Add support for SymbolInformation.signature

Companion PRs:

* sourcegraph/scip#231
* sourcegraph/cody#3142

Previously, scip-typescript didn't emit any structured information about
signatures. This PR solves that problem, which unblocks new exciting
use-cases for SCIP.

Keeping this PR open for a while since we are not planning to merge
signature support to SCIP just yet. For now, the Cody repo can use this
branch instead.

Author: olafurpg

.vscode/settings.json

@@ -1,3 +1,4 @@
 {
-  "editor.formatOnSave": true
+  "editor.formatOnSave": true,
+  "editor.defaultFormatter": "esbenp.prettier-vscode"
 }

snapshots/input/syntax/package.json

@@ -8,5 +8,8 @@
   },
   "author": "",
   "license": "ISC",
-  "private": true
+  "private": true,
+  "devDependencies": {
+    "@types/vscode": "1.86.0"
+  }
 }

snapshots/input/syntax/src/definition-file-signatures.d.ts

@@ -0,0 +1,14 @@
+// format-options: showSignatures
+export namespace minimized {
+  export enum NumericLiteralEnum {
+    One = 1,
+    TwoThousand = 2_000,
+  }
+
+  export const doubleConstant = 3.14
+
+  export enum StringLiteralEnum {
+    Saturday = 'saturday',
+    Sunday = 'sunday',
+  }
+}

snapshots/input/syntax/src/minimized-signatures.ts

@@ -0,0 +1,4 @@
+// format-options: showSignatures
+
+export type CompletionItemID = string & { _opaque: typeof CompletionItemID }
+declare const CompletionItemID: unique symbol

snapshots/input/syntax/src/signatures.ts

@@ -0,0 +1,99 @@
+// format-options: showSignatures
+
+export type Requests = {
+  'workspace/edit': [WorkspaceEditParams, boolean]
+  'chat/submitMessage': [WorkspaceEditParams, boolean]
+}
+
+export type Notifications = {
+  'workspace/edit': [WorkspaceEditParams]
+}
+
+export type Intersection = { uri: string } & { size: number }
+export type Union = { uri: string } | { size: number }
+export type Builtin = Pick<WorkspaceEditParams, 'changes'>
+export type Builtin2 = Partial<WorkspaceEditParams>
+export interface WorkspaceEditParams {
+  changes: { uri: string }[]
+}
+
+export interface ExampleSuperInterface<T> {
+  a: T
+  b: string
+}
+export interface ExampleInterface<T> extends ExampleSuperInterface<T> {
+  c: number
+}
+export class ExampleSuperClass<T> {
+  constructor(
+    public a: T,
+    public b: string
+  ) {}
+}
+
+export class ExampleClass<T>
+  extends ExampleSuperClass<T>
+  implements ExampleSuperInterface<T>, ExampleInterface<T>
+{
+  public d: Record<string, any>
+
+  #e = true
+
+  constructor(
+    public a: T,
+    public b: string,
+    public c: number,
+    d: Record<string, any>
+  ) {
+    super(a, b)
+    this.d = d
+  }
+  public getC(): number {
+    return this.c
+  }
+
+  get e(): boolean {
+    return this.#e
+  }
+
+  set setB(b: string) {
+    this.#e = true
+    this.b = b
+  }
+}
+
+export function basicFunction<T>(a: T, b: number): string {
+  return `${a}${b}`
+}
+export const constant = 42
+export const variable: <T>(a: T, b: number) => string = (a, b) => `${a}${b}`
+
+export interface User {
+  name: string
+  age: number
+  customHeaders: Record<string, string>
+}
+
+export interface ChatHistory {
+  chatID: User
+  [a: number]: User
+  [_: string]: User
+}
+
+export class ModelProvider {
+  default = true
+}
+
+export enum NumericLiteralEnum {
+  MinusOne = -1,
+  Expression = 1 + 23 - 2,
+  One = 1,
+  TwoThousand = 2_000,
+}
+
+export const doubleConstant = 3.14
+
+export enum StringLiteralEnum {
+  Saturday = 'saturday',
+  Sunday = 'sunday',
+}

snapshots/input/syntax/src/structural-type.ts

@@ -10,5 +10,8 @@ export function bar2(): Promise<number> {
 
 type OptionsFlags<Type> = { [Property in keyof Type]: boolean }
 type FeatureFlags = { darkMode: () => void }
+export type PropertySignature = {
+  'chat/submit': [{ text: { value: string } }]
+}
 export type FeatureOptions = OptionsFlags<FeatureFlags> // implicitly // type FeatureOptions = { // darkMode: boolean; // } const fo: FeatureOptions = { darkMode: true }; // ^ go to def
 export const fo: FeatureOptions = { darkMode: true }