Add implicit data generation and use it for location tracking

Cargo.toml

@@ -25,11 +25,14 @@ exclude = [
 features = [ "std", "backtraces", "futures", "guide" ]
 
 [features]
-default = ["std"]
+default = ["std", "rust_1_46"]
 
 # Implement the `std::error::Error` trait.
 std = []
 
+# Add support for `#[track_caller]`
+rust_1_46 = ["snafu-derive/rust_1_46"]
+
 # Makes the backtrace type live
 backtraces = ["std", "backtrace"]
 

compatibility-tests/compile-fail/tests/ui/attribute-misuse-opt-out-wrong-field.rs

@@ -22,4 +22,16 @@ mod backtrace {
     }
 }
 
+mod implicit {
+    use snafu::prelude::*;
+
+    #[derive(Debug, Snafu)]
+    enum EnumError {
+        AVariant {
+            #[snafu(implicit(false))]
+            not_location: u8,
+        },
+    }
+}
+
 fn main() {}

compatibility-tests/compile-fail/tests/ui/attribute-misuse-opt-out-wrong-field.stderr

@@ -9,3 +9,9 @@ error: `backtrace(false)` attribute is only valid on a field named "backtrace",
    |
 19 |             #[snafu(backtrace(false))]
    |                     ^^^^^^^^^^^^^^^^
+
+error: `implicit(false)` attribute is only valid on a field named "location", not on other fields
+  --> $DIR/attribute-misuse-opt-out-wrong-field.rs:31:21
+   |
+31 |             #[snafu(implicit(false))]
+   |                     ^^^^^^^^^^^^^^^

compatibility-tests/compile-fail/tests/ui/attribute-misuse.rs

@@ -7,6 +7,7 @@ mod enum_misuse {
     #[snafu(source(true))]
     #[snafu(backtrace)]
     #[snafu(context)]
+    #[snafu(implicit)]
     enum EnumError {
         AVariant,
     }
@@ -22,6 +23,7 @@ mod variant_misuse {
         #[snafu(source)]
         #[snafu(backtrace)]
         #[snafu(crate_root(XXXX))]
+        #[snafu(implicit)]
         AVariant,
     }
 }
@@ -56,6 +58,7 @@ mod struct_misuse {
     #[snafu(source(true))]
     #[snafu(backtrace)]
     #[snafu(context)]
+    #[snafu(implicit)]
     struct StructError(Box<UsableError>);
 }
 

compatibility-tests/compile-fail/tests/ui/attribute-misuse.stderr

@@ -28,86 +28,104 @@ error: `context` attribute is only valid on enum variants or structs with named
 9 |     #[snafu(context)]
   |             ^^^^^^^
 
+error: `implicit` attribute is only valid on enum variant or struct fields with a name, not on an enum
+  --> $DIR/attribute-misuse.rs:10:13
+   |
+10 |     #[snafu(implicit)]
+   |             ^^^^^^^^
+
 error: `source` attribute is only valid on enum variant or struct fields with a name, not on an enum variant
-  --> $DIR/attribute-misuse.rs:21:46
+  --> $DIR/attribute-misuse.rs:22:46
    |
-21 |         #[snafu(display("an error variant"), source(from(XXXX, Box::new)))]
+22 |         #[snafu(display("an error variant"), source(from(XXXX, Box::new)))]
    |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `source` attribute is only valid on enum variant or struct fields with a name, not on an enum variant
-  --> $DIR/attribute-misuse.rs:22:17
+  --> $DIR/attribute-misuse.rs:23:17
    |
-22 |         #[snafu(source)]
+23 |         #[snafu(source)]
    |                 ^^^^^^
 
 error: `backtrace` attribute is only valid on enum variant or struct fields with a name, not on an enum variant
-  --> $DIR/attribute-misuse.rs:23:17
+  --> $DIR/attribute-misuse.rs:24:17
    |
-23 |         #[snafu(backtrace)]
+24 |         #[snafu(backtrace)]
    |                 ^^^^^^^^^
 
 error: `crate_root` attribute is only valid on an enum or a struct, not on an enum variant
-  --> $DIR/attribute-misuse.rs:24:17
+  --> $DIR/attribute-misuse.rs:25:17
    |
-24 |         #[snafu(crate_root(XXXX))]
+25 |         #[snafu(crate_root(XXXX))]
    |                 ^^^^^^^^^^^^^^^^
 
+error: `implicit` attribute is only valid on enum variant or struct fields with a name, not on an enum variant
+  --> $DIR/attribute-misuse.rs:26:17
+   |
+26 |         #[snafu(implicit)]
+   |                 ^^^^^^^^
+
 error: `display` attribute is only valid on enum variants or structs with named fields, not on a field
-  --> $DIR/attribute-misuse.rs:35:21
+  --> $DIR/attribute-misuse.rs:37:21
    |
-35 |             #[snafu(display("display should not work here"))]
+37 |             #[snafu(display("display should not work here"))]
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `visibility` attribute is only valid on an enum, enum variants, or a struct with named fields, not on a field
-  --> $DIR/attribute-misuse.rs:36:21
+  --> $DIR/attribute-misuse.rs:38:21
    |
-36 |             #[snafu(visibility(pub))]
+38 |             #[snafu(visibility(pub))]
    |                     ^^^^^^^^^^^^^^^
 
 error: Incompatible attributes [`source(false)`, `source(from)`] specified on a field
-  --> $DIR/attribute-misuse.rs:38:21
+  --> $DIR/attribute-misuse.rs:40:21
    |
-38 |             #[snafu(source(from(XXXX, Box::new)))]
+40 |             #[snafu(source(from(XXXX, Box::new)))]
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `context` attribute is only valid on enum variants or structs with named fields, not on a field
-  --> $DIR/attribute-misuse.rs:39:21
+  --> $DIR/attribute-misuse.rs:41:21
    |
-39 |             #[snafu(context)]
+41 |             #[snafu(context)]
    |                     ^^^^^^^
 
 error: `crate_root` attribute is only valid on an enum or a struct, not on a field
-  --> $DIR/attribute-misuse.rs:40:21
+  --> $DIR/attribute-misuse.rs:42:21
    |
-40 |             #[snafu(crate_root(XXXX))]
+42 |             #[snafu(crate_root(XXXX))]
    |                     ^^^^^^^^^^^^^^^^
 
 error: `display` attribute is only valid on enum variants or structs with named fields, not on a tuple struct
-  --> $DIR/attribute-misuse.rs:53:13
+  --> $DIR/attribute-misuse.rs:55:13
    |
-53 |     #[snafu(display("display should not work here"))]
+55 |     #[snafu(display("display should not work here"))]
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: `visibility` attribute is only valid on an enum, enum variants, or a struct with named fields, not on a tuple struct
-  --> $DIR/attribute-misuse.rs:55:13
+  --> $DIR/attribute-misuse.rs:57:13
    |
-55 |     #[snafu(visibility(pub))]
+57 |     #[snafu(visibility(pub))]
    |             ^^^^^^^^^^^^^^^
 
 error: `source(bool)` attribute is only valid on enum variant or struct fields with a name, not on a tuple struct
-  --> $DIR/attribute-misuse.rs:56:13
+  --> $DIR/attribute-misuse.rs:58:13
    |
-56 |     #[snafu(source(true))]
+58 |     #[snafu(source(true))]
    |             ^^^^^^^^^^^^
 
 error: `backtrace` attribute is only valid on enum variant or struct fields with a name, not on a tuple struct
-  --> $DIR/attribute-misuse.rs:57:13
+  --> $DIR/attribute-misuse.rs:59:13
    |
-57 |     #[snafu(backtrace)]
+59 |     #[snafu(backtrace)]
    |             ^^^^^^^^^
 
 error: `context` attribute is only valid on enum variants or structs with named fields, not on a tuple struct
-  --> $DIR/attribute-misuse.rs:58:13
+  --> $DIR/attribute-misuse.rs:60:13
    |
-58 |     #[snafu(context)]
+60 |     #[snafu(context)]
    |             ^^^^^^^
+
+error: `implicit` attribute is only valid on enum variant or struct fields with a name, not on a tuple struct
+  --> $DIR/attribute-misuse.rs:61:13
+   |
+61 |     #[snafu(implicit)]
+   |             ^^^^^^^^

compatibility-tests/compile-fail/tests/ui/duplication-implicit-attributes.rs

@@ -0,0 +1,22 @@
+use snafu::prelude::*;
+
+#[derive(Debug)]
+struct ImplicitData;
+
+impl snafu::GenerateImplicitData for ImplicitData {
+    fn generate() -> Self {
+        Self
+    }
+}
+
+#[derive(Debug, Snafu)]
+enum EnumError {
+    AVariant {
+        // Second attribute should be marked as duplicate
+        #[snafu(implicit)]
+        #[snafu(implicit)]
+        my_data: ImplicitData,
+    },
+}
+
+fn main() {}

compatibility-tests/compile-fail/tests/ui/duplication-implicit-attributes.stderr

@@ -0,0 +1,5 @@
+error: Multiple `implicit` attributes are not supported on a field
+  --> $DIR/duplication-implicit-attributes.rs:17:17
+   |
+17 |         #[snafu(implicit)]
+   |                 ^^^^^^^^

compatibility-tests/compile-fail/tests/ui/structs/attribute-misuse.stderr

@@ -1,4 +1,4 @@
-error: expected one of: `backtrace`, `context`, `crate_root`, `display`, `source`, `visibility`, `whatever`
+error: expected one of: `backtrace`, `context`, `crate_root`, `display`, `implicit`, `source`, `visibility`, `whatever`
  --> $DIR/attribute-misuse.rs:5:13
   |
 5 |     #[snafu(unknown_attribute)]

compatibility-tests/futures/src/lib.rs

@@ -1,5 +1,7 @@
 #![cfg(test)]
 
+mod location;
+
 mod api {
     use futures::{stream, StreamExt, TryStream};
     use snafu::prelude::*;