diff --git a/lib/misc/blocks.js b/lib/misc/blocks.js
index 46417203..86bd7f67 100644
--- a/lib/misc/blocks.js
+++ b/lib/misc/blocks.js
@@ -1,16 +1,39 @@
 'use babel'
 // TODO: docstrings
+// TODO: Fix RangeCompatible types
 
 import { forLines } from './scopes'
+/**
+ * interface LineInfo {
+ * scope: readonly string[]
+ * line: string
+ * }
+ */
 
-export function getLine (ed, l) {
+
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {number} l
+ * @returns {LineInfo}
+ */
+export function getLine(editor, l) {
   return {
-    scope: ed.scopeDescriptorForBufferPosition([l, 0]).scopes,
-    line: ed.getTextInBufferRange([[l, 0], [l, Infinity]])
+    scope: editor.scopeDescriptorForBufferPosition([l, 0]).getScopesArray(),
+    line: editor.getTextInBufferRange([
+      [l, 0],
+      [l, Infinity],
+    ]),
   }
 }
 
-function isBlank ({line, scope}, allowDocstrings = false) {
+/**
+ *
+ * @param {LineInfo.line} line
+ * @param {LineInfo.scope} scope
+ * @param {boolean} allowDocstrings
+ */
+function isBlank({ line, scope }, allowDocstrings = false) {
   for (const s of scope) {
     if (/\bcomment\b/.test(s) || (!allowDocstrings && /\bdocstring\b/.test(s))) {
       return true
@@ -18,43 +41,70 @@ function isBlank ({line, scope}, allowDocstrings = false) {
   }
   return /^\s*(#.*)?$/.test(line)
 }
-function isEnd ({ line, scope }) {
-  if (isStringEnd({ line, scope })) {
+
+/**
+ *
+ * @param {LineInfo} lineInfo
+ */
+function isEnd(lineInfo) {
+  if (isStringEnd(lineInfo)) {
     return true
   }
-  return /^(end\b|\)|\]|\})/.test(line)
+  return /^(end\b|\)|]|})/.test(lineInfo.line)
 }
-function isStringEnd ({ line, scope }) {
-  scope = scope.join(' ')
-  return /\bstring\.multiline\.end\b/.test(scope) ||
-        (/\bstring\.end\b/.test(scope) && /\bbacktick\b/.test(scope))
+
+/**
+ *
+ * @param {LineInfo} lineInfo
+ */
+function isStringEnd(lineInfo) {
+  const scope = lineInfo.scope.join(' ')
+  return /\bstring\.multiline\.end\b/.test(scope) || (/\bstring\.end\b/.test(scope) && /\bbacktick\b/.test(scope))
 }
-function isCont ({ line, scope }) {
-  scope = scope.join(' ')
-  if (/\bstring\b/.test(scope) && !(/\bpunctuation\.definition\.string\b/.test(scope))) {
+
+/**
+ *
+ * @param {LineInfo} lineInfo
+ */
+function isCont(lineInfo) {
+  const scope = lineInfo.scope.join(' ')
+  if (/\bstring\b/.test(scope) && !/\bpunctuation\.definition\.string\b/.test(scope)) {
     return true
   }
-
-  return line.match(/^(else|elseif|catch|finally)\b/)
+  return lineInfo.line.match(/^(else|elseif|catch|finally)\b/)
 }
-function isStart (lineInfo) {
+
+/**
+ *
+ * @param {LineInfo} lineInfo
+ */
+function isStart(lineInfo) {
   return !(/^\s/.test(lineInfo.line) || isBlank(lineInfo) || isEnd(lineInfo) || isCont(lineInfo))
 }
 
-function walkBack(ed, row) {
-  while ((row > 0) && !isStart(getLine(ed, row))) {
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {number} row
+ */
+function walkBack(editor, row) {
+  while (row > 0 && !isStart(getLine(editor, row))) {
     row--
   }
   return row
 }
 
-function walkForward (ed, start) {
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {number} start
+ */
+function walkForward(editor, start) {
   let end = start
   let mark = start
-  while (mark < ed.getLastBufferRow()) {
+  while (mark < editor.getLastBufferRow()) {
     mark++
-    const lineInfo = getLine(ed, mark)
-
+    const lineInfo = getLine(editor, mark)
     if (isStart(lineInfo)) {
       break
     }
@@ -62,10 +112,7 @@ function walkForward (ed, start) {
       // An `end` only counts when  there still are unclosed blocks (indicated by `forLines`
       // returning a non-empty array).
       // If the line closes a multiline string we also take that as ending the block.
-      if (
-            !(forLines(ed, start, mark-1).length === 0) ||
-            isStringEnd(lineInfo)
-         ) {
+      if (!(forLines(editor, start, mark - 1).length === 0) || isStringEnd(lineInfo)) {
         end = mark
       }
     } else if (!(isBlank(lineInfo) || isStart(lineInfo))) {
@@ -75,74 +122,119 @@ function walkForward (ed, start) {
   return end
 }
 
-function getRange (ed, row) {
-  const start = walkBack(ed, row)
-  const end = walkForward(ed, start)
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {number} row
+ * @returns {[[number, number], [number, number]] | undefined}
+ */
+function getRange(editor, row) {
+  const start = walkBack(editor, row)
+  const end = walkForward(editor, start)
   if (start <= row && row <= end) {
-    return [[start, 0], [end, Infinity]]
+    return [
+      [start, 0],
+      [end, Infinity],
+    ]
+  } else {
+    return undefined // TODO: make sure returned range from getRanges is not undefined
   }
 }
 
-function getSelection (ed, sel) {
-  const {start, end} = sel.getBufferRange()
-  const range = [[start.row, start.column], [end.row, end.column]]
-  while (isBlank(getLine(ed, range[0][0]), true) && (range[0][0] <= range[1][0])) {
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {Selection} selection
+ */
+function getSelection(editor, selection) {
+  const { start, end } = selection.getBufferRange()
+  const range = [
+    [start.row, start.column],
+    [end.row, end.column],
+  ]
+  while (isBlank(getLine(editor, range[0][0]), true) && range[0][0] <= range[1][0]) {
     range[0][0]++
     range[0][1] = 0
   }
-  while (isBlank(getLine(ed, range[1][0]), true) && (range[1][0] >= range[0][0])) {
+  while (isBlank(getLine(editor, range[1][0]), true) && range[1][0] >= range[0][0]) {
     range[1][0]--
     range[1][1] = Infinity
   }
   return range
 }
 
-export function moveNext (ed, sel, range) {
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {Selection} selection
+ * @param {[[number, number], [number, number]]} range
+ */
+export function moveNext(editor, selection, range) {
   // Ensure enough room at the end of the buffer
   const row = range[1][0]
   let last
-  while ((last = ed.getLastBufferRow()) < (row+2)) {
-    if ((last !== row) && !isBlank(getLine(ed, last))) {
+  while ((last = editor.getLastBufferRow()) < row + 2) {
+    if (last !== row && !isBlank(getLine(editor, last))) {
       break
     }
-    sel.setBufferRange([[last, Infinity], [last, Infinity]])
-    sel.insertText('\n')
+    selection.setBufferRange([
+      [last, Infinity],
+      [last, Infinity],
+    ])
+    selection.insertText('\n')
   }
   // Move the cursor
   let to = row + 1
-  while ((to < ed.getLastBufferRow()) && isBlank(getLine(ed, to))) {
+  while (to < editor.getLastBufferRow() && isBlank(getLine(editor, to))) {
     to++
   }
-  to = walkForward(ed, to)
-  return sel.setBufferRange([[to, Infinity], [to, Infinity]])
+  to = walkForward(editor, to)
+  return selection.setBufferRange([
+    [to, Infinity],
+    [to, Infinity],
+  ])
 }
 
-function getRanges (ed) {
-  const ranges = ed.getSelections().map(sel => {
+/**
+ *
+ * @param {TextEditor} editor
+ */
+function getRanges(editor) {
+  const ranges = editor.getSelections().map((selection) => {
     return {
-      selection: sel,
-      range: sel.isEmpty() ?
-        getRange(ed, sel.getHeadBufferPosition().row) :
-        getSelection(ed, sel)
+      selection: selection,
+      range: selection.isEmpty()
+        ? getRange(editor, selection.getHeadBufferPosition().row)
+        : getSelection(editor, selection),
     }
+    // TODO: replace with getBufferRowRange? (getHeadBufferPosition isn't a public API)
   })
   return ranges.filter(({ range }) => {
-    return range && ed.getTextInBufferRange(range).trim()
+    return range && editor.getTextInBufferRange(range).trim()
   })
 }
 
-export function get (ed) {
-  return getRanges(ed).map(({ range, selection }) => {
+/**
+ *
+ * @param {TextEditor} editor
+ */
+export function get(editor) {
+  return getRanges(editor).map(({ range, selection }) => {
     return {
       range,
       selection,
       line: range[0][0],
-      text: ed.getTextInBufferRange(range)
+      text: editor.getTextInBufferRange(range),
     }
   })
 }
 
-export function getLocalContext (editor, row) {
+/**
+ *
+ * @param {TextEditor} editor
+ * @param {number} row
+ */
+export function getLocalContext(editor, row) {
   const range = getRange(editor, row)
   const context = range ? editor.getTextInBufferRange(range) : ''
   // NOTE:
@@ -152,16 +244,21 @@ export function getLocalContext (editor, row) {
   const startRow = range ? range[0][0] : 0
   return {
     context,
-    startRow
+    startRow,
   }
 }
 
-export function select (ed = atom.workspace.getActiveTextEditor()) {
-  if (!ed) return
-  return ed.mutateSelectedText(selection => {
-    const range = getRange(ed, selection.getHeadBufferPosition().row)
+/**
+ *
+ * @param {TextEditor | undefined} editor
+ */
+export function select(editor = atom.workspace.getActiveTextEditor()) {
+  if (!editor) return
+  return editor.mutateSelectedText((selection) => {
+    const range = getRange(editor, selection.getHeadBufferPosition().row)
     if (range) {
       selection.setBufferRange(range)
     }
   })
+  // TODO: replace with getBufferRowRange? (getHeadBufferPosition isn't a public API)
 }