For E0277 suggest adding `Result` return type for function which using QuesionMark `?` in the body.

4 files changed, 172 insertions, 0 deletions

diff --git a/tests/ui/return/return-from-residual-sugg-issue-125997.fixed b/tests/ui/return/return-from-residual-sugg-issue-125997.fixed
new file mode 100644
index 00000000000..b2eca69aeb9
--- /dev/null
+++ b/tests/ui/return/return-from-residual-sugg-issue-125997.fixed
@@ -0,0 +1,42 @@
+//@ run-rustfix
+
+#![allow(unused_imports)]
+#![allow(dead_code)]
+
+use std::fs::File;
+use std::io::prelude::*;
+
+fn test1() -> Result<(), Box<dyn std::error::Error>> {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+
+    Ok(())
+}
+
+fn test2() -> Result<(), Box<dyn std::error::Error>> {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+    println!();
+
+    Ok(())
+}
+
+macro_rules! mac {
+    () => {
+        fn test3() -> Result<(), Box<dyn std::error::Error>> {
+            let mut _file = File::create("foo.txt")?;
+            //~^ ERROR the `?` operator can only be used in a function
+            println!();
+        
+    Ok(())
+}
+    };
+}
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+    mac!();
+
+    Ok(())
+}
diff --git a/tests/ui/return/return-from-residual-sugg-issue-125997.rs b/tests/ui/return/return-from-residual-sugg-issue-125997.rs
new file mode 100644
index 00000000000..dd8550a388b
--- /dev/null
+++ b/tests/ui/return/return-from-residual-sugg-issue-125997.rs
@@ -0,0 +1,34 @@
+//@ run-rustfix
+
+#![allow(unused_imports)]
+#![allow(dead_code)]
+
+use std::fs::File;
+use std::io::prelude::*;
+
+fn test1() {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+}
+
+fn test2() {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+    println!();
+}
+
+macro_rules! mac {
+    () => {
+        fn test3() {
+            let mut _file = File::create("foo.txt")?;
+            //~^ ERROR the `?` operator can only be used in a function
+            println!();
+        }
+    };
+}
+
+fn main() {
+    let mut _file = File::create("foo.txt")?;
+    //~^ ERROR the `?` operator can only be used in a function
+    mac!();
+}
diff --git a/tests/ui/return/return-from-residual-sugg-issue-125997.stderr b/tests/ui/return/return-from-residual-sugg-issue-125997.stderr
new file mode 100644
index 00000000000..ef938f0213d
--- /dev/null
+++ b/tests/ui/return/return-from-residual-sugg-issue-125997.stderr
@@ -0,0 +1,86 @@
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
+  --> $DIR/return-from-residual-sugg-issue-125997.rs:10:44
+   |
+LL | fn test1() {
+   | ---------- this function should return `Result` or `Option` to accept `?`
+LL |     let mut _file = File::create("foo.txt")?;
+   |                                            ^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
+help: consider adding return type
+   |
+LL ~ fn test1() -> Result<(), Box<dyn std::error::Error>> {
+LL |     let mut _file = File::create("foo.txt")?;
+LL |
+LL + 
+LL +     Ok(())
+LL + }
+   |
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
+  --> $DIR/return-from-residual-sugg-issue-125997.rs:15:44
+   |
+LL | fn test2() {
+   | ---------- this function should return `Result` or `Option` to accept `?`
+LL |     let mut _file = File::create("foo.txt")?;
+   |                                            ^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
+help: consider adding return type
+   |
+LL ~ fn test2() -> Result<(), Box<dyn std::error::Error>> {
+LL |     let mut _file = File::create("foo.txt")?;
+LL |
+LL |     println!();
+LL + 
+LL +     Ok(())
+LL + }
+   |
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
+  --> $DIR/return-from-residual-sugg-issue-125997.rs:31:44
+   |
+LL | fn main() {
+   | --------- this function should return `Result` or `Option` to accept `?`
+LL |     let mut _file = File::create("foo.txt")?;
+   |                                            ^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
+help: consider adding return type
+   |
+LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
+LL |     let mut _file = File::create("foo.txt")?;
+LL |
+LL |     mac!();
+LL + 
+LL +     Ok(())
+LL + }
+   |
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
+  --> $DIR/return-from-residual-sugg-issue-125997.rs:23:52
+   |
+LL |         fn test3() {
+   |         ---------- this function should return `Result` or `Option` to accept `?`
+LL |             let mut _file = File::create("foo.txt")?;
+   |                                                    ^ cannot use the `?` operator in a function that returns `()`
+...
+LL |     mac!();
+   |     ------ in this macro invocation
+   |
+   = help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
+   = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider adding return type
+   |
+LL ~         fn test3() -> Result<(), Box<dyn std::error::Error>> {
+LL |             let mut _file = File::create("foo.txt")?;
+LL |
+LL |             println!();
+LL ~         
+LL +     Ok(())
+LL + }
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/try-trait/try-operator-on-main.stderr b/tests/ui/try-trait/try-operator-on-main.stderr
index 7cd38e0cf95..ba6eacde68f 100644
--- a/tests/ui/try-trait/try-operator-on-main.stderr
+++ b/tests/ui/try-trait/try-operator-on-main.stderr
@@ -8,6 +8,16 @@ LL |     std::fs::File::open("foo")?;
    |                               ^ cannot use the `?` operator in a function that returns `()`
    |
    = help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
+help: consider adding return type
+   |
+LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
+LL |     // error for a `Try` type on a non-`Try` fn
+ ...
+LL |     try_trait_generic::<()>();
+LL + 
+LL +     Ok(())
+LL + }
+   |
 
 error[E0277]: the `?` operator can only be applied to values that implement `Try`
   --> $DIR/try-operator-on-main.rs:10:5