Remove is_proc_macro_dep.

rust/private/BUILD.bazel

@@ -1,6 +1,5 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("//rust/private:rust_analyzer.bzl", "rust_analyzer_detect_sysroot")
-load("//rust/private:rustc.bzl", "is_proc_macro_dep", "is_proc_macro_dep_enabled")
 
 # Exported for docs
 exports_files(["providers.bzl"])
@@ -32,24 +31,6 @@ bzl_library(
     ],
 )
 
-# This setting may be used to identify dependencies of proc-macro-s.
-# This feature is only enabled if `is_proc_macro_dep_enabled` is true.
-# Its value controls the BAZEL_RULES_RUST_IS_PROC_MACRO_DEP environment variable
-# made available to the rustc invocation.
-is_proc_macro_dep(
-    name = "is_proc_macro_dep",
-    build_setting_default = False,
-    visibility = ["//visibility:public"],
-)
-
-# This setting enables the feature to identify dependencies of proc-macro-s,
-# see `is_proc_macro_dep`.
-is_proc_macro_dep_enabled(
-    name = "is_proc_macro_dep_enabled",
-    build_setting_default = False,
-    visibility = ["//visibility:public"],
-)
-
 rust_analyzer_detect_sysroot(
     name = "rust_analyzer_detect_sysroot",
     visibility = ["//visibility:public"],

rust/private/rust.bzl

@@ -626,12 +626,6 @@ RUSTC_ATTRS = {
     "_extra_rustc_flags": attr.label(
         default = Label("//rust/settings:extra_rustc_flags"),
     ),
-    "_is_proc_macro_dep": attr.label(
-        default = Label("//rust/private:is_proc_macro_dep"),
-    ),
-    "_is_proc_macro_dep_enabled": attr.label(
-        default = Label("//rust/private:is_proc_macro_dep_enabled"),
-    ),
     "_per_crate_rustc_flag": attr.label(
         default = Label("//rust/settings:experimental_per_crate_rustc_flag"),
     ),
@@ -1108,40 +1102,10 @@ rust_shared_library = rule(
         """),
 )
 
-def _proc_macro_dep_transition_impl(settings, _attr):
-    if settings["//rust/private:is_proc_macro_dep_enabled"]:
-        return {"//rust/private:is_proc_macro_dep": True}
-    else:
-        return []
-
-_proc_macro_dep_transition = transition(
-    inputs = ["//rust/private:is_proc_macro_dep_enabled"],
-    outputs = ["//rust/private:is_proc_macro_dep"],
-    implementation = _proc_macro_dep_transition_impl,
-)
-
 rust_proc_macro = rule(
     implementation = _rust_proc_macro_impl,
     provides = COMMON_PROVIDERS,
-    # Start by copying the common attributes, then override the `deps` attribute
-    # to apply `_proc_macro_dep_transition`. To add this transition we additionally
-    # need to declare `_allowlist_function_transition`, see
-    # https://docs.bazel.build/versions/main/skylark/config.html#user-defined-transitions.
-    attrs = dict(
-        _COMMON_ATTRS.items(),
-        _allowlist_function_transition = attr.label(
-            default = Label("//tools/allowlists/function_transition_allowlist"),
-        ),
-        deps = attr.label_list(
-            doc = dedent("""\
-                List of other libraries to be linked to this library target.
-
-                These can be either other `rust_library` targets or `cc_library` targets if
-                linking a native library.
-            """),
-            cfg = _proc_macro_dep_transition,
-        ),
-    ),
+    attrs = _COMMON_ATTRS,
     fragments = ["cpp"],
     toolchains = [
         str(Label("//rust:toolchain_type")),

rust/private/rustc.bzl

@@ -101,34 +101,6 @@ PerCrateRustcFlagsInfo = provider(
     fields = {"per_crate_rustc_flags": "List[string] Extra flags to pass to rustc in non-exec configuration"},
 )
 
-IsProcMacroDepInfo = provider(
-    doc = "Records if this is a transitive dependency of a proc-macro.",
-    fields = {"is_proc_macro_dep": "Boolean"},
-)
-
-def _is_proc_macro_dep_impl(ctx):
-    return IsProcMacroDepInfo(is_proc_macro_dep = ctx.build_setting_value)
-
-is_proc_macro_dep = rule(
-    doc = "Records if this is a transitive dependency of a proc-macro.",
-    implementation = _is_proc_macro_dep_impl,
-    build_setting = config.bool(flag = True),
-)
-
-IsProcMacroDepEnabledInfo = provider(
-    doc = "Enables the feature to record if a library is a transitive dependency of a proc-macro.",
-    fields = {"enabled": "Boolean"},
-)
-
-def _is_proc_macro_dep_enabled_impl(ctx):
-    return IsProcMacroDepEnabledInfo(enabled = ctx.build_setting_value)
-
-is_proc_macro_dep_enabled = rule(
-    doc = "Enables the feature to record if a library is a transitive dependency of a proc-macro.",
-    implementation = _is_proc_macro_dep_enabled_impl,
-    build_setting = config.bool(flag = True),
-)
-
 def _get_rustc_env(attr, toolchain, crate_name):
     """Gathers rustc environment variables
 
@@ -161,11 +133,6 @@ def _get_rustc_env(attr, toolchain, crate_name):
         "CARGO_PKG_VERSION_PATCH": patch,
         "CARGO_PKG_VERSION_PRE": pre,
     }
-    if hasattr(attr, "_is_proc_macro_dep_enabled") and attr._is_proc_macro_dep_enabled[IsProcMacroDepEnabledInfo].enabled:
-        is_proc_macro_dep = "0"
-        if hasattr(attr, "_is_proc_macro_dep") and attr._is_proc_macro_dep[IsProcMacroDepInfo].is_proc_macro_dep:
-            is_proc_macro_dep = "1"
-        result["BAZEL_RULES_RUST_IS_PROC_MACRO_DEP"] = is_proc_macro_dep
     return result
 
 def get_compilation_mode_opts(ctx, toolchain):