diff --git a/src/__tests__/handler/codeActions.test.ts b/src/__tests__/handler/codeActions.test.ts
index 9a07f1de8a7..d299f2d1c11 100644
--- a/src/__tests__/handler/codeActions.test.ts
+++ b/src/__tests__/handler/codeActions.test.ts
@@ -323,7 +323,7 @@ describe('handler codeActions', () => {
       let edit = { changes: { [doc.uri]: edits } }
       let action = CodeAction.create('code fix', edit, CodeActionKind.QuickFix)
       currActions = [action, CodeAction.create('foo')]
-      let promise = codeActions.doCodeAction(null)
+      let promise = codeActions.doCodeAction(null, [])
       await helper.waitFloat()
       let ids = await nvim.call('coc#float#get_float_win_list') as number[]
       expect(ids.length).toBeGreaterThan(0)
@@ -398,7 +398,7 @@ describe('handler codeActions', () => {
       let spy = jest.spyOn(window, 'showQuickpick').mockImplementation(() => {
         return Promise.resolve(-1)
       })
-      await codeActions.doCodeAction(null)
+      await codeActions.doCodeAction(null, [])
       spy.mockRestore()
       helper.updateConfiguration('coc.preferences.floatActions', true)
     })
diff --git a/src/extension/manager.ts b/src/extension/manager.ts
index 1d8d2cde349..807f8313ccd 100644
--- a/src/extension/manager.ts
+++ b/src/extension/manager.ts
@@ -256,7 +256,7 @@ export class ExtensionManager {
    * Activate extension, throw error if disabled or doesn't exist.
    * Returns true if extension successfully activated.
    */
-  public async activate(id): Promise<boolean> {
+  public async activate(id: string): Promise<boolean> {
     let item = this.extensions.get(id)
     if (!item) throw new Error(`Extension ${id} not registered!`)
     let { extension } = item
@@ -265,7 +265,7 @@ export class ExtensionManager {
     return extension.isActive === true
   }
 
-  public async deactivate(id): Promise<void> {
+  public async deactivate(id: string): Promise<void> {
     let item = this.extensions.get(id)
     if (!item || !item.extension.isActive) return
     await Promise.resolve(item.deactivate())
diff --git a/src/handler/codeActions.ts b/src/handler/codeActions.ts
index 38130ae7683..a361a20070f 100644
--- a/src/handler/codeActions.ts
+++ b/src/handler/codeActions.ts
@@ -79,7 +79,7 @@ export default class CodeActions {
     return workspace.initialConfiguration.get<boolean>('coc.preferences.floatActions', true)
   }
 
-  public async doCodeAction(mode: string | null, only?: CodeActionKind[] | string, showDisable = false): Promise<void> {
+  public async doCodeAction(mode: string | null, only: CodeActionKind[] | string, showDisable = false): Promise<void> {
     let { doc } = await this.handler.getCurrentState()
     let range: Range | undefined
     if (mode) range = await window.getSelectedRange(mode)
diff --git a/src/handler/hover.ts b/src/handler/hover.ts
index 9b8c346d39d..91449d0bed6 100644
--- a/src/handler/hover.ts
+++ b/src/handler/hover.ts
@@ -17,8 +17,7 @@ import { characterIndex } from '../util/string'
 import window from '../window'
 import workspace from '../workspace'
 import { HandlerDelegate } from './types'
-
-export type HoverTarget = 'float' | 'preview' | 'echo'
+import { HoverTarget } from '../plugin'
 
 interface HoverConfig {
   target: HoverTarget
diff --git a/src/plugin.ts b/src/plugin.ts
index 63ab737126b..2b006026ae8 100644
--- a/src/plugin.ts
+++ b/src/plugin.ts
@@ -1,6 +1,6 @@
 'use strict'
 import { Neovim } from './neovim'
-import { CodeActionKind, InsertTextMode, Range } from 'vscode-languageserver-types'
+import { CallHierarchyItem, CodeAction, CodeActionKind, InsertTextMode, Range, WorkspaceSymbol } from 'vscode-languageserver-types'
 import commandManager from './commands'
 import completion, { Completion } from './completion'
 import sources from './completion/sources'
@@ -19,6 +19,8 @@ import window from './window'
 import workspace, { Workspace } from './workspace'
 const logger = createLogger('plugin')
 
+export type HoverTarget = 'float' | 'preview' | 'echo'
+
 export default class Plugin {
   private ready = false
   private initialized = false
@@ -58,7 +60,7 @@ export default class Plugin {
     this.addAction('openLog', () => this.handler.workspace.openLog())
     this.addAction('attach', () => workspace.attach())
     this.addAction('detach', () => workspace.detach())
-    this.addAction('doKeymap', (key, defaultReturn) => this.handler.workspace.doKeymap(key, defaultReturn))
+    this.addAction('doKeymap', (key: string, defaultReturn: string) => this.handler.workspace.doKeymap(key, defaultReturn))
     this.addAction('registerExtensions', (...folders: string[]) => extensions.manager.loadExtension(folders), 'registExtensions')
     this.addAction('snippetCheck', (checkExpand: boolean, checkJump: boolean) => this.handler.workspace.snippetCheck(checkExpand, checkJump))
     this.addAction('snippetInsert', (range: Range, newText: string, mode?: InsertTextMode, ultisnip?: UltiSnippetOption) => snippetManager.insertSnippet(newText, true, range, mode, ultisnip, true))
@@ -76,7 +78,7 @@ export default class Plugin {
     this.addAction('openList', (...args: string[]) => listManager.start(args))
     this.addAction('listNames', () => listManager.names)
     this.addAction('listDescriptions', () => listManager.descriptions)
-    this.addAction('listLoadItems', name => listManager.loadItems(name))
+    this.addAction('listLoadItems', (name: string) => listManager.loadItems(name))
     this.addAction('listResume', (name?: string) => listManager.resume(name))
     this.addAction('listCancel', () => listManager.cancel(true))
     this.addAction('listPrev', (name?: string) => listManager.previous(name))
@@ -93,58 +95,58 @@ export default class Plugin {
     this.addAction('colorPresentation', () => this.handler.colors.pickPresentation())
     this.addAction('highlight', () => this.handler.documentHighlighter.highlight())
     this.addAction('fold', (kind?: string) => this.handler.fold.fold(kind))
-    this.addAction('startCompletion', option => completion.startCompletion(option))
+    this.addAction('startCompletion', (option: { source?: string }) => completion.startCompletion(option))
     this.addAction('sourceStat', () => sources.sourceStats())
-    this.addAction('refreshSource', name => sources.refresh(name))
-    this.addAction('toggleSource', name => sources.toggleSource(name))
-    this.addAction('diagnosticRefresh', bufnr => diagnosticManager.refresh(bufnr))
-    this.addAction('diagnosticInfo', target => diagnosticManager.echoCurrentMessage(target))
-    this.addAction('diagnosticToggle', enable => diagnosticManager.toggleDiagnostic(enable))
-    this.addAction('diagnosticToggleBuffer', (bufnr, enable) => diagnosticManager.toggleDiagnosticBuffer(bufnr, enable))
-    this.addAction('diagnosticNext', severity => diagnosticManager.jumpNext(severity))
-    this.addAction('diagnosticPrevious', severity => diagnosticManager.jumpPrevious(severity))
+    this.addAction('refreshSource', (name: string) => sources.refresh(name))
+    this.addAction('toggleSource', (name: string) => sources.toggleSource(name))
+    this.addAction('diagnosticRefresh', (bufnr?: number) => diagnosticManager.refresh(bufnr))
+    this.addAction('diagnosticInfo', (target?: string) => diagnosticManager.echoCurrentMessage(target))
+    this.addAction('diagnosticToggle', (enable?: number) => diagnosticManager.toggleDiagnostic(enable))
+    this.addAction('diagnosticToggleBuffer', (bufnr?: number, enable?: number) => diagnosticManager.toggleDiagnosticBuffer(bufnr, enable))
+    this.addAction('diagnosticNext', (severity?: string) => diagnosticManager.jumpNext(severity))
+    this.addAction('diagnosticPrevious', (severity?: string) => diagnosticManager.jumpPrevious(severity))
     this.addAction('diagnosticPreview', () => diagnosticManager.preview())
     this.addAction('diagnosticList', () => diagnosticManager.getDiagnosticList())
     this.addAction('diagnosticRelatedInformation', () => diagnosticManager.relatedInformation())
-    this.addAction('findLocations', (id, method, params, openCommand) => this.handler.locations.findLocations(id, method, params, openCommand))
+    this.addAction('findLocations', (id: string, method: string, params: any, openCommand: string) => this.handler.locations.findLocations(id, method, params, openCommand))
     this.addAction('getTagList', () => this.handler.locations.getTagList())
     this.addAction('definitions', () => this.handler.locations.definitions())
     this.addAction('declarations', () => this.handler.locations.declarations())
     this.addAction('implementations', () => this.handler.locations.implementations())
     this.addAction('typeDefinitions', () => this.handler.locations.typeDefinitions())
-    this.addAction('references', excludeDeclaration => this.handler.locations.references(excludeDeclaration))
-    this.addAction('jumpUsed', openCommand => this.handler.locations.gotoReferences(openCommand, false))
-    this.addAction('jumpDefinition', openCommand => this.handler.locations.gotoDefinition(openCommand))
-    this.addAction('jumpReferences', openCommand => this.handler.locations.gotoReferences(openCommand))
-    this.addAction('jumpTypeDefinition', openCommand => this.handler.locations.gotoTypeDefinition(openCommand))
-    this.addAction('jumpDeclaration', openCommand => this.handler.locations.gotoDeclaration(openCommand))
-    this.addAction('jumpImplementation', openCommand => this.handler.locations.gotoImplementation(openCommand))
-    this.addAction('doHover', hoverTarget => this.handler.hover.onHover(hoverTarget))
-    this.addAction('definitionHover', hoverTarget => this.handler.hover.definitionHover(hoverTarget))
-    this.addAction('getHover', loc => this.handler.hover.getHover(loc))
+    this.addAction('references', (excludeDeclaration?: boolean) => this.handler.locations.references(excludeDeclaration))
+    this.addAction('jumpUsed', (openCommand?: string) => this.handler.locations.gotoReferences(openCommand, false))
+    this.addAction('jumpDefinition', (openCommand?: string | false) => this.handler.locations.gotoDefinition(openCommand))
+    this.addAction('jumpReferences', (openCommand?: string | false) => this.handler.locations.gotoReferences(openCommand))
+    this.addAction('jumpTypeDefinition', (openCommand?: string | false) => this.handler.locations.gotoTypeDefinition(openCommand))
+    this.addAction('jumpDeclaration', (openCommand?: string | false) => this.handler.locations.gotoDeclaration(openCommand))
+    this.addAction('jumpImplementation', (openCommand?: string | false) => this.handler.locations.gotoImplementation(openCommand))
+    this.addAction('doHover', (hoverTarget: HoverTarget) => this.handler.hover.onHover(hoverTarget))
+    this.addAction('definitionHover', (hoverTarget: HoverTarget) => this.handler.hover.definitionHover(hoverTarget))
+    this.addAction('getHover', (loc?: { bufnr?: number, line: number, col: number }) => this.handler.hover.getHover(loc))
     this.addAction('showSignatureHelp', () => this.handler.signature.triggerSignatureHelp())
     this.addAction('documentSymbols', (bufnr?: number) => this.handler.symbols.getDocumentSymbols(bufnr))
     this.addAction('symbolRanges', () => this.handler.documentHighlighter.getSymbolsRanges())
     this.addAction('selectionRanges', () => this.handler.selectionRange.getSelectionRanges())
-    this.addAction('rangeSelect', (visualmode, forward) => this.handler.selectionRange.selectRange(visualmode, forward))
-    this.addAction('rename', newName => this.handler.rename.rename(newName))
-    this.addAction('getWorkspaceSymbols', input => this.handler.symbols.getWorkspaceSymbols(input))
-    this.addAction('resolveWorkspaceSymbol', symbolInfo => this.handler.symbols.resolveWorkspaceSymbol(symbolInfo))
-    this.addAction('formatSelected', mode => this.handler.format.formatCurrentRange(mode))
+    this.addAction('rangeSelect', (visualmode: string, forward: boolean) => this.handler.selectionRange.selectRange(visualmode, forward))
+    this.addAction('rename', (newName?: string) => this.handler.rename.rename(newName))
+    this.addAction('getWorkspaceSymbols', (input: string) => this.handler.symbols.getWorkspaceSymbols(input))
+    this.addAction('resolveWorkspaceSymbol', (symbolInfo: WorkspaceSymbol) => this.handler.symbols.resolveWorkspaceSymbol(symbolInfo))
+    this.addAction('formatSelected', (mode: string) => this.handler.format.formatCurrentRange(mode))
     this.addAction('format', () => this.handler.format.formatCurrentBuffer())
     this.addAction('commands', () => commandManager.commandList)
     this.addAction('services', () => services.getServiceStats())
-    this.addAction('toggleService', name => services.toggle(name))
-    this.addAction('codeAction', (mode, only, noExclude) => this.handler.codeActions.doCodeAction(mode, only, noExclude))
+    this.addAction('toggleService', (name: string) => services.toggle(name))
+    this.addAction('codeAction', (mode: string | null, only: CodeActionKind[] | string, noExclude: boolean) => this.handler.codeActions.doCodeAction(mode, only, noExclude))
     this.addAction('organizeImport', () => this.handler.codeActions.organizeImport())
     this.addAction('fixAll', () => this.handler.codeActions.doCodeAction(null, [CodeActionKind.SourceFixAll]))
-    this.addAction('doCodeAction', codeAction => this.handler.codeActions.applyCodeAction(codeAction))
-    this.addAction('codeActions', (mode, only) => this.handler.codeActions.getCurrentCodeActions(mode, only))
-    this.addAction('quickfixes', mode => this.handler.codeActions.getCurrentCodeActions(mode, [CodeActionKind.QuickFix]))
+    this.addAction('doCodeAction', (codeAction: CodeAction) => this.handler.codeActions.applyCodeAction(codeAction))
+    this.addAction('codeActions', (mode?: string, only?: CodeActionKind[]) => this.handler.codeActions.getCurrentCodeActions(mode, only))
+    this.addAction('quickfixes', (mode?: string) => this.handler.codeActions.getCurrentCodeActions(mode, [CodeActionKind.QuickFix]))
     this.addAction('codeLensAction', () => this.handler.codeLens.doAction())
     this.addAction('doQuickfix', () => this.handler.codeActions.doQuickfix())
     this.addAction('search', (...args: string[]) => this.handler.refactor.search(args))
-    this.addAction('saveRefactor', bufnr => this.handler.refactor.save(bufnr))
+    this.addAction('saveRefactor', (bufnr: number) => this.handler.refactor.save(bufnr))
     this.addAction('refactor', () => this.handler.refactor.doRefactor())
     this.addAction('runCommand', (...args: any[]) => this.handler.commands.runCommand(...args))
     this.addAction('repeatCommand', () => this.handler.commands.repeat())
@@ -153,22 +155,22 @@ export default class Plugin {
     this.addAction('extensionStats', () => extensions.getExtensionStates())
     this.addAction('loadedExtensions', () => extensions.manager.loadedExtensions)
     this.addAction('watchExtension', (id: string) => extensions.manager.watchExtension(id))
-    this.addAction('activeExtension', name => extensions.manager.activate(name))
-    this.addAction('deactivateExtension', name => extensions.manager.deactivate(name))
-    this.addAction('reloadExtension', name => extensions.manager.reloadExtension(name))
-    this.addAction('toggleExtension', name => extensions.manager.toggleExtension(name))
+    this.addAction('activeExtension', (name: string) => extensions.manager.activate(name))
+    this.addAction('deactivateExtension', (name: string) => extensions.manager.deactivate(name))
+    this.addAction('reloadExtension', (name: string) => extensions.manager.reloadExtension(name))
+    this.addAction('toggleExtension', (name: string) => extensions.manager.toggleExtension(name))
     this.addAction('uninstallExtension', (...args: string[]) => extensions.manager.uninstallExtensions(args))
     this.addAction('getCurrentFunctionSymbol', () => this.handler.symbols.getCurrentFunctionSymbol())
     this.addAction('showOutline', (keep?: number) => this.handler.symbols.showOutline(keep))
     this.addAction('hideOutline', () => this.handler.symbols.hideOutline())
     this.addAction('getWordEdit', () => this.handler.rename.getWordEdit())
-    this.addAction('addCommand', cmd => this.handler.commands.addVimCommand(cmd))
-    this.addAction('addRanges', ranges => this.cursors.addRanges(ranges))
+    this.addAction('addCommand', (cmd: { id: string, cmd: string, title?: string }) => this.handler.commands.addVimCommand(cmd))
+    this.addAction('addRanges', (ranges: Range[]) => this.cursors.addRanges(ranges))
     this.addAction('currentWorkspacePath', () => workspace.rootPath)
-    this.addAction('selectCurrentPlaceholder', triggerAutocmd => snippetManager.selectCurrentPlaceholder(!!triggerAutocmd))
-    this.addAction('codeActionRange', (start, end, only) => this.handler.codeActions.codeActionRange(start, end, only))
-    this.addAction('incomingCalls', item => this.handler.callHierarchy.getIncoming(item))
-    this.addAction('outgoingCalls', item => this.handler.callHierarchy.getOutgoing(item))
+    this.addAction('selectCurrentPlaceholder', (triggerAutocmd: boolean) => snippetManager.selectCurrentPlaceholder(!!triggerAutocmd))
+    this.addAction('codeActionRange', (start: number, end: number, only?: string) => this.handler.codeActions.codeActionRange(start, end, only))
+    this.addAction('incomingCalls', (item?: CallHierarchyItem) => this.handler.callHierarchy.getIncoming(item))
+    this.addAction('outgoingCalls', (item?: CallHierarchyItem) => this.handler.callHierarchy.getOutgoing(item))
     this.addAction('showIncomingCalls', () => this.handler.callHierarchy.showCallHierarchyTree('incoming'))
     this.addAction('showOutgoingCalls', () => this.handler.callHierarchy.showCallHierarchyTree('outgoing'))
     this.addAction('showSuperTypes', () => this.handler.typeHierarchy.showTypeHierarchyTree('supertypes'))