lean4-htt/src/Lean/Message.lean

/-
Copyright (c) 2018 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Sebastian Ullrich, Leonardo de Moura

Message type used by the Lean frontend
-/
prelude
import Lean.Data.Position
import Lean.Data.OpenDecl
import Lean.MetavarContext
import Lean.Environment
import Lean.Util.PPExt
import Lean.Util.Sorry

namespace Lean

def mkErrorStringWithPos (fileName : String) (pos : Position) (msg : String) (endPos : Option Position := none) : String :=
  let endPos := match endPos with
    | some endPos => s!"-{endPos.line}:{endPos.column}"
    | none        => ""
  s!"{fileName}:{pos.line}:{pos.column}{endPos}: {msg}"

inductive MessageSeverity where
  | information | warning | error
  deriving Inhabited, BEq, ToJson, FromJson

structure MessageDataContext where
  env  : Environment
  mctx : MetavarContext
  lctx : LocalContext
  opts : Options

/-- A naming context is the information needed to shorten names in pretty printing.

It gives the current namespace and the list of open declarations.
-/
structure NamingContext where
  currNamespace : Name
  openDecls : List OpenDecl

structure TraceData where
  /-- Trace class, e.g. `Elab.step`. -/
  cls       : Name
  /-- Start time in seconds; 0 if unknown to avoid `Option` allocation. -/
  startTime : Float := 0
  /-- Stop time in seconds; 0 if unknown to avoid `Option` allocation. -/
  stopTime  : Float := startTime
  /-- Whether trace node defaults to collapsed in the infoview. -/
  collapsed : Bool := true
  /-- Optional tag shown in `trace.profiler.output` output after the trace class name. -/
  tag       : String := ""

/-- Structured message data. We use it for reporting errors, trace messages, etc. -/
inductive MessageData where
  /-- Eagerly formatted text with info annotations.
  This constructor is inspected in various hacks. -/
  | ofFormatWithInfos : FormatWithInfos → MessageData
  | ofGoal            : MVarId → MessageData
  /-- A widget instance.

  In `ofWidget wi alt`,
  the nested message `alt` should approximate the contents of the widget
  without itself using `ofWidget wi _`.
  This is used as fallback in environments that cannot display user widgets.
  `alt` may nest any structured message,
  for example `ofGoal` to approximate a tactic state widget,
  and, if necessary, even other widget instances
  (for which approximations are computed recursively).

  Note that unlike with `Widget.savePanelWidgetInfo`,
  the infoview will not pass any additional props to the widget instance. -/
  | ofWidget          : Widget.WidgetInstance → MessageData → MessageData
  /-- `withContext ctx d` specifies the pretty printing context `(env, mctx, lctx, opts)` for the nested expressions in `d`. -/
  | withContext       : MessageDataContext → MessageData → MessageData
  | withNamingContext : NamingContext → MessageData → MessageData
  /-- Lifted `Format.nest` -/
  | nest              : Nat → MessageData → MessageData
  /-- Lifted `Format.group` -/
  | group             : MessageData → MessageData
  /-- Lifted `Format.compose` -/
  | compose           : MessageData → MessageData → MessageData
  /-- Tagged sections. `Name` should be viewed as a "kind", and is used by `MessageData` inspector functions.
    Example: an inspector that tries to find "definitional equality failures" may look for the tag "DefEqFailure". -/
  | tagged            : Name → MessageData → MessageData
  | trace (data : TraceData) (msg : MessageData) (children : Array MessageData)
  /-- A lazy message.
  The provided thunk will not be run until it is about to be displayed.
  This can save computation in cases where the message may never be seen.

  The `Dynamic` value is expected to be a `MessageData`,
  which is a workaround for the positivity restriction.

  If the thunked message is produced for a term that contains a synthetic sorry,
  `hasSyntheticSorry` should return `true`.
  This is used to filter out certain messages. -/
  | ofLazy (f : Option PPContext → BaseIO Dynamic) (hasSyntheticSorry : MetavarContext → Bool)
  deriving Inhabited, TypeName

namespace MessageData

/-- Eagerly formatted text. -/
def ofFormat (fmt : Format) : MessageData := .ofFormatWithInfos ⟨fmt, .empty⟩

/--
Lazy message data production, with access to the context as given by
a surrounding `MessageData.withContext` (which is expected to exist).
-/
def lazy (f : PPContext → BaseIO MessageData)
    (hasSyntheticSorry : MetavarContext → Bool := fun _ => false)
    (onMissingContext : Unit → BaseIO MessageData :=
      fun _ => pure (.ofFormat "(invalid MessageData.lazy, missing context)")) : MessageData :=
  .ofLazy (hasSyntheticSorry := hasSyntheticSorry) fun ctx? => do
    let msg ← match ctx? with
      | .none => onMissingContext ()
      | .some ctx => f ctx
    return Dynamic.mk msg

variable (p : Name → Bool) in
/-- Returns true when the message contains a `MessageData.tagged tag ..` constructor where `p tag`
is true.

This does not descend into lazily generated subtrees (`.ofLazy`); message tags
of interest (like those added by `logLinter`) are expected to be near the root
of the `MessageData`, and not hidden inside `.ofLazy`.
-/
partial def hasTag : MessageData → Bool
  | withContext _ msg       => hasTag msg
  | withNamingContext _ msg => hasTag msg
  | nest _ msg              => hasTag msg
  | group msg               => hasTag msg
  | compose msg₁ msg₂       => hasTag msg₁ || hasTag msg₂
  | tagged n msg            => p n || hasTag msg
  | trace data msg msgs     => p data.cls || hasTag msg || msgs.any hasTag
  | _                       => false

/--
Returns the top-level tag of the message.
If none, returns `Name.anonymous`.

This does not descend into message subtrees (e.g., `.compose`, `.ofLazy`).
The message kind is expected to describe the whole message.
-/
def kind : MessageData → Name
  | withContext _ msg       => kind msg
  | withNamingContext _ msg => kind msg
  | tagged n _              => n
  | _                       => .anonymous

def isTrace : MessageData → Bool
  | withContext _ msg       => msg.isTrace
  | withNamingContext _ msg => msg.isTrace
  | tagged _ msg            => msg.isTrace
  | .trace _ _ _            => true
  | _                       => false

/-- An empty message. -/
def nil : MessageData :=
  ofFormat Format.nil

def mkPPContext (nCtx : NamingContext) (ctx : MessageDataContext) : PPContext := {
  env := ctx.env, mctx := ctx.mctx, lctx := ctx.lctx, opts := ctx.opts,
  currNamespace := nCtx.currNamespace, openDecls := nCtx.openDecls
}

def ofSyntax (stx : Syntax) : MessageData :=
  -- discard leading/trailing whitespace
  let stx := stx.copyHeadTailInfoFrom .missing
  .ofLazy
    (fun ctx? => do
      let msg ← ofFormat <$> match ctx? with
        | .none => pure stx.formatStx
        | .some ctx => ppTerm ctx ⟨stx⟩ -- HACK: might not be a term
      return Dynamic.mk msg)
    (fun _ => false)

def ofExpr (e : Expr) : MessageData :=
  .ofLazy
    (fun ctx? => do
      let msg ← ofFormatWithInfos <$> match ctx? with
        | .none => pure (format (toString e))
        | .some ctx => ppExprWithInfos ctx e
      return Dynamic.mk msg)
    (fun mctx => instantiateMVarsCore mctx e |>.1.hasSyntheticSorry)

def ofLevel (l : Level) : MessageData :=
  .ofLazy
    (fun ctx? => do
      let msg ← ofFormat <$> match ctx? with
        | .none => pure (format l)
        | .some ctx => ppLevel ctx l
      return Dynamic.mk msg)
    (fun _ => false)

/--
Simply formats the name.
See `MessageData.ofConstName` for richer messages.
-/
def ofName (n : Name) : MessageData := ofFormat (format n)

/--
Represents a constant name such that hovering and "go to definition" works.
If there is no such constant in the environment, the name is simply formatted, but sanitized if it is a hygienic name.
Use `MessageData.ofName` if hovers are undesired.

If `fullNames` is true, then pretty prints as if `pp.fullNames` is true.
Otherwise, pretty prints using the current user setting for `pp.fullNames`.
-/
def ofConstName (constName : Name) (fullNames : Bool := false) : MessageData :=
  .ofLazy
    (fun ctx? => do
      let msg ← ofFormatWithInfos <$> match ctx? with
        | .none => pure (format constName)
        | .some ctx =>
          let ctx := if fullNames then { ctx with opts := ctx.opts.insert `pp.fullNames fullNames } else ctx
          ppConstNameWithInfos ctx constName
      return Dynamic.mk msg)
    (fun _ => false)

partial def hasSyntheticSorry (msg : MessageData) : Bool :=
  visit none msg
where
  visit (mctx? : Option MetavarContext) : MessageData → Bool
  | ofLazy _ f              => f (mctx?.getD {})
  | withContext ctx msg     => visit ctx.mctx msg
  | withNamingContext _ msg => visit mctx? msg
  | nest _ msg              => visit mctx? msg
  | group msg               => visit mctx? msg
  | compose msg₁ msg₂       => visit mctx? msg₁ || visit mctx? msg₂
  | tagged _ msg            => visit mctx? msg
  | trace _ msg msgs        => visit mctx? msg || msgs.any (visit mctx?)
  | _                       => false

/--
Maximum number of trace node children to display by default to prevent slowdowns from rendering. In
the info view, more children can be expanded interactively.
-/
register_option maxTraceChildren : Nat := {
  defValue := 50
  descr := "Maximum number of trace node children to display"
}

partial def formatAux : NamingContext → Option MessageDataContext → MessageData → BaseIO Format
  | _,    _,         ofFormatWithInfos fmt    => return fmt.1
  | _,    none,      ofGoal mvarId            => return formatRawGoal mvarId
  | nCtx, some ctx,  ofGoal mvarId            => ppGoal (mkPPContext nCtx ctx) mvarId
  | nCtx, ctx,       ofWidget _ d             => formatAux nCtx ctx d
  | nCtx, _,         withContext ctx d        => formatAux nCtx ctx d
  | _,    ctx,       withNamingContext nCtx d => formatAux nCtx ctx d
  | nCtx, ctx,       tagged _ d               => formatAux nCtx ctx d
  | nCtx, ctx,       nest n d                 => Format.nest n <$> formatAux nCtx ctx d
  | nCtx, ctx,       compose d₁ d₂            => return (← formatAux nCtx ctx d₁) ++ (← formatAux nCtx ctx d₂)
  | nCtx, ctx,       group d                  => Format.group <$> formatAux nCtx ctx d
  | nCtx, ctx,       trace data header children => do
    let childFmts ← children.mapM (formatAux nCtx ctx)
    if data.cls.isAnonymous then
      -- Sequence of top-level traces collected by `addTraceAsMessages`, do not indent.
      return .joinSep childFmts.toList "\n"

    let mut msg := f!"[{data.cls}]"
    if data.startTime != 0 then
      msg := f!"{msg} [{data.stopTime - data.startTime}]"
    msg := f!"{msg} {(← formatAux nCtx ctx header).nest 2}"
    let mut children := children
    if let some maxNum := ctx.map (maxTraceChildren.get ·.opts) then
      if maxNum > 0 && children.size > maxNum then
        children := children.take maxNum |>.push <|
          ofFormat f!"{children.size - maxNum} more entries... (increase `maxTraceChildren` to see more)"
    return .nest 2 (.joinSep (msg::childFmts.toList) "\n")
  | nCtx, ctx?,      ofLazy pp _             => do
    let dyn ← pp (ctx?.map (mkPPContext nCtx))
    let some msg := dyn.get? MessageData
      | panic! s!"MessageData.ofLazy: expected MessageData in Dynamic, got {dyn.typeName}"
    formatAux nCtx ctx? msg

protected def format (msgData : MessageData) (ctx? : Option MessageDataContext := none) : BaseIO Format :=
  formatAux { currNamespace := Name.anonymous, openDecls := [] } ctx? msgData

protected def toString (msgData : MessageData) : BaseIO String := do
  return toString (← msgData.format)

instance : Append MessageData := ⟨compose⟩

instance : Coe String MessageData := ⟨ofFormat ∘ format⟩
instance : Coe Format MessageData := ⟨ofFormat⟩
instance : Coe Level MessageData  := ⟨ofLevel⟩
instance : Coe Expr MessageData   := ⟨ofExpr⟩
instance : Coe Name MessageData   := ⟨ofName⟩
instance : Coe Syntax MessageData := ⟨ofSyntax⟩
instance : Coe MVarId MessageData := ⟨ofGoal⟩
instance : Coe (Option Expr) MessageData := ⟨fun o => match o with | none => "none" | some e => ofExpr e⟩

partial def arrayExpr.toMessageData (es : Array Expr) (i : Nat) (acc : MessageData) : MessageData :=
  if h : i < es.size then
    let e   := es[i];
    let acc := if i == 0 then acc ++ ofExpr e else acc ++ ", " ++ ofExpr e;
    toMessageData es (i+1) acc
  else
    acc ++ "]"

instance : Coe (Array Expr) MessageData := ⟨fun es => arrayExpr.toMessageData es 0 "#["⟩

/-- Wrap the given message in `l` and `r`. See also `Format.bracket`.  -/
def bracket (l : String) (f : MessageData) (r : String) : MessageData := group (nest l.length <| l ++ f ++ r)
/-- Wrap the given message in parentheses `()`. -/
def paren (f : MessageData) : MessageData := bracket "(" f ")"
/-- Wrap the given message in square brackets `[]`. -/
def sbracket (f : MessageData) : MessageData := bracket "[" f "]"
/-- Append the given list of messages with the given separator. -/
def joinSep : List MessageData → MessageData → MessageData
  | [],    _   => Format.nil
  | [a],   _   => a
  | a::as, sep => a ++ sep ++ joinSep as sep

/-- Write the given list of messages as a list, separating each item with `,\n` and surrounding with square brackets. -/
def ofList : List MessageData → MessageData
  | [] => "[]"
  | xs => sbracket <| joinSep xs (ofFormat "," ++ Format.line)

/-- See `MessageData.ofList`. -/
def ofArray (msgs : Array MessageData) : MessageData :=
  ofList msgs.toList

/--
Puts `MessageData` into a comma-separated list with `"or"` at the back (with the serial comma).

Best used on non-empty lists; returns `"– none –"` for an empty list.
-/
def orList (xs : List MessageData) : MessageData :=
  match xs with
  | [] => "– none –"
  | [x] => x
  | [x₀, x₁] => x₀ ++ " or " ++ x₁
  | _ => joinSep xs.dropLast ", " ++ ", or " ++ xs.getLast!

/--
Puts `MessageData` into a comma-separated list with `"and"` at the back (with the serial comma).

Best used on non-empty lists; returns `"– none –"` for an empty list.
-/
def andList (xs : List MessageData) : MessageData :=
  match xs with
  | [] => "– none –"
  | [x] => x
  | [x₀, x₁] => x₀ ++ " and " ++ x₁
  | _ => joinSep xs.dropLast ", " ++ ", and " ++ xs.getLast!

/--
Produces a labeled note that can be appended to an error message.
-/
def note (note : MessageData) : MessageData :=
  -- Note: we do not use the built-in string coercion because it can prevent proper line breaks
  .tagged `note <| .compose (.ofFormat .line) <| .compose (.ofFormat .line) <|
    .compose "Note: " note

/--
Produces a labeled hint without an associated code action (non-monadic variant of
`MessageData.hint`).
-/
def hint' (hint : MessageData) : MessageData :=
  .tagged `hint <| .compose (.ofFormat .line) <| .compose (.ofFormat .line) <|
    .compose "Hint: " hint

instance : Coe (List MessageData) MessageData := ⟨ofList⟩
instance : Coe (List Expr) MessageData := ⟨fun es => ofList <| es.map ofExpr⟩

end MessageData

/--
A `BaseMessage` is a richly formatted piece of information emitted by Lean.
They are rendered by client editors in the infoview and in diagnostic windows.
There are two varieties in the Lean core:
* `Message`: Uses structured, effectful `MessageData` for formatting content.
* `SerialMessage`: Stores pure `String` data. Obtained by running the effectful
`Message.serialize`.
-/
structure BaseMessage (α : Type u) where
  fileName      : String
  pos           : Position
  endPos        : Option Position := none
  /-- If `true`, report range as given; see `msgToInteractiveDiagnostic`. -/
  keepFullRange : Bool := false
  severity      : MessageSeverity := .error
  /--
  If `true`, filter this message from non-language server output.
  In the language server, silent messages are served as silent diagnostics.
  See also `DiagnosticWith.isSilent?`.
  -/
  isSilent      : Bool := false
  caption       : String          := ""
  /-- The content of the message. -/
  data          : α
  deriving Inhabited, ToJson, FromJson

/-- A `Message` is a richly formatted piece of information emitted by Lean.
They are rendered by client editors in the infoview and in diagnostic windows. -/
abbrev Message := BaseMessage MessageData

/-- A `SerialMessage` is a `Message` whose `MessageData` has been eagerly
serialized and is thus appropriate for use in pure contexts where the effectful
`MessageData.toString` cannot be used. -/
structure SerialMessage extends BaseMessage String where
  /-- The message kind (i.e., the top-level tag). -/
  kind          : Name
  deriving ToJson, FromJson

namespace SerialMessage

@[inline] def toMessage (msg : SerialMessage) : Message :=
  {msg with data := msg.data}

protected def toString (msg : SerialMessage) (includeEndPos := false) : String := Id.run do
  let mut str := msg.data
  let endPos := if includeEndPos then msg.endPos else none
  unless msg.caption == "" do
    str := msg.caption ++ ":\n" ++ str
  match msg.severity with
  | .information => pure ()
  | .warning     => str := mkErrorStringWithPos msg.fileName msg.pos (endPos := endPos) "warning: " ++ str
  | .error       => str := mkErrorStringWithPos msg.fileName msg.pos (endPos := endPos) "error: " ++ str
  if str.isEmpty || str.back != '\n' then
    str := str ++ "\n"
  return str

instance : ToString SerialMessage := ⟨SerialMessage.toString⟩

end SerialMessage

namespace Message

@[inherit_doc MessageData.kind] abbrev kind (msg : Message) :=
  msg.data.kind

def isTrace (msg : Message) : Bool :=
  msg.data.isTrace

/-- Serializes the message, converting its data into a string and saving its kind. -/
@[inline] def serialize (msg : Message) : BaseIO SerialMessage := do
  return {msg with kind := msg.kind, data := ← msg.data.toString}

protected def toString (msg : Message) (includeEndPos := false) : BaseIO String := do
  -- Remark: The inline here avoids a new message allocation when `msg` is shared
  return inline <| (← msg.serialize).toString includeEndPos

protected def toJson (msg : Message) : BaseIO Json := do
  -- Remark: The inline here avoids a new message allocation when `msg` is shared
  return inline <| toJson (← msg.serialize)

end Message

/--
A persistent array of messages.

In the Lean elaborator, we use a fresh message log per command but may also report diagnostics at
various points inside a command, which will empty `unreported` and move its messages to `reported`.
Reported messages are preserved for some specific "lookback" operations such as `hasError` that
should consider the entire message history of the current command; most other functions such as
`add` and `toList` will only operate on unreported messages.
-/
structure MessageLog where
  /-- The list of messages already reported (i.e. saved in a `Snapshot`), in insertion order. -/
  reported : PersistentArray Message := {}
  /-- The list of messages not already reported, in insertion order. -/
  unreported : PersistentArray Message := {}
  /--
  Set of message kinds that have been added to the log.
  For example, we have the kind `unsafe.exponentiation.warning` for warning messages associated with
  the configuration option `exponentiation.threshold`.
  We don't produce a warning if the kind is already in the following set.
  -/
  loggedKinds : NameSet := {}
  deriving Inhabited

namespace MessageLog
def empty : MessageLog := {}

-- Despite having been deprecated, the archived `LeanInk` project (which CI still uses)
-- relies on this name.
@[deprecated "renamed to `unreported`; direct access should in general be avoided in favor of \
using `MessageLog.toList/toArray`" (since := "2024-05-22")]
def msgs : MessageLog → PersistentArray Message := unreported

def reportedPlusUnreported : MessageLog → PersistentArray Message
  | { reported := r, unreported := u, .. } => r ++ u

def hasUnreported (log : MessageLog) : Bool :=
  !log.unreported.isEmpty

def add (msg : Message) (log : MessageLog) : MessageLog :=
  { log with unreported := log.unreported.push msg }

protected def append (l₁ l₂ : MessageLog) : MessageLog where
  reported := l₁.reported ++ l₂.reported
  unreported := l₁.unreported ++ l₂.unreported
  loggedKinds := l₁.loggedKinds.union l₂.loggedKinds

instance : Append MessageLog :=
  ⟨MessageLog.append⟩

/--
Checks if either of `reported` or `unreported` contains an error, i.e. whether the current command
has errored yet.
-/
def hasErrors (log : MessageLog) : Bool :=
  log.reported.any (·.severity matches .error) || log.unreported.any (·.severity matches .error)

/-- Moves `unreported` messages to `reported`. -/
def markAllReported (log : MessageLog) : MessageLog :=
  { log with unreported := {}, reported := log.reported ++ log.unreported }

def errorsToWarnings (log : MessageLog) : MessageLog :=
  { unreported := log.unreported.map (fun m => match m.severity with | MessageSeverity.error => { m with severity := MessageSeverity.warning } | _ => m) }

def errorsToInfos (log : MessageLog) : MessageLog :=
  { unreported := log.unreported.map (fun m => match m.severity with | MessageSeverity.error => { m with severity := MessageSeverity.information } | _ => m) }

def getInfoMessages (log : MessageLog) : MessageLog :=
  { unreported := log.unreported.filter fun m => match m.severity with | MessageSeverity.information => true | _ => false }

def forM {m : Type → Type} [Monad m] (log : MessageLog) (f : Message → m Unit) : m Unit :=
  log.unreported.forM f

/-- Converts the unreported messages to a list, oldest message first. -/
def toList (log : MessageLog) : List Message :=
  log.unreported.toList

/-- Converts the unreported messages to an array, oldest message first. -/
def toArray (log : MessageLog) : Array Message :=
  log.unreported.toArray

end MessageLog

def MessageData.nestD (msg : MessageData) : MessageData :=
  MessageData.nest 2 msg

def indentD (msg : MessageData) : MessageData :=
  MessageData.nestD (Format.line ++ msg)

def indentExpr (e : Expr) : MessageData :=
  indentD e

/--
Returns the character length of the message when rendered.

Note: this is a potentially expensive operation that is only relevant to message data that are
actually rendered. Consider using this function in lazy message data to avoid unnecessary
computation for messages that are not displayed.
-/
private def MessageData.formatLength (ctx : PPContext) (msg : MessageData) : BaseIO Nat := do
  let { env, mctx, lctx, opts, ..} := ctx
  let fmt ← msg.format (some { env, mctx, lctx, opts })
  return fmt.pretty.length


/--
Renders an expression `e` inline in a message unless it will exceed `maxInlineLength` characters, in
which case the expression is indented on a new line.

Note that the output of this function is formatted with preceding and trailing space included. Thus,
in `m₁ ++ inlineExpr e ++ m₂`, `m₁` should not end with a space or new line, nor should `m₂` begin
with one.
-/
def inlineExpr (e : Expr) (maxInlineLength := 30) : MessageData :=
  .lazy
    (fun ctx => do
      let msg := MessageData.ofExpr e
      if (← msg.formatLength ctx) > maxInlineLength then
        return indentD msg ++ "\n"
      else
        return " " ++ msg ++ " ")
    (fun mctx => instantiateMVarsCore mctx e |>.1.hasSyntheticSorry)
    (fun () => return " " ++ MessageData.ofExpr e ++ " ")

/-- Atom quotes -/
def aquote (msg : MessageData) : MessageData :=
  "「" ++ msg ++ "」"

class AddMessageContext (m : Type → Type) where
  /--
  Without context, a `MessageData` object may be missing information
  (e.g. hover info) for pretty printing, or may print an error. Hence,
  `addMessageContext` should be called on all constructed `MessageData`
  (e.g. via `m!`) before taking it out of context (e.g. leaving `MetaM` or
  `CoreM`).
  -/
  addMessageContext : MessageData → m MessageData

export AddMessageContext (addMessageContext)

instance (m n) [MonadLift m n] [AddMessageContext m] : AddMessageContext n where
  addMessageContext := fun msg => liftM (addMessageContext msg : m _)

def addMessageContextPartial {m} [Monad m] [MonadEnv m] [MonadOptions m] (msgData : MessageData) : m MessageData := do
  let env ← getEnv
  let opts ← getOptions
  return MessageData.withContext { env := env, mctx := {}, lctx := {}, opts := opts } msgData

def addMessageContextFull {m} [Monad m] [MonadEnv m] [MonadMCtx m] [MonadLCtx m] [MonadOptions m] (msgData : MessageData) : m MessageData := do
  let env ← getEnv
  let mctx ← getMCtx
  let lctx ← getLCtx
  let opts ← getOptions
  return MessageData.withContext { env := env, mctx := mctx, lctx := lctx, opts := opts } msgData

class ToMessageData (α : Type) where
  toMessageData : α → MessageData

export ToMessageData (toMessageData)

def stringToMessageData (str : String) : MessageData :=
  let lines := str.split (· == '\n')
  let lines := lines.map (MessageData.ofFormat ∘ format)
  MessageData.joinSep lines (MessageData.ofFormat Format.line)

instance [ToFormat α] : ToMessageData α := ⟨MessageData.ofFormat ∘ format⟩
instance : ToMessageData Expr          := ⟨MessageData.ofExpr⟩
instance : ToMessageData Level         := ⟨MessageData.ofLevel⟩
instance : ToMessageData Name          := ⟨MessageData.ofName⟩
instance : ToMessageData String        := ⟨stringToMessageData⟩
instance : ToMessageData Syntax        := ⟨MessageData.ofSyntax⟩
instance : ToMessageData (TSyntax k)   := ⟨(MessageData.ofSyntax ·)⟩
instance : ToMessageData Format        := ⟨MessageData.ofFormat⟩
instance : ToMessageData MVarId        := ⟨MessageData.ofGoal⟩
@[default_instance]
instance : ToMessageData MessageData   := ⟨id⟩
instance [ToMessageData α] : ToMessageData (List α)  := ⟨fun as => MessageData.ofList <| as.map toMessageData⟩
instance [ToMessageData α] : ToMessageData (Array α) := ⟨fun as => toMessageData as.toList⟩
instance [ToMessageData α] : ToMessageData (Subarray α) := ⟨fun as => toMessageData as.toArray.toList⟩
instance [ToMessageData α] : ToMessageData (Option α) := ⟨fun | none => "none" | some e => "some (" ++ toMessageData e ++ ")"⟩
instance [ToMessageData α] [ToMessageData β] : ToMessageData (α × β) :=
  ⟨fun (a, b) => .paren <| toMessageData a ++ "," ++ Format.line ++ toMessageData b⟩
instance : ToMessageData (Option Expr) := ⟨fun | none => "<not-available>" | some e => toMessageData e⟩

syntax:max "m!" interpolatedStr(term) : term

macro_rules
  | `(m! $interpStr) => do interpStr.expandInterpolatedStr (← `(MessageData)) (← `(toMessageData))

def toMessageList (msgs : Array MessageData) : MessageData :=
  indentD (MessageData.joinSep msgs.toList m!"\n\n")

namespace Kernel.Exception

private def mkCtx (env : Environment) (lctx : LocalContext) (opts : Options) (msg : MessageData) : MessageData :=
  MessageData.withContext { env := .ofKernelEnv env, mctx := {}, lctx := lctx, opts := opts } msg

def toMessageData (e : Kernel.Exception) (opts : Options) : MessageData :=
  match e with
  | unknownConstant env constName       => mkCtx env {} opts m!"(kernel) unknown constant '{constName}'"
  | alreadyDeclared env constName       => mkCtx env {} opts m!"(kernel) constant has already been declared '{.ofConstName constName true}'"
  | declTypeMismatch env decl givenType =>
    mkCtx env {} opts <|
    let process (n : Name) (expectedType : Expr) : MessageData :=
      m!"(kernel) declaration type mismatch, '{n}' has type{indentExpr givenType}\nbut it is expected to have type{indentExpr expectedType}";
    match decl with
    | Declaration.defnDecl { name := n, type := type, .. } => process n type
    | Declaration.thmDecl { name := n, type := type, .. }  => process n type
    | _ => "(kernel) declaration type mismatch" -- TODO fix type checker, type mismatch for mutual decls does not have enough information
  | declHasMVars env constName _        => mkCtx env {} opts m!"(kernel) declaration has metavariables '{.ofConstName constName true}'"
  | declHasFVars env constName _        => mkCtx env {} opts m!"(kernel) declaration has free variables '{.ofConstName constName true}'"
  | funExpected env lctx e              => mkCtx env lctx opts m!"(kernel) function expected{indentExpr e}"
  | typeExpected env lctx e             => mkCtx env lctx opts m!"(kernel) type expected{indentExpr e}"
  | letTypeMismatch  env lctx n _ _     => mkCtx env lctx opts m!"(kernel) let-declaration type mismatch '{n}'"
  | exprTypeMismatch env lctx e _       => mkCtx env lctx opts m!"(kernel) type mismatch at{indentExpr e}"
  | appTypeMismatch  env lctx e fnType argType =>
    mkCtx env lctx opts m!"(kernel) application type mismatch{indentExpr e}\nargument has type{indentExpr argType}\nbut function has type{indentExpr fnType}"
  | invalidProj env lctx e              => mkCtx env lctx opts m!"(kernel) invalid projection{indentExpr e}"
  | thmTypeIsNotProp env constName type => mkCtx env {} opts m!"(kernel) type of theorem '{.ofConstName constName true}' is not a proposition{indentExpr type}"
  | other msg                           => m!"(kernel) {msg}"
  | deterministicTimeout                => "(kernel) deterministic timeout"
  | excessiveMemory                     => "(kernel) excessive memory consumption detected"
  | deepRecursion                       => "(kernel) deep recursion detected"
  | interrupted                         => "(kernel) interrupted"

end Kernel.Exception

/-- Helper functions for creating a `MessageData` with the given header and elements. -/
def toTraceElem [ToMessageData α] (e : α) (cls : Name := Name.mkSimple "_") : MessageData :=
  .trace { cls } (toMessageData e) #[]

end Lean