rust-analyzer: unresolved-proc-macro error on all proc macro usages

rust-analyzer version: 3d63abf1d 2022-01-01 nightly

rustc version: rustc 1.57.0 (f1edd0429 2021-11-29)

I’ve verified that proc macro support is enabled by looking at the client logs:

INFO [1/1/2022, 4:49:27 AM]: Extension version: 0.3.886
INFO [1/1/2022, 4:49:27 AM]: Using configuration {
  cargoRunner: null,
  runnableEnv: null,
  inlayHints: {
    enable: false,
    smallerHints: true,
    chainingHints: true,
    maxLength: 25,
    parameterHints: true,
    typeHints: true,
    hideNamedConstructorHints: false
  },
  server: { path: null, extraEnv: null },
  trace: { server: 'off', extension: false },
  debug: {
    engine: 'auto',
    sourceFileMap: {
      '/rustc/<id>': '${env:USERPROFILE}/.rustup/toolchains/<toolchain-id>/lib/rustlib/src/rust'
    },
    openDebugPane: false,
    engineSettings: {}
  },
  assist: {
    importGranularity: 'crate',
    importEnforceGranularity: false,
    importPrefix: 'crate',
    importGroup: true,
    allowMergingIntoGlobImports: true
  },
  cache: { warmup: true },
  callInfo: { full: true },
  cargo: {
    autoreload: true,
    allFeatures: false,
    unsetTest: [ 'core' ],
    features: [],
    runBuildScripts: true,
    useRustcWrapperForBuildScripts: true,
    noDefaultFeatures: false,
    target: null,
    noSysroot: false
  },
  checkOnSave: {
    enable: true,
    allFeatures: null,
    allTargets: true,
    command: 'clippy',
    noDefaultFeatures: null,
    target: null,
    extraArgs: [],
    features: null,
    overrideCommand: null
  },
  completion: {
    addCallArgumentSnippets: true,
    addCallParenthesis: true,
    snippets: {
      'Arc::new': {
        postfix: 'arc',
        body: 'Arc::new(${receiver})',
        requires: 'std::sync::Arc',
        description: 'Put the expression into an `Arc`',
        scope: 'expr'
      },
      'Rc::new': {
        postfix: 'rc',
        body: 'Rc::new(${receiver})',
        requires: 'std::rc::Rc',
        description: 'Put the expression into an `Rc`',
        scope: 'expr'
      },
      'Box::pin': {
        postfix: 'pinbox',
        body: 'Box::pin(${receiver})',
        requires: 'std::boxed::Box',
        description: 'Put the expression into a pinned `Box`',
        scope: 'expr'
      },
      Ok: {
        postfix: 'ok',
        body: 'Ok(${receiver})',
        description: 'Wrap the expression in a `Result::Ok`',
        scope: 'expr'
      },
      Err: {
        postfix: 'err',
        body: 'Err(${receiver})',
        description: 'Wrap the expression in a `Result::Err`',
        scope: 'expr'
      },
      Some: {
        postfix: 'some',
        body: 'Some(${receiver})',
        description: 'Wrap the expression in an `Option::Some`',
        scope: 'expr'
      }
    },
    postfix: { enable: true },
    autoimport: { enable: true },
    autoself: { enable: true }
  },
  diagnostics: {
    enable: true,
    enableExperimental: true,
    disabled: [],
    remapPrefix: {},
    warningsAsHint: [],
    warningsAsInfo: []
  },
  experimental: { procAttrMacros: true },
  files: { watcher: 'client', excludeDirs: [] },
  highlightRelated: {
    references: true,
    exitPoints: true,
    breakPoints: true,
    yieldPoints: true
  },
  highlighting: { strings: true },
  hover: { documentation: true, linksInHover: true },
  hoverActions: {
    debug: true,
    enable: true,
    gotoTypeDef: true,
    implementations: true,
    references: false,
    run: true
  },
  joinLines: {
    joinElseIf: true,
    removeTrailingComma: true,
    unwrapTrivialBlock: true,
    joinAssignments: true
  },
  lens: {
    debug: true,
    enable: false,
    implementations: true,
    run: true,
    methodReferences: false,
    references: false,
    enumVariantReferences: false,
    forceCustomCommands: true
  },
  linkedProjects: [],
  lruCapacity: null,
  notifications: { cargoTomlNotFound: true },
  procMacro: { enable: true, server: null },
  runnables: { overrideCargo: null, cargoExtraArgs: [] },
  rustcSource: null,
  rustfmt: {
    extraArgs: [],
    overrideCommand: [ 'rustfmt' ],
    enableRangeFormatting: false
  },
  workspace: { symbol: { search: { scope: 'workspace', kind: 'only_types' } } }
}
INFO [1/1/2022, 4:49:27 AM]: PersistentState: { serverVersion: '0.3.886' }

However, I’m still getting the unresolved-proc-macro error that macros are not being expanded. Is there something else that has to be enabled or installed to turn this on? The User Manual doesn’t mention anything else. It does say “can also indicate project setup problems” but doesn’t indicate what those might be.