Add justification to non-static lifetime diagnostic

dtolnay · dtolnay · commit d31d96bba247 · 2020-12-26T17:27:02.000-08:00
diff --git a/impl/src/valid.rs b/impl/src/valid.rs
@@ -191,7 +191,7 @@ fn check_field_attrs(fields: &[Field]) -> Result<()> {
         if contains_non_static_lifetime(source_field) {
             return Err(Error::new_spanned(
                 &source_field.original.ty,
-                "non-static lifetimes are not allowed in the source of an error",
+                "non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static",
             ));
         }
     }
diff --git a/tests/ui/lifetime.stderr b/tests/ui/lifetime.stderr
@@ -1,4 +1,4 @@
-error: non-static lifetimes are not allowed in the source of an error
+error: non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static
  --> $DIR/lifetime.rs:5:26
   |
 5 | struct Error<'a>(#[from] Inner<'a>);

Original file line number	Diff line number	Diff line change
`@@ -191,7 +191,7 @@ fn check_field_attrs(fields: &[Field]) -> Result<()> {`
`191`	`191`	`if contains_non_static_lifetime(source_field) {`
`192`	`192`	`return Err(Error::new_spanned(`
`193`	`193`	`&source_field.original.ty,`
`194`		`- "non-static lifetimes are not allowed in the source of an error",`
	`194`	`+ "non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static",`
`195`	`195`	`));`
`196`	`196`	`}`
`197`	`197`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-error: non-static lifetimes are not allowed in the source of an error`
	`1`	`+error: non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static`
`2`	`2`	`--> $DIR/lifetime.rs:5:26`
`3`	`3`	`\|`
`4`	`4`	`5 \| struct Error<'a>(#[from] Inner<'a>);`