diff --git a/Cargo.lock b/Cargo.lock
index c19e847164..7d03300c22 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1259,7 +1259,7 @@ dependencies = [
  "expect-test",
  "intern",
  "parser",
- "ra-ap-rustc_lexer 0.122.0",
+ "ra-ap-rustc_lexer 0.123.0",
  "rustc-hash 2.1.1",
  "smallvec",
  "span",
@@ -1495,7 +1495,7 @@ dependencies = [
  "drop_bomb",
  "edition",
  "expect-test",
- "ra-ap-rustc_lexer 0.122.0",
+ "ra-ap-rustc_lexer 0.123.0",
  "rustc-literal-escaper",
  "stdx",
  "tracing",
@@ -1605,7 +1605,7 @@ dependencies = [
  "object",
  "paths",
  "proc-macro-test",
- "ra-ap-rustc_lexer 0.122.0",
+ "ra-ap-rustc_lexer 0.123.0",
  "span",
  "syntax-bridge",
  "tt",
@@ -1748,9 +1748,9 @@ dependencies = [
 
 [[package]]
 name = "ra-ap-rustc_abi"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb01e1fec578003c85481c1cad4ff8cd8195b07c2dc85ae3f716108507ae15d5"
+checksum = "f18c877575c259d127072e9bfc41d985202262fb4d6bfdae3d1252147c2562c2"
 dependencies = [
  "bitflags 2.9.1",
  "ra-ap-rustc_hashes",
@@ -1760,18 +1760,18 @@ dependencies = [
 
 [[package]]
 name = "ra-ap-rustc_hashes"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e0ec056e72a472ffef8761ce96ece6c626eb07368c09d0105b6df30d27d07673"
+checksum = "2439ed1df3472443133b66949f81080dff88089b42f825761455463709ee1cad"
 dependencies = [
  "rustc-stable-hash",
 ]
 
 [[package]]
 name = "ra-ap-rustc_index"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0fcdd1001db0295e59052e9f53aeda588bbe81e362534f4687d41bd44777b5a7"
+checksum = "57a24fe0be21be1f8ebc21dcb40129214fb4cefb0f2753f3d46b6dbe656a1a45"
 dependencies = [
  "ra-ap-rustc_index_macros",
  "smallvec",
@@ -1779,9 +1779,9 @@ dependencies = [
 
 [[package]]
 name = "ra-ap-rustc_index_macros"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "728d64dd98e25530b32e3f7c7c1e844e52722b269360daa1cdeba9dff9727a26"
+checksum = "844a27ddcad0116facae2df8e741fd788662cf93dc13029cd864f2b8013b81f9"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1801,9 +1801,9 @@ dependencies = [
 
 [[package]]
 name = "ra-ap-rustc_lexer"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "415f0821f512608d825b3215489a6a6a2c18ed9f0045953d514e7ec23d4b90ab"
+checksum = "2b734cfcb577d09877799a22742f1bd398be6c00bc428d9de56d48d11ece5771"
 dependencies = [
  "memchr",
  "unicode-properties",
@@ -1822,9 +1822,9 @@ dependencies = [
 
 [[package]]
 name = "ra-ap-rustc_pattern_analysis"
-version = "0.122.0"
+version = "0.123.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4657fcfdfe06e2a02ec8180d4e7c95aecf4811ba50367e363d1a2300b7623284"
+checksum = "75b0ee1f059b9dea0818c6c7267478926eee95ba4c7dcf89c8db32fa165d3904"
 dependencies = [
  "ra-ap-rustc_index",
  "rustc-hash 2.1.1",
@@ -2590,7 +2590,7 @@ version = "0.0.0"
 dependencies = [
  "arrayvec",
  "intern",
- "ra-ap-rustc_lexer 0.122.0",
+ "ra-ap-rustc_lexer 0.123.0",
  "stdx",
  "text-size",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 87202e86d3..e7cf0212bf 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -89,11 +89,11 @@ vfs-notify = { path = "./crates/vfs-notify", version = "0.0.0" }
 vfs = { path = "./crates/vfs", version = "0.0.0" }
 edition = { path = "./crates/edition", version = "0.0.0" }
 
-ra-ap-rustc_lexer = { version = "0.122", default-features = false }
+ra-ap-rustc_lexer = { version = "0.123", default-features = false }
 ra-ap-rustc_parse_format = { version = "0.121", default-features = false }
-ra-ap-rustc_index = { version = "0.122", default-features = false }
-ra-ap-rustc_abi = { version = "0.122", default-features = false }
-ra-ap-rustc_pattern_analysis = { version = "0.122", default-features = false }
+ra-ap-rustc_index = { version = "0.123", default-features = false }
+ra-ap-rustc_abi = { version = "0.123", default-features = false }
+ra-ap-rustc_pattern_analysis = { version = "0.123", default-features = false }
 
 # local crates that aren't published to crates.io. These should not have versions.
 
diff --git a/crates/hir-ty/src/layout/adt.rs b/crates/hir-ty/src/layout/adt.rs
index 236f316366..3f310c26ec 100644
--- a/crates/hir-ty/src/layout/adt.rs
+++ b/crates/hir-ty/src/layout/adt.rs
@@ -85,16 +85,6 @@ pub fn layout_of_adt_query(
                 let d = db.const_eval_discriminant(e.enum_variants(db).variants[id.0].0).ok()?;
                 Some((id, d))
             }),
-            // FIXME: The current code for niche-filling relies on variant indices
-            // instead of actual discriminants, so enums with
-            // explicit discriminants (RFC #2363) would misbehave and we should disable
-            // niche optimization for them.
-            // The code that do it in rustc:
-            // repr.inhibit_enum_layout_opt() || def
-            //     .variants()
-            //     .iter_enumerated()
-            //     .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32()))
-            repr.inhibit_enum_layout_opt(),
             !matches!(def, AdtId::EnumId(..))
                 && variants
                     .iter()
diff --git a/rust-version b/rust-version
index c2b1c151b8..2178caf639 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-e05ab47e6c418fb2b9faa2eae9a7e70c65c98eaa
+733dab558992d902d6d17576de1da768094e2cf3