Merge pull request #116 from dtolnay/lifetime

Detect non-static lifetime behind reference type parameter

impl/src/valid.rs

@@ -188,7 +188,7 @@ fn check_field_attrs(fields: &[Field]) -> Result<()> {
         }
     }
     if let Some(source_field) = source_field.or(from_field) {
-        if contains_non_static_lifetime(source_field) {
+        if contains_non_static_lifetime(&source_field.ty) {
             return Err(Error::new_spanned(
                 &source_field.original.ty,
                 "non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static",
@@ -206,21 +206,28 @@ fn same_member(one: &Field, two: &Field) -> bool {
     }
 }
 
-fn contains_non_static_lifetime(field: &Field) -> bool {
-    let ty = match field.ty {
-        Type::Path(ty) => ty,
-        _ => return false, // maybe implement later if there are common other cases
-    };
-    let bracketed = match &ty.path.segments.last().unwrap().arguments {
-        PathArguments::AngleBracketed(bracketed) => bracketed,
-        _ => return false,
-    };
-    for arg in &bracketed.args {
-        if let GenericArgument::Lifetime(lifetime) = arg {
-            if lifetime.ident != "static" {
-                return true;
+fn contains_non_static_lifetime(ty: &Type) -> bool {
+    match ty {
+        Type::Path(ty) => {
+            let bracketed = match &ty.path.segments.last().unwrap().arguments {
+                PathArguments::AngleBracketed(bracketed) => bracketed,
+                _ => return false,
+            };
+            for arg in &bracketed.args {
+                match arg {
+                    GenericArgument::Type(ty) if contains_non_static_lifetime(ty) => return true,
+                    GenericArgument::Lifetime(lifetime) if lifetime.ident != "static" => {
+                        return true
+                    }
+                    _ => {}
+                }
             }
+            false
         }
+        Type::Reference(ty) => ty
+            .lifetime
+            .as_ref()
+            .map_or(false, |lifetime| lifetime.ident != "static"),
+        _ => false, // maybe implement later if there are common other cases
     }
-    false
 }

tests/ui/lifetime.rs

@@ -1,3 +1,4 @@
+use std::fmt::Debug;
 use thiserror::Error;
 
 #[derive(Error, Debug)]
@@ -8,6 +9,16 @@ struct Error<'a>(#[from] Inner<'a>);
 #[error("{0}")]
 struct Inner<'a>(&'a str);
 
+#[derive(Error, Debug)]
+enum Enum<'a> {
+    #[error("error")]
+    Foo(#[from] Generic<&'a str>),
+}
+
+#[derive(Error, Debug)]
+#[error("{0:?}")]
+struct Generic<T: Debug>(T);
+
 fn main() -> Result<(), Error<'static>> {
     Err(Error(Inner("some text")))
 }

tests/ui/lifetime.stderr

@@ -1,5 +1,11 @@
 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
+ --> $DIR/lifetime.rs:6:26
   |
-5 | struct Error<'a>(#[from] Inner<'a>);
+6 | struct Error<'a>(#[from] Inner<'a>);
   |                          ^^^^^^^^^
+
+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:15:17
+   |
+15 |     Foo(#[from] Generic<&'a str>),
+   |                 ^^^^^^^^^^^^^^^^