Auto merge of #139938 - matthiaskrgr:rollup-19ddpus, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #139084 (hygiene: Rename semi-transparent to semi-opaque)
 - #139236 (Use a session counter to make anon dep nodes unique)
 - #139650 (Fix `register_group_alias` for tools)
 - #139770 (Rename `LifetimeName` as `LifetimeKind`.)
 - #139846 (Remove `kw::Empty` uses in rustdoc)
 - #139891 (Include optional dso_local marker for functions in `enum-match.rs`)
 - #139908 (parser: Remove old diagnostic notes for type ascription syntax)
 - #139917 (fix for multiple `#[repr(align(N))]` on functions)

Failed merges:

 - #139615 (Remove `name_or_empty`)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 5 insertions, 2 deletions

diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 9d8eb70fbe0..5d85a4676b7 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -11,7 +11,7 @@ use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefId;
 use rustc_metadata::rendered_const;
 use rustc_middle::{bug, ty};
-use rustc_span::{Pos, Symbol};
+use rustc_span::{Pos, Symbol, kw};
 use rustdoc_json_types::*;
 
 use crate::clean::{self, ItemId};
@@ -611,7 +611,10 @@ impl FromClean<clean::FnDecl> for FunctionSignature {
             inputs: inputs
                 .values
                 .into_iter()
-                .map(|arg| (arg.name.to_string(), arg.type_.into_json(renderer)))
+                // `_` is the most sensible name for missing param names.
+                .map(|arg| {
+                    (arg.name.unwrap_or(kw::Underscore).to_string(), arg.type_.into_json(renderer))
+                })
                 .collect(),
             output: if output.is_unit() { None } else { Some(output.into_json(renderer)) },
             is_c_variadic: c_variadic,