hir::ExprKind::MethodCall(s, rcvr, args, span) = expr.kind
&& rcvr.hir_id == ex.hir_id
&& let hir::ExprKind::MethodCall(s, rcvr, args, _span) = expr.kind
&& rcvr.hir_id == binding.hir_id
&& let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
{
let ty = if let Ok(m) = self.lookup_method(ty, s, span, expr, rcvr, args) {
// We get the self type from `lookup_method` because the `rcvr` node
// type will not have had any adjustments from the fn arguments.
let ty = m.sig.inputs_and_output[0];
match ty.kind() {
// Remove one layer of references to account for `&mut self` and
// `&self`, so that we can compare it against the binding.
ty::Ref(_, ty, _) => *ty,
_ => ty,
}
} else {
self.node_ty(rcvr.hir_id)
// We special case methods, because they can influence inference through the
// call's arguments and we can provide a more explicit span.
let sig = self.tcx.fn_sig(def_id);
let def_self_ty = sig.input(0).skip_binder();
let rcvr_ty = self.node_ty(rcvr.hir_id);
// Get the evaluated type *after* calling the method call, so that the influence
// of the arguments can be reflected in the receiver type. The receiver
// expression has the type *before* theis analysis is done.
let ty = match self.lookup_probe(s.ident, rcvr_ty, expr, probe::ProbeScope::TraitsInScope) {
Ok(pick) => pick.self_ty,
Err(_) => rcvr_ty,
};
// Remove one layer of references to account for `&mut self` and
// `&self`, so that we can compare it against the binding.
let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
(ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
_ => (ty, def_self_ty),
};
let mut param_args = FxHashMap::default();
let mut param_expected = FxHashMap::default();
let mut param_found = FxHashMap::default();
if self.can_eq(self.param_env, ty, found).is_ok() {
// We only point at the first place where the found type was inferred.
for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
// We found an argument that references a type parameter in `Self`,
// so we assume that this is the argument that caused the found
// type, which we know already because of `can_eq` above was first
// inferred in this method call.
let arg = &args[i];
let arg_ty = self.node_ty(arg.hir_id);
err.span_label(
arg.span,
&format!(
"this is of type `{arg_ty}`, which makes `{ident}` to be \
inferred as `{ty}`",
),
);
param_args.insert(param_ty, (arg, arg_ty));
}
}
}
// Here we find, for a type param `T`, the type that `T` is in the current
// method call *and* in the original expected type. That way, we can see if we
// can give any structured suggestion for the function argument.
let mut c = CollectAllMismatches {
infcx: &self.infcx,
param_env: self.param_env,
errors: vec![],
};
let _ = c.relate(def_self_ty, ty);
for error in c.errors {
if let TypeError::Sorts(error) = error {
param_found.insert(error.expected, error.found);
}
}
c.errors = vec![];
let _ = c.relate(def_self_ty, expected);
for error in c.errors {
if let TypeError::Sorts(error) = error {
param_expected.insert(error.expected, error.found);
}
}
for (param, (arg,arg_ty)) in param_args.iter() {
let Some(expected) = param_expected.get(param) else { continue; };
let Some(found) = param_found.get(param) else { continue; };
if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
self.suggest_deref_ref_or_into(err, arg, *expected, *found, None);
}
let ty = eraser.fold_ty(ty);
if ty.references_error() {
break;
}
if ty != prev {
span_labels.push((
if ty != prev
&& param_args.is_empty()
&& self.can_eq(self.param_env, ty, found).is_ok()
{
// We only point at the first place where the found type was inferred.
err.span_label(
s.ident.span,
with_forced_trimmed_paths!(format!(
"here the type of `{ident}` is inferred to be `{ty}`",
)),
));
prev = ty;
);
break;
}
prev = ty;
} else {
let ty = eraser.fold_ty(self.node_ty(ex.hir_id));
let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
if ty.references_error() {
break;
}
if ty != prev {
span_labels.push((
ex.span,
if ty != prev && let Some(span) = prev_span && self.can_eq(self.param_env, ty, found).is_ok() {
// We only point at the first place where the found type was inferred.
// We use the *previous* span because if the type is known *here* it means
// it was *evaluated earlier*. We don't do this for method calls because we
// evaluate the method's self type eagerly, but not in any other case.
err.span_label(
span,
with_forced_trimmed_paths!(format!(
"here the type of `{ident}` is inferred to be `{ty}`",
)),
));
);
break;
}
prev = ty;
}
if ex.hir_id == expr.hir_id {
// Stop showing spans after the error type was emitted.
if binding.hir_id == expr.hir_id {
// Do not look at expressions that come after the expression we were originally
// evaluating and had a type error.
break;
}
prev_span = Some(binding.span);
}
}
if span_labels.len() < 2 {
return false;
}
for (sp, label) in span_labels {
err.span_label(sp, &label);
}
true
}

15
src/test/ui/type/type-check/assignment-in-if.stderr
View File

@ -67,10 +67,7 @@ LL | x == 5
error[E0308]: mismatched types
--> $DIR/assignment-in-if.rs:44:18
|
LL | let x = 1;
| - here the type of `x` is inferred to be `{integer}`
...
LL | println!("{}", x);
LL | if y = (Foo { foo: x }) {
| - here the type of `x` is inferred to be `usize`
...
LL | if x == x && x = x && x == x {
@ -81,10 +78,7 @@ LL | if x == x && x = x && x == x {
error[E0308]: mismatched types
--> $DIR/assignment-in-if.rs:44:22
|
LL | let x = 1;
| - here the type of `x` is inferred to be `{integer}`
...
LL | println!("{}", x);
LL | if y = (Foo { foo: x }) {
| - here the type of `x` is inferred to be `usize`
...
LL | if x == x && x = x && x == x {
@ -104,10 +98,7 @@ LL | if x == x && x == x && x == x {
error[E0308]: mismatched types
--> $DIR/assignment-in-if.rs:51:28
|
LL | let x = 1;
| - here the type of `x` is inferred to be `{integer}`
...
LL | println!("{}", x);
LL | if y = (Foo { foo: x }) {
| - here the type of `x` is inferred to be `usize`
...
LL | if x == x && x == x && x = x {

13
src/test/ui/type/type-check/point-at-inference-2.rs Normal file
View File

@ -0,0 +1,13 @@
fn bar(_: Vec<i32>) {}
fn baz(_: &Vec<&i32>) {}
fn main() {
let v = vec![&1];
bar(v); //~ ERROR E0308
let v = vec![];
baz(&v);
baz(&v);
bar(v); //~ ERROR E0308
let v = vec![];
baz(&v);
bar(v); //~ ERROR E0308
}

56
src/test/ui/type/type-check/point-at-inference-2.stderr Normal file
View File

@ -0,0 +1,56 @@
error[E0308]: mismatched types
--> $DIR/point-at-inference-2.rs:5:9
|
LL | bar(v);
| --- ^ expected `i32`, found `&{integer}`
| |
| arguments to this function are incorrect
|
= note: expected struct `Vec<i32>`
found struct `Vec<&{integer}>`
note: function defined here
--> $DIR/point-at-inference-2.rs:1:4
|
LL | fn bar(_: Vec<i32>) {}
| ^^^ -----------
error[E0308]: mismatched types
--> $DIR/point-at-inference-2.rs:9:9
|
LL | baz(&v);
| - here the type of `v` is inferred to be `Vec<&i32>`
LL | baz(&v);
LL | bar(v);
| --- ^ expected `i32`, found `&i32`
| |
| arguments to this function are incorrect
|
= note: expected struct `Vec<i32>`
found struct `Vec<&i32>`
note: function defined here
--> $DIR/point-at-inference-2.rs:1:4
|
LL | fn bar(_: Vec<i32>) {}
| ^^^ -----------
error[E0308]: mismatched types
--> $DIR/point-at-inference-2.rs:12:9
|
LL | baz(&v);
| - here the type of `v` is inferred to be `Vec<&i32>`
LL | bar(v);
| --- ^ expected `i32`, found `&i32`
| |
| arguments to this function are incorrect
|
= note: expected struct `Vec<i32>`
found struct `Vec<&i32>`
note: function defined here
--> $DIR/point-at-inference-2.rs:1:4
|
LL | fn bar(_: Vec<i32>) {}
| ^^^ -----------
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0308`.

13
src/test/ui/type/type-check/point-at-inference.fixed Normal file
View File

@ -0,0 +1,13 @@
// run-rustfix
fn bar(_: Vec<i32>) {}
fn baz(_: &impl std::any::Any) {}
fn main() {
let v = vec![1, 2, 3, 4, 5];
let mut foo = vec![];
baz(&foo);
for i in &v {
foo.push(*i);
}
baz(&foo);
bar(foo); //~ ERROR E0308
}

13
src/test/ui/type/type-check/point-at-inference.rs Normal file
View File

@ -0,0 +1,13 @@
// run-rustfix
fn bar(_: Vec<i32>) {}
fn baz(_: &impl std::any::Any) {}
fn main() {
let v = vec![1, 2, 3, 4, 5];
let mut foo = vec![];
baz(&foo);
for i in &v {
foo.push(i);
}
baz(&foo);
bar(foo); //~ ERROR E0308
}

26
src/test/ui/type/type-check/point-at-inference.stderr Normal file
View File

@ -0,0 +1,26 @@
error[E0308]: mismatched types
--> $DIR/point-at-inference.rs:12:9
|
LL | foo.push(i);
| - this is of type `&{integer}`, which makes `foo` to be inferred as `Vec<&{integer}>`
...
LL | bar(foo);
| --- ^^^ expected `i32`, found `&{integer}`
| |
| arguments to this function are incorrect
|
= note: expected struct `Vec<i32>`
found struct `Vec<&{integer}>`
note: function defined here
--> $DIR/point-at-inference.rs:2:4
|
LL | fn bar(_: Vec<i32>) {}
| ^^^ -----------
help: consider dereferencing the borrow
|
LL | foo.push(*i);
| +
error: aborting due to previous error
For more information about this error, try `rustc --explain E0308`.