extend on_missing_args to no-match

Author: chenyukang

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -76,7 +76,7 @@ pub(super) fn failed_to_match_macro(
     let span = token.span.substitute_dummy(sp);
     let CustomDiagnostic {
         message: custom_message, label: custom_label, notes: custom_notes, ..
-    } = if matches!(token.kind, token::Eof) {
+    } = {
         let macro_name = name.to_string();
         on_missing_args
             .map(|directive| {
@@ -91,8 +91,6 @@ pub(super) fn failed_to_match_macro(
                 )
             })
             .unwrap_or_default()
-    } else {
-        CustomDiagnostic::default()
     };
 
     let mut err = match custom_message {

src/doc/unstable-book/src/language-features/diagnostic-on-missing-args.md

@@ -8,12 +8,12 @@ The tracking issue for this feature is: [#152494]
 
 The `diagnostic_on_missing_args` feature adds the
 `#[diagnostic::on_missing_args(...)]` attribute for declarative macros.
-It lets a macro definition customize the diagnostic that is emitted when an invocation ends before
-all required arguments were provided.
+It lets a macro definition customize diagnostics for matcher failures after all arms have been
+tried, such as incomplete invocations or trailing extra arguments.
 
 This attribute currently applies to declarative macros such as `macro_rules!` and `pub macro`.
-It only affects diagnostics for incomplete invocations; other matcher failures continue to use the
-usual macro diagnostics.
+It is currently used for errors emitted by declarative macro matching itself; fragment parser
+errors still use their existing diagnostics.
 
 ```rust,compile_fail
 #![feature(diagnostic_on_missing_args)]

tests/ui/diagnostic_namespace/on_missing_args/notes_on_extra_args.rs

@@ -0,0 +1,21 @@
+#![feature(diagnostic_on_missing_args)]
+
+#[diagnostic::on_missing_args(
+    message = "{This}! expects exactly two arguments",
+    label = "unexpected extra input starts here",
+    note = "this macro expects a type and a value, like `pair!(u8, 0)`",
+    note = "make sure to pass both arguments",
+)]
+macro_rules! pair {
+    //~^ NOTE when calling this macro
+    ($ty:ty, $value:expr) => {};
+    //~^ NOTE while trying to match meta-variable `$value:expr`
+}
+
+fn main() {
+    pair!(u8, 0, 42);
+    //~^ ERROR pair! expects exactly two arguments
+    //~| NOTE unexpected extra input starts here
+    //~| NOTE this macro expects a type and a value, like `pair!(u8, 0)`
+    //~| NOTE make sure to pass both arguments
+}

tests/ui/diagnostic_namespace/on_missing_args/notes_on_extra_args.stderr

@@ -0,0 +1,19 @@
+error: pair! expects exactly two arguments
+  --> $DIR/notes_on_extra_args.rs:16:16
+   |
+LL | macro_rules! pair {
+   | ----------------- when calling this macro
+...
+LL |     pair!(u8, 0, 42);
+   |                ^ unexpected extra input starts here
+   |
+note: while trying to match meta-variable `$value:expr`
+  --> $DIR/notes_on_extra_args.rs:11:14
+   |
+LL |     ($ty:ty, $value:expr) => {};
+   |              ^^^^^^^^^^^
+   = note: this macro expects a type and a value, like `pair!(u8, 0)`
+   = note: make sure to pass both arguments
+
+error: aborting due to 1 previous error
+

tests/ui/diagnostic_namespace/on_missing_args/other_match_macro_error.rs

@@ -0,0 +1,14 @@
+#![feature(diagnostic_on_missing_args)]
+
+#[diagnostic::on_missing_args(
+    message = "invalid route method",
+    note = "this macro expects a action, like `{This}!(get \"/hello\")`"
+)]
+macro_rules! route {
+    (get $path:literal) => {};
+}
+
+fn main() {
+    route!(post "/");
+    //~^ ERROR invalid route method
+}

tests/ui/diagnostic_namespace/on_missing_args/other_match_macro_error.stderr

@@ -0,0 +1,18 @@
+error: invalid route method
+  --> $DIR/other_match_macro_error.rs:12:12
+   |
+LL | macro_rules! route {
+   | ------------------ when calling this macro
+...
+LL |     route!(post "/");
+   |            ^^^^ no rules expected this token in macro call
+   |
+note: while trying to match `get`
+  --> $DIR/other_match_macro_error.rs:8:6
+   |
+LL |     (get $path:literal) => {};
+   |      ^^^
+   = note: this macro expects a action, like `route!(get "/hello")`
+
+error: aborting due to 1 previous error
+