Switch from exclamation point to declare syntax for type-only properties

Author: marijnh

src/change.ts

@@ -529,9 +529,9 @@ function composeSets(setA: ChangeDesc, setB: ChangeDesc, mkSet = false): ChangeD
 
 class SectionIter {
   i = 0
-  len!: number
-  off!: number
-  ins!: number
+  declare len: number
+  declare off: number
+  declare ins: number
 
   constructor(readonly set: ChangeDesc) {
     this.next()

src/facet.ts

@@ -110,7 +110,7 @@ export class Facet<Input, Output = readonly Input[]> implements FacetReader<Outp
     return this.compute([field], state => get!(state.field(field)))
   }
 
-  tag!: Output
+  declare tag: Output
 }
 
 /// A facet reader can be used to fetch the value of a facet, through
@@ -138,7 +138,7 @@ const enum Provider { Static, Single, Multi }
 
 class FacetProvider<Input> {
   readonly id = nextID++
-  extension!: Extension // Kludge to convince the type system these count as extensions
+  declare extension: Extension // Kludge to convince the type system these count as extensions
 
   constructor(readonly dependencies: readonly Slot<any>[],
               readonly facet: Facet<Input, any>,
@@ -405,7 +405,7 @@ export const Prec = {
 
 class PrecExtension {
   constructor(readonly inner: Extension, readonly prec: number) {}
-  extension!: Extension
+  declare extension: Extension
 }
 
 
@@ -438,7 +438,7 @@ export class Compartment {
 
 export class CompartmentInstance {
   constructor(readonly compartment: Compartment, readonly inner: Extension) {}
-  extension!: Extension
+  declare extension: Extension
 }
 
 export interface DynamicSlot {

src/rangeset.ts

@@ -12,20 +12,20 @@ export abstract class RangeValue {
   /// The bias value at the start of the range. Determines how the
   /// range is positioned relative to other ranges starting at this
   /// position. Defaults to 0.
-  startSide!: number
+  declare startSide: number
   /// The bias value at the end of the range. Defaults to 0.
-  endSide!: number
+  declare endSide: number
 
   /// The mode with which the location of the range should be mapped
   /// when its `from` and `to` are the same, to decide whether a
   /// change deletes the range. Defaults to `MapMode.TrackDel`.
-  mapMode!: MapMode
+  declare mapMode: MapMode
   /// Determines whether this value marks a point range. Regular
   /// ranges affect the part of the document they cover, and are
   /// meaningless when empty. Point ranges have a meaning on their
   /// own. When non-empty, a point range is treated as atomic and
   /// shadows any ranges contained in it.
-  point!: boolean
+  declare point: boolean
 
   /// Create a [range](#state.Range) with this value.
   range(from: number, to = from) { return Range.create(from, to, this) }
@@ -540,12 +540,12 @@ function findSharedChunks(a: readonly RangeSet<any>[], b: readonly RangeSet<any>
 }
 
 class LayerCursor<T extends RangeValue> {
-  from!: number
-  to!: number
-  value!: T | null
+  declare from: number
+  declare to: number
+  declare value: T | null
 
-  chunkIndex!: number
-  rangeIndex!: number
+  declare chunkIndex: number
+  declare rangeIndex: number
 
   constructor(readonly layer: RangeSet<T>,
               readonly skip: Set<Chunk<T>> | null,
@@ -626,10 +626,10 @@ class LayerCursor<T extends RangeValue> {
 }
 
 class HeapCursor<T extends RangeValue> {
-  from!: number
-  to!: number
-  value!: T | null
-  rank!: number
+  declare from: number
+  declare to: number
+  declare value: T | null
+  declare rank: number
 
   constructor(readonly heap: LayerCursor<T>[]) {}
 

src/text.ts

@@ -147,7 +147,7 @@ export abstract class Text implements Iterable<string> {
   abstract readonly children: readonly Text[] | null
 
   /// @hide
-  [Symbol.iterator]!: () => Iterator<string>
+  declare [Symbol.iterator]: () => Iterator<string>
 
   /// Create a `Text` instance for the given array of lines.
   static of(text: readonly string[]): Text {
@@ -469,7 +469,7 @@ class RawTextCursor implements TextIterator {
   }
 
   /// @internal
-  [Symbol.iterator]!: () => Iterator<string>
+  declare [Symbol.iterator]: () => Iterator<string>
 }
 
 class PartialTextCursor implements TextIterator {
@@ -513,7 +513,7 @@ class PartialTextCursor implements TextIterator {
   get lineBreak() { return this.cursor.lineBreak && this.value != "" }
 
   /// @internal
-  [Symbol.iterator]!: () => Iterator<string>
+  declare [Symbol.iterator]: () => Iterator<string>
 }
 
 class LineCursor implements TextIterator {
@@ -548,7 +548,7 @@ class LineCursor implements TextIterator {
   get lineBreak() { return false }
 
   /// @internal
-  [Symbol.iterator]!: () => Iterator<string>
+  declare [Symbol.iterator]: () => Iterator<string>
 }
 
 if (typeof Symbol != "undefined") {

src/transaction.ts

@@ -26,7 +26,7 @@ export class Annotation<T> {
 
   // This is just to get less sloppy typing (where StateEffect is a subtype of Annotation)
   // @ts-ignore
-  private _isAnnotation!: true
+  declare private _isAnnotation: true
 }
 
 /// Marker that identifies a type of [annotation](#state.Annotation).