For E0277 suggest adding Result
return type for function which using QuesionMark ?
in the body.
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@ -1010,6 +1010,7 @@ pub struct Block<'hir> {
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pub hir_id: HirId,
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/// Distinguishes between `unsafe { ... }` and `{ ... }`.
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pub rules: BlockCheckMode,
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/// The span includes the curly braces `{` and `}` around the block.
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pub span: Span,
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/// If true, then there may exist `break 'a` values that aim to
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/// break out of this block early.
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@ -4586,6 +4586,47 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
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_ => "/* value */".to_string(),
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})
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}
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fn suggest_add_result_as_return_type(
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&self,
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obligation: &PredicateObligation<'tcx>,
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err: &mut Diag<'_>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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) {
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if ObligationCauseCode::QuestionMark != *obligation.cause.code().peel_derives() {
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return;
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}
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let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
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if let hir::Node::Item(item) = node
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&& let hir::ItemKind::Fn(sig, _, body_id) = item.kind
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&& let hir::FnRetTy::DefaultReturn(ret_span) = sig.decl.output
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&& self.tcx.is_diagnostic_item(sym::FromResidual, trait_ref.def_id())
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&& let ty::Tuple(l) = trait_ref.skip_binder().args.type_at(0).kind()
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&& l.len() == 0
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&& let ty::Adt(def, _) = trait_ref.skip_binder().args.type_at(1).kind()
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&& self.tcx.is_diagnostic_item(sym::Result, def.did())
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{
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let body = self.tcx.hir().body(body_id);
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let mut sugg_spans =
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vec![(ret_span, " -> Result<(), Box<dyn std::error::Error>>".to_string())];
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if let hir::ExprKind::Block(b, _) = body.value.kind
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&& b.expr.is_none()
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{
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sugg_spans.push((
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// The span will point to the closing curly brace `}` of the block.
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b.span.shrink_to_hi().with_lo(b.span.hi() - BytePos(1)),
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"\n Ok(())\n}".to_string(),
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));
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}
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err.multipart_suggestion_verbose(
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format!("consider adding return type"),
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sugg_spans,
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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/// Add a hint to add a missing borrow or remove an unnecessary one.
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@ -612,6 +612,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
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&mut err,
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trait_predicate,
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);
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self.suggest_add_result_as_return_type(&obligation,
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&mut err,
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trait_ref);
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if self.suggest_add_reference_to_arg(
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&obligation,
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&mut err,
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42
tests/ui/return/return-from-residual-sugg-issue-125997.fixed
Normal file
42
tests/ui/return/return-from-residual-sugg-issue-125997.fixed
Normal file
@ -0,0 +1,42 @@
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//@ run-rustfix
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#![allow(unused_imports)]
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#![allow(dead_code)]
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use std::fs::File;
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use std::io::prelude::*;
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fn test1() -> Result<(), Box<dyn std::error::Error>> {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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Ok(())
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}
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fn test2() -> Result<(), Box<dyn std::error::Error>> {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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println!();
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Ok(())
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}
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macro_rules! mac {
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() => {
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fn test3() -> Result<(), Box<dyn std::error::Error>> {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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println!();
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Ok(())
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}
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};
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}
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fn main() -> Result<(), Box<dyn std::error::Error>> {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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mac!();
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Ok(())
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}
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34
tests/ui/return/return-from-residual-sugg-issue-125997.rs
Normal file
34
tests/ui/return/return-from-residual-sugg-issue-125997.rs
Normal file
@ -0,0 +1,34 @@
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//@ run-rustfix
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#![allow(unused_imports)]
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#![allow(dead_code)]
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use std::fs::File;
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use std::io::prelude::*;
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fn test1() {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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}
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fn test2() {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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println!();
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}
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macro_rules! mac {
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() => {
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fn test3() {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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println!();
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}
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};
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}
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fn main() {
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let mut _file = File::create("foo.txt")?;
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//~^ ERROR the `?` operator can only be used in a function
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mac!();
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}
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@ -0,0 +1,86 @@
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error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/return-from-residual-sugg-issue-125997.rs:10:44
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LL | fn test1() {
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| ---------- this function should return `Result` or `Option` to accept `?`
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test1() -> Result<(), Box<dyn std::error::Error>> {
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LL | let mut _file = File::create("foo.txt")?;
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LL |
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LL +
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LL + Ok(())
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LL + }
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error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/return-from-residual-sugg-issue-125997.rs:15:44
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LL | fn test2() {
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| ---------- this function should return `Result` or `Option` to accept `?`
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test2() -> Result<(), Box<dyn std::error::Error>> {
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LL | let mut _file = File::create("foo.txt")?;
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LL |
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LL | println!();
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LL +
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LL + Ok(())
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LL + }
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error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/return-from-residual-sugg-issue-125997.rs:31:44
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LL | fn main() {
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| --------- this function should return `Result` or `Option` to accept `?`
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
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LL | let mut _file = File::create("foo.txt")?;
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LL |
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LL | mac!();
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LL +
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LL + Ok(())
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LL + }
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error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/return-from-residual-sugg-issue-125997.rs:23:52
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LL | fn test3() {
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| ---------- this function should return `Result` or `Option` to accept `?`
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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...
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LL | mac!();
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| ------ in this macro invocation
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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= note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider adding return type
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LL ~ fn test3() -> Result<(), Box<dyn std::error::Error>> {
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LL | let mut _file = File::create("foo.txt")?;
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LL |
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LL | println!();
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LL ~
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LL + Ok(())
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LL + }
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0277`.
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@ -8,6 +8,16 @@ LL | std::fs::File::open("foo")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
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LL | // error for a `Try` type on a non-`Try` fn
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...
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LL | try_trait_generic::<()>();
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LL +
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LL + Ok(())
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LL + }
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error[E0277]: the `?` operator can only be applied to values that implement `Try`
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--> $DIR/try-operator-on-main.rs:10:5
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