diff --git a/lib/adapters/autocomplete-adapter.ts b/lib/adapters/autocomplete-adapter.ts
index aec86db9..769579f1 100644
--- a/lib/adapters/autocomplete-adapter.ts
+++ b/lib/adapters/autocomplete-adapter.ts
@@ -59,12 +59,12 @@ class PossiblyResolvedCompletionItem {
 /** Public: Adapts the language server protocol "textDocument/completion" to the Atom AutoComplete+ package. */
 export default class AutocompleteAdapter {
   public static canAdapt(serverCapabilities: ServerCapabilities): boolean {
-    return serverCapabilities.completionProvider != null
+    return serverCapabilities.completionProvider !== undefined
   }
 
   public static canResolve(serverCapabilities: ServerCapabilities): boolean {
     return (
-      serverCapabilities.completionProvider != null && serverCapabilities.completionProvider.resolveProvider === true
+      serverCapabilities.completionProvider !== undefined && serverCapabilities.completionProvider.resolveProvider === true
     )
   }
 
@@ -89,7 +89,7 @@ export default class AutocompleteAdapter {
     shouldReplace: ShouldReplace = false
   ): Promise<ac.AnySuggestion[]> {
     const triggerChars =
-      server.capabilities.completionProvider != null
+      server.capabilities.completionProvider !== undefined
         ? server.capabilities.completionProvider.triggerCharacters || []
         : []
 
@@ -233,11 +233,11 @@ export default class AutocompleteAdapter {
     const cache = this._suggestionCache.get(server)
     if (cache) {
       const possiblyResolvedCompletionItem = cache.suggestionMap.get(suggestion)
-      if (possiblyResolvedCompletionItem != null && possiblyResolvedCompletionItem.isResolved === false) {
+      if (possiblyResolvedCompletionItem !== undefined && possiblyResolvedCompletionItem.isResolved === false) {
         const resolvedCompletionItem = await server.connection.completionItemResolve(
           possiblyResolvedCompletionItem.completionItem
         )
-        if (resolvedCompletionItem != null) {
+        if (resolvedCompletionItem !== null) {
           AutocompleteAdapter.resolveSuggestion(resolvedCompletionItem, suggestion, request, onDidConvertCompletionItem)
           possiblyResolvedCompletionItem.isResolved = true
         }
@@ -254,7 +254,7 @@ export default class AutocompleteAdapter {
   ): void {
     // only the `documentation` and `detail` properties may change when resolving
     AutocompleteAdapter.applyDetailsToSuggestion(resolvedCompletionItem, suggestion)
-    if (onDidConvertCompletionItem != null) {
+    if (onDidConvertCompletionItem !== undefined) {
       onDidConvertCompletionItem(resolvedCompletionItem, suggestion as ac.AnySuggestion, request)
     }
   }
@@ -417,7 +417,7 @@ export default class AutocompleteAdapter {
       shouldReplace
     )
     AutocompleteAdapter.applySnippetToSuggestion(item, suggestion as SnippetSuggestion)
-    if (onDidConvertCompletionItem != null) {
+    if (onDidConvertCompletionItem !== undefined) {
       onDidConvertCompletionItem(item, suggestion as ac.AnySuggestion, request)
     }
 
@@ -448,7 +448,7 @@ export default class AutocompleteAdapter {
       suggestion.description = item.documentation
     }
 
-    if (item.documentation != null && typeof item.documentation === "object") {
+    if (item.documentation !== undefined && typeof item.documentation === "object") {
       // Newer format specifies the kind of documentation, assign appropriately
       if (item.documentation.kind === "markdown") {
         suggestion.descriptionMarkdown = item.documentation.value
diff --git a/lib/adapters/code-action-adapter.ts b/lib/adapters/code-action-adapter.ts
index bfbc745b..c6eadb73 100644
--- a/lib/adapters/code-action-adapter.ts
+++ b/lib/adapters/code-action-adapter.ts
@@ -40,7 +40,7 @@ export default class CodeActionAdapter {
     range: Range,
     diagnostics: atomIde.Diagnostic[]
   ): Promise<atomIde.CodeAction[]> {
-    if (linterAdapter == null) {
+    if (linterAdapter === undefined) {
       return []
     }
     assert(serverCapabilities.codeActionProvider, "Must have the textDocument/codeAction capability")
@@ -100,9 +100,9 @@ export default class CodeActionAdapter {
           // Until the Linter API provides a place to store the code,
           // there's no real way for the code actions API to give it back to us.
           const converted = Convert.atomIdeDiagnosticToLSDiagnostic(diagnostic)
-          if (diagnostic.range != null && diagnostic.text != null) {
+          if (diagnostic.text !== undefined) {
             const code = linterAdapter.getDiagnosticCode(editor, diagnostic.range, diagnostic.text)
-            if (code != null) {
+            if (code !== null) {
               converted.code = code
             }
           }
diff --git a/lib/adapters/command-execution-adapter.ts b/lib/adapters/command-execution-adapter.ts
index b6b895f7..3bca6fe9 100644
--- a/lib/adapters/command-execution-adapter.ts
+++ b/lib/adapters/command-execution-adapter.ts
@@ -7,7 +7,7 @@ export default class CommandExecutionAdapter {
   private static commandsCustomCallbacks = new Map<string, CommandCustomCallbackFunction>()
 
   public static canAdapt(serverCapabilities: ServerCapabilities): boolean {
-    return serverCapabilities.executeCommandProvider != null
+    return serverCapabilities.executeCommandProvider !== undefined
   }
 
   public static registerCustomCallbackForCommand(command: string, callback: CommandCustomCallbackFunction): void {
diff --git a/lib/adapters/datatip-adapter.ts b/lib/adapters/datatip-adapter.ts
index 5563a3b5..7107089d 100644
--- a/lib/adapters/datatip-adapter.ts
+++ b/lib/adapters/datatip-adapter.ts
@@ -33,11 +33,11 @@ export default class DatatipAdapter {
     const documentPositionParams = Convert.editorToTextDocumentPositionParams(editor, point)
 
     const hover = await connection.hover(documentPositionParams)
-    if (hover == null || DatatipAdapter.isEmptyHover(hover)) {
+    if (hover === null || DatatipAdapter.isEmptyHover(hover)) {
       return null
     }
 
-    const range = hover.range == null ? Utils.getWordAtPosition(editor, point) : Convert.lsRangeToAtomRange(hover.range)
+    const range = hover.range === undefined ? Utils.getWordAtPosition(editor, point) : Convert.lsRangeToAtomRange(hover.range)
 
     const markedStrings = (Array.isArray(hover.contents) ? hover.contents : [hover.contents]).map((str) =>
       DatatipAdapter.convertMarkedString(editor, str)
@@ -47,6 +47,7 @@ export default class DatatipAdapter {
   }
 
   private static isEmptyHover(hover: Hover): boolean {
+    // TODO hover.contents is never null!
     return (
       hover.contents == null ||
       (typeof hover.contents === "string" && hover.contents.length === 0) ||
diff --git a/lib/adapters/definition-adapter.ts b/lib/adapters/definition-adapter.ts
index d1fff442..c0934883 100644
--- a/lib/adapters/definition-adapter.ts
+++ b/lib/adapters/definition-adapter.ts
@@ -43,14 +43,14 @@ export default class DefinitionAdapter {
     const definitionLocations = DefinitionAdapter.normalizeLocations(
       await connection.gotoDefinition(documentPositionParams)
     )
-    if (definitionLocations == null || definitionLocations.length === 0) {
+    if (definitionLocations === null || definitionLocations.length === 0) {
       return null
     }
 
     let queryRange
     if (serverCapabilities.documentHighlightProvider) {
       const highlights = await connection.documentHighlight(documentPositionParams)
-      if (highlights != null && highlights.length > 0) {
+      if (highlights.length > 0) {
         queryRange = highlights.map((h) => Convert.lsRangeToAtomRange(h.range))
       }
     }
diff --git a/lib/adapters/document-sync-adapter.ts b/lib/adapters/document-sync-adapter.ts
index ae23eed3..ebd76eef 100644
--- a/lib/adapters/document-sync-adapter.ts
+++ b/lib/adapters/document-sync-adapter.ts
@@ -103,12 +103,12 @@ export default class DocumentSyncAdapter {
 
   private _handleGrammarChange(editor: TextEditor): void {
     const sync = this._editors.get(editor)
-    if (sync != null && !this._editorSelector(editor)) {
+    if (sync !== undefined && !this._editorSelector(editor)) {
       this._editors.delete(editor)
       this._disposable.remove(sync)
       sync.didClose()
       sync.dispose()
-    } else if (sync == null && this._editorSelector(editor)) {
+    } else if (sync === undefined && this._editorSelector(editor)) {
       this._handleNewEditor(editor)
     }
   }
@@ -160,10 +160,11 @@ export class TextEditorSyncAdapter {
     private _versions: Map<string, number>,
     private _reportBusyWhile: Utils.ReportBusyWhile
   ) {
+    // TODO atom.project.onDidChangeFiles is never null
     this._fakeDidChangeWatchedFiles = atom.project.onDidChangeFiles == null
 
     const changeTracking = this.setupChangeTracking(_documentSync)
-    if (changeTracking != null) {
+    if (changeTracking !== null) {
       this._disposable.add(changeTracking)
     }
 
@@ -279,7 +280,7 @@ export class TextEditorSyncAdapter {
 
   private _bumpVersion(): void {
     const filePath = this._editor.getPath()
-    if (filePath == null) {
+    if (filePath === undefined) {
       return
     }
     this._versions.set(filePath, this._getVersion(filePath) + 1)
@@ -291,7 +292,7 @@ export class TextEditorSyncAdapter {
    */
   private didOpen(): void {
     const filePath = this._editor.getPath()
-    if (filePath == null) {
+    if (filePath === undefined) {
       return
     } // Not yet saved
 
@@ -315,7 +316,7 @@ export class TextEditorSyncAdapter {
 
   /** Called when the {TextEditor} is closed and sends the 'didCloseTextDocument' notification to the connected language server. */
   public didClose(): void {
-    if (this._editor.getPath() == null) {
+    if (this._editor.getPath() === undefined) {
       return
     } // Not yet saved
 
diff --git a/lib/adapters/find-references-adapter.ts b/lib/adapters/find-references-adapter.ts
index 9742c090..d162d56f 100644
--- a/lib/adapters/find-references-adapter.ts
+++ b/lib/adapters/find-references-adapter.ts
@@ -35,10 +35,6 @@ export default class FindReferencesAdapter {
     projectRoot: string | null
   ): Promise<atomIde.FindReferencesReturn | null> {
     const locations = await connection.findReferences(FindReferencesAdapter.createReferenceParams(editor, point))
-    if (locations == null) {
-      return null
-    }
-
     const references: atomIde.Reference[] = locations.map(FindReferencesAdapter.locationToReference)
     return {
       type: "data",
diff --git a/lib/adapters/linter-push-v2-adapter.ts b/lib/adapters/linter-push-v2-adapter.ts
index bdae8217..f4e12473 100644
--- a/lib/adapters/linter-push-v2-adapter.ts
+++ b/lib/adapters/linter-push-v2-adapter.ts
@@ -118,9 +118,9 @@ export default class LinterPushV2Adapter {
    */
   public getDiagnosticCode(editor: atom.TextEditor, range: atom.Range, text: string): DiagnosticCode | null {
     const path = editor.getPath()
-    if (path != null) {
+    if (path !== undefined) {
       const diagnosticCodes = this._diagnosticCodes.get(path)
-      if (diagnosticCodes != null) {
+      if (diagnosticCodes !== undefined) {
         return diagnosticCodes.get(getCodeKey(range, text)) || null
       }
     }
diff --git a/lib/adapters/notifications-adapter.ts b/lib/adapters/notifications-adapter.ts
index 68b4f4e2..d25ee4db 100644
--- a/lib/adapters/notifications-adapter.ts
+++ b/lib/adapters/notifications-adapter.ts
@@ -42,7 +42,7 @@ export default class NotificationsAdapter {
           text: a.title,
           onDidClick: () => {
             resolve(a)
-            if (notification != null) {
+            if (notification !== null) {
               notification.dismiss()
             }
           },
@@ -51,7 +51,7 @@ export default class NotificationsAdapter {
 
       const notification = addNotificationForMessage(params.type, params.message, options)
 
-      if (notification != null) {
+      if (notification !== null) {
         notification.onDidDismiss(() => {
           resolve(null)
         })
diff --git a/lib/adapters/outline-view-adapter.ts b/lib/adapters/outline-view-adapter.ts
index 5c11a287..889cee21 100644
--- a/lib/adapters/outline-view-adapter.ts
+++ b/lib/adapters/outline-view-adapter.ts
@@ -86,7 +86,7 @@ export default class OutlineViewAdapter {
     return symbols.map((symbol) => {
       const tree = OutlineViewAdapter.hierarchicalSymbolToOutline(symbol)
 
-      if (symbol.children != null) {
+      if (symbol.children !== undefined) {
         tree.children = OutlineViewAdapter.createHierarchicalOutlineTrees(symbol.children)
       }
 
@@ -123,16 +123,16 @@ export default class OutlineViewAdapter {
     // Create a map of containers by name with all items that have that name
     const containers = allItems.reduce((map, item) => {
       const name = item.outline.representativeName
-      if (name != null) {
+      if (name !== undefined) {
         const container = map.get(name)
-        if (container == null) {
+        if (container === undefined) {
           map.set(name, [item.outline])
         } else {
           container.push(item.outline)
         }
       }
       return map
-    }, new Map())
+    }, new Map<string, atomIde.OutlineTree[]>())
 
     const roots: atomIde.OutlineTree[] = []
 
@@ -140,12 +140,12 @@ export default class OutlineViewAdapter {
     for (const item of allItems) {
       const containerName = item.containerName
       const child = item.outline
-      if (containerName == null || containerName === "") {
+      if (containerName === undefined || containerName === "") {
         roots.push(item.outline)
       } else {
         const possibleParents = containers.get(containerName)
         let closestParent = OutlineViewAdapter._getClosestParent(possibleParents, child)
-        if (closestParent == null) {
+        if (closestParent === null) {
           closestParent = {
             plainText: containerName,
             representativeName: containerName,
@@ -153,7 +153,7 @@ export default class OutlineViewAdapter {
             children: [child],
           }
           roots.push(closestParent)
-          if (possibleParents == null) {
+          if (possibleParents === undefined) {
             containers.set(containerName, [closestParent])
           } else {
             possibleParents.push(closestParent)
@@ -168,10 +168,10 @@ export default class OutlineViewAdapter {
   }
 
   private static _getClosestParent(
-    candidates: atomIde.OutlineTree[] | null,
+    candidates: atomIde.OutlineTree[] | undefined,
     child: atomIde.OutlineTree
   ): atomIde.OutlineTree | null {
-    if (candidates == null || candidates.length === 0) {
+    if (candidates === undefined || candidates.length === 0) {
       return null
     }
 
@@ -186,7 +186,7 @@ export default class OutlineViewAdapter {
         if (
           parent === undefined ||
           parent.startPosition.isLessThanOrEqual(candidate.startPosition) ||
-          (parent.endPosition != null &&
+          (parent.endPosition !== undefined &&
             candidate.endPosition &&
             parent.endPosition.isGreaterThanOrEqual(candidate.endPosition))
         ) {
@@ -215,7 +215,7 @@ export default class OutlineViewAdapter {
           value: symbol.name,
         },
       ],
-      icon: icon != null ? icon : undefined,
+      icon: icon !== null ? icon : undefined,
       representativeName: symbol.name,
       startPosition: Convert.positionToPoint(symbol.selectionRange.start),
       endPosition: Convert.positionToPoint(symbol.selectionRange.end),
@@ -238,7 +238,7 @@ export default class OutlineViewAdapter {
           value: symbol.name,
         },
       ],
-      icon: icon != null ? icon : undefined,
+      icon: icon !== null ? icon : undefined,
       representativeName: symbol.name,
       startPosition: Convert.positionToPoint(symbol.location.range.start),
       endPosition: Convert.positionToPoint(symbol.location.range.end),
diff --git a/lib/adapters/signature-help-adapter.ts b/lib/adapters/signature-help-adapter.ts
index 1c29b404..bfb0cd51 100644
--- a/lib/adapters/signature-help-adapter.ts
+++ b/lib/adapters/signature-help-adapter.ts
@@ -19,7 +19,7 @@ export default class SignatureHelpAdapter {
 
   /** @returns A {Boolean} indicating this adapter can adapt the server based on the given serverCapabilities. */
   public static canAdapt(serverCapabilities: ServerCapabilities): boolean {
-    return serverCapabilities.signatureHelpProvider != null
+    return serverCapabilities.signatureHelpProvider !== undefined
   }
 
   public dispose(): void {
@@ -28,7 +28,7 @@ export default class SignatureHelpAdapter {
 
   public attach(register: atomIde.SignatureHelpRegistry): void {
     const { signatureHelpProvider } = this._capabilities
-    assert(signatureHelpProvider != null)
+    assert(signatureHelpProvider !== undefined)
 
     let triggerCharacters: Set<string> | undefined
     if (signatureHelpProvider && Array.isArray(signatureHelpProvider.triggerCharacters)) {