Update LLVM (#4807)

MODULE.bazel

@@ -116,8 +116,8 @@ bazel_dep(name = "zstd", version = "1.5.6", repo_name = "llvm_zstd")
 
 # We pin to specific upstream commits and try to track top-of-tree reasonably
 # closely rather than pinning to a specific release.
-# HEAD as of 2024-11-13.
-llvm_project_version = "97298853b4de70dbce9c0a140ac38e3ac179e02e"
+# HEAD as of 2025-01-15.
+llvm_project_version = "6ca560a9092e29c9f9817db6d6da09edd5f0ded7"
 
 # Load a repository for the raw llvm-project, pre-overlay.
 http_archive(
@@ -128,7 +128,7 @@ http_archive(
         "@carbon//bazel/llvm_project:0001_Patch_for_mallinfo2_when_using_Bazel_build_system.patch",
         "@carbon//bazel/llvm_project:0002_Added_Bazel_build_for_compiler_rt_fuzzer.patch",
     ],
-    sha256 = "ac811cb61d281043c865c39260a5114a0e96d16ec0e4eb74a2516a24981b9064",
+    sha256 = "1ee1e9baa236ac35c43b1a0878629f82b8ca0b85effe83aa697736a0b515923d",
     strip_prefix = "llvm-project-{0}".format(llvm_project_version),
     urls = ["https://github.com/llvm/llvm-project/archive/{0}.tar.gz".format(llvm_project_version)],
 )

explorer/ast/element.cpp

@@ -22,7 +22,7 @@ auto NamedElement::name() const -> std::string_view {
   if (const auto* decl = element_.dyn_cast<const Declaration*>()) {
     return GetName(*decl).value();
   } else {
-    const auto* named_value = element_.get<const NamedValue*>();
+    const auto* named_value = cast<const NamedValue*>(element_);
     return named_value->name;
   }
 }
@@ -31,7 +31,7 @@ auto NamedElement::type() const -> const Value& {
   if (const auto* decl = element_.dyn_cast<const Declaration*>()) {
     return decl->static_type();
   } else {
-    const auto* named_value = element_.get<const NamedValue*>();
+    const auto* named_value = cast<const NamedValue*>(element_);
     return *named_value->value;
   }
 }

explorer/interpreter/pattern_analysis.cpp

@@ -13,7 +13,7 @@ using llvm::isa;
 namespace Carbon {
 
 auto AbstractPattern::kind() const -> Kind {
-  if (value_.is<const Pattern*>()) {
+  if (isa<const Pattern*>(value_)) {
     return Compound;
   }
   if (const auto* value = value_.dyn_cast<const Value*>()) {
@@ -22,7 +22,7 @@ auto AbstractPattern::kind() const -> Kind {
     }
     return Primitive;
   }
-  CARBON_CHECK(value_.is<const WildcardTag*>());
+  CARBON_CHECK(isa<const WildcardTag*>(value_));
   return Wildcard;
 }
 
@@ -92,7 +92,7 @@ void AbstractPattern::AppendElementsTo(
 
 auto AbstractPattern::value() const -> const Value& {
   CARBON_CHECK(kind() == Primitive);
-  return *value_.get<const Value*>();
+  return *cast<const Value*>(value_);
 }
 
 auto AbstractPattern::type() const -> const Value& {