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Suggest calling associated fn inside traits
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When calling a function that doesn't exist inside of a trait's
associated `fn`, and another associated `fn` in that trait has that
name, suggest calling it with the appropriate fully-qualified path.

Expand the label to be more descriptive.

Prompted by the following user experience:
https://users.rust-lang.org/t/cannot-find-function/50663
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@estebank
estebank committed Oct 26, 2020
1 parent 9f6c670 commit 9e16213
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Showing 9 changed files with 124 additions and 49 deletions.
24 changes: 8 additions & 16 deletions compiler/rustc_resolve/src/late.rs
View file
Expand Up @@ -353,8 +353,8 @@ impl<'a> PathSource<'a> {

#[derive(Default)]
struct DiagnosticMetadata<'ast> {
/// The current trait's associated types' ident, used for diagnostic suggestions.
current_trait_assoc_types: Vec<Ident>,
/// The current trait's associated items' ident, used for diagnostic suggestions.
current_trait_assoc_items: Option<&'ast [P<AssocItem>]>,

/// The current self type if inside an impl (used for better errors).
current_self_type: Option<Ty>,
Expand Down Expand Up @@ -1148,26 +1148,18 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
result
}

/// When evaluating a `trait` use its associated types' idents for suggestionsa in E0412.
/// When evaluating a `trait` use its associated types' idents for suggestions in E0412.
fn with_trait_items<T>(
&mut self,
trait_items: &Vec<P<AssocItem>>,
trait_items: &'ast Vec<P<AssocItem>>,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let trait_assoc_types = replace(
&mut self.diagnostic_metadata.current_trait_assoc_types,
trait_items
.iter()
.filter_map(|item| match &item.kind {
AssocItemKind::TyAlias(_, _, bounds, _) if bounds.is_empty() => {
Some(item.ident)
}
_ => None,
})
.collect(),
let trait_assoc_items = replace(
&mut self.diagnostic_metadata.current_trait_assoc_items,
Some(&trait_items[..]),
);
let result = f(self);
self.diagnostic_metadata.current_trait_assoc_types = trait_assoc_types;
self.diagnostic_metadata.current_trait_assoc_items = trait_assoc_items;
result
}

Expand Down
58 changes: 47 additions & 11 deletions compiler/rustc_resolve/src/late/diagnostics.rs
View file
Expand Up @@ -30,7 +30,21 @@ type Res = def::Res<ast::NodeId>;
enum AssocSuggestion {
Field,
MethodWithSelf,
AssocItem,
AssocFn,
AssocType,
AssocConst,
}

impl AssocSuggestion {
fn action(&self) -> &'static str {
match self {
AssocSuggestion::Field => "use the available field",
AssocSuggestion::MethodWithSelf => "call the method with the fully-qualified path",
AssocSuggestion::AssocFn => "call the associated function",
AssocSuggestion::AssocConst => "use the associated `const`",
AssocSuggestion::AssocType => "use the associated type",
}
}
}

crate enum MissingLifetimeSpot<'tcx> {
Expand Down Expand Up @@ -386,15 +400,18 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
AssocSuggestion::MethodWithSelf if self_is_available => {
err.span_suggestion(
span,
"try",
"you might have meant to call the method",
format!("self.{}", path_str),
Applicability::MachineApplicable,
);
}
AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
AssocSuggestion::MethodWithSelf
| AssocSuggestion::AssocFn
| AssocSuggestion::AssocConst
| AssocSuggestion::AssocType => {
err.span_suggestion(
span,
"try",
&format!("you might have meant to {}", candidate.action()),
format!("Self::{}", path_str),
Applicability::MachineApplicable,
);
Expand Down Expand Up @@ -1048,9 +1065,19 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
}
}

for assoc_type_ident in &self.diagnostic_metadata.current_trait_assoc_types {
if *assoc_type_ident == ident {
return Some(AssocSuggestion::AssocItem);
if let Some(items) = self.diagnostic_metadata.current_trait_assoc_items {
for assoc_item in &items[..] {
if assoc_item.ident == ident {
return Some(match &assoc_item.kind {
ast::AssocItemKind::Const(..) => AssocSuggestion::AssocConst,
ast::AssocItemKind::Fn(_, sig, ..) if sig.decl.has_self() => {
AssocSuggestion::MethodWithSelf
}
ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn,
ast::AssocItemKind::TyAlias(..) => AssocSuggestion::AssocType,
ast::AssocItemKind::MacCall(_) => continue,
});
}
}
}

Expand All @@ -1066,11 +1093,20 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
) {
let res = binding.res();
if filter_fn(res) {
return Some(if self.r.has_self.contains(&res.def_id()) {
AssocSuggestion::MethodWithSelf
if self.r.has_self.contains(&res.def_id()) {
return Some(AssocSuggestion::MethodWithSelf);
} else {
AssocSuggestion::AssocItem
});
match res {
Res::Def(DefKind::AssocFn, _) => return Some(AssocSuggestion::AssocFn),
Res::Def(DefKind::AssocConst, _) => {
return Some(AssocSuggestion::AssocConst);
}
Res::Def(DefKind::AssocTy, _) => {
return Some(AssocSuggestion::AssocType);
}
_ => {}
}
}
}
}
}
Expand Down
32 changes: 32 additions & 0 deletions src/test/ui/resolve/associated-fn-called-as-fn.rs
View file
@@ -0,0 +1,32 @@
struct S;
impl Foo for S {
fn parse(s:&str) {
for c in s.chars() {
match c {
'0'..='9' => collect_primary(&c), //~ ERROR cannot find function `collect_primary`
//~^ HELP you might have meant to call the associated function
'+' | '-' => println!("We got a sign: {}", c),
_ => println!("Not a number!")
}
}
}
}
trait Foo {
fn collect_primary(ch:&char) { }
fn parse(s:&str);
}
trait Bar {
fn collect_primary(ch:&char) { }
fn parse(s:&str) {
for c in s.chars() {
match c {
'0'..='9' => collect_primary(&c), //~ ERROR cannot find function `collect_primary`
//~^ HELP you might have meant to call the associated function
'+' | '-' => println!("We got a sign: {}", c),
_ => println!("Not a number!")
}
}
}
}

fn main() {}
15 changes: 15 additions & 0 deletions src/test/ui/resolve/associated-fn-called-as-fn.stderr
View file
@@ -0,0 +1,15 @@
error[E0425]: cannot find function `collect_primary` in this scope
--> $DIR/associated-fn-called-as-fn.rs:6:30
|
LL | '0'..='9' => collect_primary(&c),
| ^^^^^^^^^^^^^^^ help: you might have meant to call the associated function: `Self::collect_primary`

error[E0425]: cannot find function `collect_primary` in this scope
--> $DIR/associated-fn-called-as-fn.rs:23:30
|
LL | '0'..='9' => collect_primary(&c),
| ^^^^^^^^^^^^^^^ help: you might have meant to call the associated function: `Self::collect_primary`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0425`.
30 changes: 15 additions & 15 deletions src/test/ui/resolve/issue-14254.stderr
View file
Expand Up @@ -2,7 +2,7 @@ error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:19:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `a` in this scope
--> $DIR/issue-14254.rs:21:9
Expand All @@ -14,7 +14,7 @@ error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:28:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-14254.rs:30:9
Expand All @@ -38,7 +38,7 @@ error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:36:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find value `b` in this scope
--> $DIR/issue-14254.rs:38:9
Expand All @@ -50,7 +50,7 @@ error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:45:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-14254.rs:47:9
Expand All @@ -74,7 +74,7 @@ error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:53:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find value `b` in this scope
--> $DIR/issue-14254.rs:55:9
Expand All @@ -86,61 +86,61 @@ error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:62:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:64:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:71:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:73:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:80:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:82:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:89:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:91:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error[E0425]: cannot find function `baz` in this scope
--> $DIR/issue-14254.rs:98:9
|
LL | baz();
| ^^^ help: try: `self.baz`
| ^^^ help: you might have meant to call the method: `self.baz`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/issue-14254.rs:100:9
|
LL | bah;
| ^^^ help: try: `Self::bah`
| ^^^ help: you might have meant to call the associated function: `Self::bah`

error: aborting due to 24 previous errors

Expand Down
6 changes: 3 additions & 3 deletions src/test/ui/resolve/issue-2356.stderr
View file
Expand Up @@ -8,15 +8,15 @@ error[E0425]: cannot find function `clone` in this scope
--> $DIR/issue-2356.rs:24:5
|
LL | clone();
| ^^^^^ help: try: `self.clone`
| ^^^^^ help: you might have meant to call the method: `self.clone`

error[E0425]: cannot find function `default` in this scope
--> $DIR/issue-2356.rs:31:5
|
LL | default();
| ^^^^^^^
|
help: try
help: you might have meant to call the associated function
|
LL | Self::default();
| ^^^^^^^^^^^^^
Expand All @@ -35,7 +35,7 @@ error[E0425]: cannot find function `shave` in this scope
--> $DIR/issue-2356.rs:41:5
|
LL | shave(4);
| ^^^^^ help: try: `Self::shave`
| ^^^^^ help: you might have meant to call the associated function: `Self::shave`

error[E0425]: cannot find function `purr` in this scope
--> $DIR/issue-2356.rs:43:5
Expand Down
4 changes: 2 additions & 2 deletions src/test/ui/resolve/resolve-assoc-suggestions.stderr
View file
Expand Up @@ -20,7 +20,7 @@ error[E0412]: cannot find type `Type` in this scope
--> $DIR/resolve-assoc-suggestions.rs:23:16
|
LL | let _: Type;
| ^^^^ help: try: `Self::Type`
| ^^^^ help: you might have meant to use the associated type: `Self::Type`

error[E0531]: cannot find tuple struct or tuple variant `Type` in this scope
--> $DIR/resolve-assoc-suggestions.rs:25:13
Expand Down Expand Up @@ -50,7 +50,7 @@ error[E0425]: cannot find value `method` in this scope
--> $DIR/resolve-assoc-suggestions.rs:34:9
|
LL | method;
| ^^^^^^ help: try: `self.method`
| ^^^^^^ help: you might have meant to call the method: `self.method`

error: aborting due to 9 previous errors

Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/resolve/resolve-speculative-adjustment.stderr
View file
Expand Up @@ -20,7 +20,7 @@ error[E0425]: cannot find function `method` in this scope
--> $DIR/resolve-speculative-adjustment.rs:25:9
|
LL | method();
| ^^^^^^ help: try: `self.method`
| ^^^^^^ help: you might have meant to call the method: `self.method`

error: aborting due to 4 previous errors

Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/suggestions/assoc-type-in-method-return.stderr
View file
Expand Up @@ -2,7 +2,7 @@ error[E0412]: cannot find type `Bla` in this scope
--> $DIR/assoc-type-in-method-return.rs:3:25
|
LL | fn to_bla(&self) -> Bla;
| ^^^ help: try: `Self::Bla`
| ^^^ help: you might have meant to use the associated type: `Self::Bla`

error: aborting due to previous error

Expand Down

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