diff --git a/src/ol/PluggableMap.js b/src/ol/PluggableMap.js
index 9232f5cb7d..f5f3a6c37f 100644
--- a/src/ol/PluggableMap.js
+++ b/src/ol/PluggableMap.js
@@ -321,7 +321,7 @@ const PluggableMap = function(options) {
 
   /**
    * @private
-   * @type {Array.<module:ol/types~PostRenderFunction>}
+   * @type {!Array.<module:ol/types~PostRenderFunction>}
    */
   this.postRenderFunctions_ = [];
 
@@ -1232,8 +1232,7 @@ PluggableMap.prototype.renderFrame_ = function(time) {
     if (frameState.animate) {
       this.render();
     }
-    Array.prototype.push.apply(
-      this.postRenderFunctions_, frameState.postRenderFunctions);
+    Array.prototype.push.apply(this.postRenderFunctions_, frameState.postRenderFunctions);
 
     if (previousFrameState) {
       const moveStart = !this.previousExtent_ ||
diff --git a/src/ol/TileCache.js b/src/ol/TileCache.js
index 7ee1f22250..4c9ef844c4 100644
--- a/src/ol/TileCache.js
+++ b/src/ol/TileCache.js
@@ -21,13 +21,12 @@ inherits(TileCache, LRUCache);
 
 
 /**
- * @param {Object.<string, ol.TileRange>} usedTiles Used tiles.
+ * @param {!Object.<string, ol.TileRange>} usedTiles Used tiles.
  */
 TileCache.prototype.expireCache = function(usedTiles) {
-  let tile, zKey;
   while (this.canExpireCache()) {
-    tile = this.peekLast();
-    zKey = tile.tileCoord[0].toString();
+    const tile = this.peekLast();
+    const zKey = tile.tileCoord[0].toString();
     if (zKey in usedTiles && usedTiles[zKey].contains(tile.tileCoord)) {
       break;
     } else {
diff --git a/src/ol/VectorImageTile.js b/src/ol/VectorImageTile.js
index 6a57370d1e..053beecdab 100644
--- a/src/ol/VectorImageTile.js
+++ b/src/ol/VectorImageTile.js
@@ -40,7 +40,7 @@ const VectorImageTile = function(tileCoord, state, sourceRevision, format,
 
   /**
    * @private
-   * @type {Object.<string, CanvasRenderingContext2D>}
+   * @type {!Object.<string, CanvasRenderingContext2D>}
    */
   this.context_ = {};
 
@@ -52,7 +52,7 @@ const VectorImageTile = function(tileCoord, state, sourceRevision, format,
 
   /**
    * @private
-   * @type {Object.<string, ol.TileReplayState>}
+   * @type {!Object.<string, ol.TileReplayState>}
    */
   this.replayState_ = {};
 
diff --git a/src/ol/array.js b/src/ol/array.js
index 6ccb81c310..99b5a7a9af 100644
--- a/src/ol/array.js
+++ b/src/ol/array.js
@@ -126,15 +126,13 @@ export function reverseSubArray(arr, begin, end) {
 
 /**
  * @param {Array.<VALUE>} arr The array to modify.
- * @param {Array.<VALUE>|VALUE} data The elements or arrays of elements
- *     to add to arr.
+ * @param {!Array.<VALUE>|VALUE} data The elements or arrays of elements to add to arr.
  * @template VALUE
  */
 export function extend(arr, data) {
-  let i;
   const extension = Array.isArray(data) ? data : [data];
   const length = extension.length;
-  for (i = 0; i < length; i++) {
+  for (let i = 0; i < length; i++) {
     arr[arr.length] = extension[i];
   }
 }
@@ -160,7 +158,7 @@ export function remove(arr, obj) {
  * @param {Array.<VALUE>} arr The array to search in.
  * @param {function(VALUE, number, ?) : boolean} func The function to compare.
  * @template VALUE
- * @return {VALUE} The element found.
+ * @return {VALUE|null} The element found or null.
  */
 export function find(arr, func) {
   const length = arr.length >>> 0;
diff --git a/src/ol/control/Attribution.js b/src/ol/control/Attribution.js
index a6633d8ba3..6d7347badc 100644
--- a/src/ol/control/Attribution.js
+++ b/src/ol/control/Attribution.js
@@ -130,7 +130,7 @@ inherits(Attribution, Control);
 Attribution.prototype.getSourceAttributions_ = function(frameState) {
   /**
    * Used to determine if an attribution already exists.
-   * @type {Object.<string, boolean>}
+   * @type {!Object.<string, boolean>}
    */
   const lookup = {};
 
diff --git a/src/ol/format/GPX.js b/src/ol/format/GPX.js
index 23e670a1a5..d674b21e5a 100644
--- a/src/ol/format/GPX.js
+++ b/src/ol/format/GPX.js
@@ -379,7 +379,7 @@ const GPX_SERIALIZERS = makeStructureNS(
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {ol.LayoutOptions} layoutOptions Layout options.
  * @param {Node} node Node.
- * @param {Object} values Values.
+ * @param {!Object} values Values.
  * @return {Array.<number>} Flat coordinates.
  */
 function appendCoordinate(flatCoordinates, layoutOptions, node, values) {
@@ -477,14 +477,11 @@ function parseExtensions(node, objectStack) {
  * @param {Array.<*>} objectStack Object stack.
  */
 function parseRtePt(node, objectStack) {
-  const values = pushParseAndPop(
-    {}, RTEPT_PARSERS, node, objectStack);
+  const values = pushParseAndPop({}, RTEPT_PARSERS, node, objectStack);
   if (values) {
-    const rteValues = /** @type {Object} */ (objectStack[objectStack.length - 1]);
-    const flatCoordinates = /** @type {Array.<number>} */
-        (rteValues['flatCoordinates']);
-    const layoutOptions = /** @type {ol.LayoutOptions} */
-        (rteValues['layoutOptions']);
+    const rteValues = /** @type {!Object} */ (objectStack[objectStack.length - 1]);
+    const flatCoordinates = /** @type {Array.<number>} */ (rteValues['flatCoordinates']);
+    const layoutOptions = /** @type {ol.LayoutOptions} */ (rteValues['layoutOptions']);
     appendCoordinate(flatCoordinates, layoutOptions, node, values);
   }
 }
@@ -497,11 +494,9 @@ function parseRtePt(node, objectStack) {
 function parseTrkPt(node, objectStack) {
   const values = pushParseAndPop({}, TRKPT_PARSERS, node, objectStack);
   if (values) {
-    const trkValues = /** @type {Object} */ (objectStack[objectStack.length - 1]);
-    const flatCoordinates = /** @type {Array.<number>} */
-        (trkValues['flatCoordinates']);
-    const layoutOptions = /** @type {ol.LayoutOptions} */
-        (trkValues['layoutOptions']);
+    const trkValues = /** @type {!Object} */ (objectStack[objectStack.length - 1]);
+    const flatCoordinates = /** @type {Array.<number>} */ (trkValues['flatCoordinates']);
+    const layoutOptions = /** @type {ol.LayoutOptions} */ (trkValues['layoutOptions']);
     appendCoordinate(flatCoordinates, layoutOptions, node, values);
   }
 }
diff --git a/src/ol/format/KML.js b/src/ol/format/KML.js
index fddeb78adf..14c357e1ac 100644
--- a/src/ol/format/KML.js
+++ b/src/ol/format/KML.js
@@ -277,7 +277,7 @@ const KML = function(opt_options) {
 
   /**
    * @private
-   * @type {Object.<string, (Array.<ol.style.Style>|string)>}
+   * @type {!Object.<string, (Array.<ol.style.Style>|string)>}
    */
   this.sharedStyles_ = {};
 
@@ -384,14 +384,11 @@ function createNameStyleFunction(foundStyle, name) {
  * @param {Array.<ol.style.Style>|undefined} style Style.
  * @param {string} styleUrl Style URL.
  * @param {Array.<ol.style.Style>} defaultStyle Default style.
- * @param {Object.<string, (Array.<ol.style.Style>|string)>} sharedStyles Shared
- *          styles.
- * @param {boolean|undefined} showPointNames true to show names for point
- *          placemarks.
+ * @param {!Object.<string, (Array.<ol.style.Style>|string)>} sharedStyles Shared styles.
+ * @param {boolean|undefined} showPointNames true to show names for point placemarks.
  * @return {ol.StyleFunction} Feature style function.
  */
-function createFeatureStyleFunction(style, styleUrl,
-  defaultStyle, sharedStyles, showPointNames) {
+function createFeatureStyleFunction(style, styleUrl, defaultStyle, sharedStyles, showPointNames) {
 
   return (
     /**
@@ -418,25 +415,21 @@ function createFeatureStyleFunction(style, styleUrl,
 
       if (style) {
         if (drawName) {
-          nameStyle = createNameStyleFunction(style[0],
-            name);
+          nameStyle = createNameStyleFunction(style[0], name);
           return style.concat(nameStyle);
         }
         return style;
       }
       if (styleUrl) {
-        const foundStyle = findStyle(styleUrl, defaultStyle,
-          sharedStyles);
+        const foundStyle = findStyle(styleUrl, defaultStyle, sharedStyles);
         if (drawName) {
-          nameStyle = createNameStyleFunction(foundStyle[0],
-            name);
+          nameStyle = createNameStyleFunction(foundStyle[0], name);
           return foundStyle.concat(nameStyle);
         }
         return foundStyle;
       }
       if (drawName) {
-        nameStyle = createNameStyleFunction(defaultStyle[0],
-          name);
+        nameStyle = createNameStyleFunction(defaultStyle[0], name);
         return defaultStyle.concat(nameStyle);
       }
       return defaultStyle;
@@ -448,7 +441,7 @@ function createFeatureStyleFunction(style, styleUrl,
 /**
  * @param {Array.<ol.style.Style>|string|undefined} styleValue Style value.
  * @param {Array.<ol.style.Style>} defaultStyle Default style.
- * @param {Object.<string, (Array.<ol.style.Style>|string)>} sharedStyles
+ * @param {!Object.<string, (Array.<ol.style.Style>|string)>} sharedStyles
  * Shared styles.
  * @return {Array.<ol.style.Style>} Style.
  */
@@ -462,8 +455,7 @@ function findStyle(styleValue, defaultStyle, sharedStyles) {
     if (!(styleValue in sharedStyles) && ('#' + styleValue in sharedStyles)) {
       styleValue = '#' + styleValue;
     }
-    return findStyle(
-      sharedStyles[styleValue], defaultStyle, sharedStyles);
+    return findStyle(sharedStyles[styleValue], defaultStyle, sharedStyles);
   } else {
     return defaultStyle;
   }
diff --git a/src/ol/format/WMSCapabilities.js b/src/ol/format/WMSCapabilities.js
index 723dbcfc13..0b9fcfccd1 100644
--- a/src/ol/format/WMSCapabilities.js
+++ b/src/ol/format/WMSCapabilities.js
@@ -446,8 +446,7 @@ function readCapabilityLayer(node, objectStack) {
  * @return {Object|undefined} Layer object.
  */
 function readLayer(node, objectStack) {
-  const parentLayerObject = /**  @type {Object.<string,*>} */
-        (objectStack[objectStack.length - 1]);
+  const parentLayerObject = /**  @type {!Object.<string,*>} */ (objectStack[objectStack.length - 1]);
 
   const layerObject = pushParseAndPop({}, LAYER_PARSERS, node, objectStack);
 
diff --git a/src/ol/geom/flat/geodesic.js b/src/ol/geom/flat/geodesic.js
index 3b6c5c0dee..9a76ffa784 100644
--- a/src/ol/geom/flat/geodesic.js
+++ b/src/ol/geom/flat/geodesic.js
@@ -32,7 +32,7 @@ function line(interpolate, transform, squaredTolerance) {
   /** @type {Array.<number>} */
   const fractionStack = [1, 0];
 
-  /** @type {Object.<string, boolean>} */
+  /** @type {!Object.<string, boolean>} */
   const fractions = {};
 
   let maxIterations = 1e5;
diff --git a/src/ol/interaction/Modify.js b/src/ol/interaction/Modify.js
index 08c318f8cb..670010660a 100644
--- a/src/ol/interaction/Modify.js
+++ b/src/ol/interaction/Modify.js
@@ -223,7 +223,7 @@ const Modify = function(options) {
   /**
   * @const
   * @private
-  * @type {Object.<string, function(ol.Feature, ol.geom.Geometry)>}
+  * @type {!Object.<string, function(ol.Feature, ol.geom.Geometry)>}
   */
   this.SEGMENT_WRITERS_ = {
     'Point': this.writePointGeometry_,
diff --git a/src/ol/interaction/Pointer.js b/src/ol/interaction/Pointer.js
index 00981d061f..0f5b40a74f 100644
--- a/src/ol/interaction/Pointer.js
+++ b/src/ol/interaction/Pointer.js
@@ -97,7 +97,7 @@ const PointerInteraction = function(opt_options) {
   this.handlingDownUpSequence = false;
 
   /**
-   * @type {Object.<string, ol.pointer.PointerEvent>}
+   * @type {!Object.<string, ol.pointer.PointerEvent>}
    * @private
    */
   this.trackedPointers_ = {};
diff --git a/src/ol/interaction/Snap.js b/src/ol/interaction/Snap.js
index 51f7b95a0c..f3090bfbd7 100644
--- a/src/ol/interaction/Snap.js
+++ b/src/ol/interaction/Snap.js
@@ -97,7 +97,7 @@ const Snap = function(opt_options) {
    * If a feature geometry changes while a pointer drag|move event occurs, the
    * feature doesn't get updated right away.  It will be at the next 'pointerup'
    * event fired.
-   * @type {Object.<number, ol.Feature>}
+   * @type {!Object.<number, ol.Feature>}
    * @private
    */
   this.pendingFeatures_ = {};
diff --git a/src/ol/proj/transforms.js b/src/ol/proj/transforms.js
index 6d3536fd11..4417f30de4 100644
--- a/src/ol/proj/transforms.js
+++ b/src/ol/proj/transforms.js
@@ -6,7 +6,7 @@ import {isEmpty} from '../obj.js';
 
 /**
  * @private
- * @type {Object.<string, Object.<string, ol.TransformFunction>>}
+ * @type {!Object.<string, !Object.<string, ol.TransformFunction>>}
  */
 let transforms = {};
 
diff --git a/src/ol/render/canvas/Replay.js b/src/ol/render/canvas/Replay.js
index cf39fa6794..91ec941fd9 100644
--- a/src/ol/render/canvas/Replay.js
+++ b/src/ol/render/canvas/Replay.js
@@ -129,7 +129,7 @@ const CanvasReplay = function(tolerance, maxExtent, resolution, pixelRatio, over
 
   /**
    * @private
-   * @type {Object.<number,ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>>}
+   * @type {!Object.<number,ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>>}
    */
   this.coordinateCache_ = {};
 
diff --git a/src/ol/render/canvas/ReplayGroup.js b/src/ol/render/canvas/ReplayGroup.js
index d8d7df604b..38bcc251e1 100644
--- a/src/ol/render/canvas/ReplayGroup.js
+++ b/src/ol/render/canvas/ReplayGroup.js
@@ -100,8 +100,7 @@ const CanvasReplayGroup = function(
 
   /**
    * @private
-   * @type {!Object.<string,
-   *        Object.<ol.render.ReplayType, ol.render.canvas.Replay>>}
+   * @type {!Object.<string, !Object.<ol.render.ReplayType, ol.render.canvas.Replay>>}
    */
   this.replaysByZIndex_ = {};
 
diff --git a/src/ol/render/canvas/TextReplay.js b/src/ol/render/canvas/TextReplay.js
index e3131e23cf..1d9922176d 100644
--- a/src/ol/render/canvas/TextReplay.js
+++ b/src/ol/render/canvas/TextReplay.js
@@ -79,7 +79,7 @@ const CanvasTextReplay = function(
   this.textFillState_ = null;
 
   /**
-   * @type {Object.<string, ol.CanvasFillState>}
+   * @type {!Object.<string, ol.CanvasFillState>}
    */
   this.fillStates = {};
 
@@ -90,7 +90,7 @@ const CanvasTextReplay = function(
   this.textStrokeState_ = null;
 
   /**
-   * @type {Object.<string, ol.CanvasStrokeState>}
+   * @type {!Object.<string, ol.CanvasStrokeState>}
    */
   this.strokeStates = {};
 
@@ -101,7 +101,7 @@ const CanvasTextReplay = function(
   this.textState_ = /** @type {ol.CanvasTextState} */ ({});
 
   /**
-   * @type {Object.<string, ol.CanvasTextState>}
+   * @type {!Object.<string, ol.CanvasTextState>}
    */
   this.textStates = {};
 
diff --git a/src/ol/render/webgl/TextureReplay.js b/src/ol/render/webgl/TextureReplay.js
index 2a3894b29f..ceab45f4ff 100644
--- a/src/ol/render/webgl/TextureReplay.js
+++ b/src/ol/render/webgl/TextureReplay.js
@@ -242,9 +242,8 @@ WebGLTextureReplay.prototype.drawCoordinates = function(flatCoordinates, offset,
 /**
  * @protected
  * @param {Array.<WebGLTexture>} textures Textures.
- * @param {Array.<HTMLCanvasElement|HTMLImageElement|HTMLVideoElement>} images
- *    Images.
- * @param {Object.<string, WebGLTexture>} texturePerImage Texture cache.
+ * @param {Array.<HTMLCanvasElement|HTMLImageElement|HTMLVideoElement>} images Images.
+ * @param {!Object.<string, WebGLTexture>} texturePerImage Texture cache.
  * @param {WebGLRenderingContext} gl Gl.
  */
 WebGLTextureReplay.prototype.createTextures = function(textures, images, texturePerImage, gl) {
diff --git a/src/ol/renderer/Layer.js b/src/ol/renderer/Layer.js
index 492c5ef242..8b2cb853c6 100644
--- a/src/ol/renderer/Layer.js
+++ b/src/ol/renderer/Layer.js
@@ -164,7 +164,7 @@ LayerRenderer.prototype.scheduleExpireCache = function(frameState, tileSource) {
 
 
 /**
- * @param {Object.<string, Object.<string, ol.TileRange>>} usedTiles Used tiles.
+ * @param {!Object.<string, !Object.<string, ol.TileRange>>} usedTiles Used tiles.
  * @param {ol.source.Tile} tileSource Tile source.
  * @param {number} z Z.
  * @param {ol.TileRange} tileRange Tile range.
diff --git a/src/ol/renderer/Map.js b/src/ol/renderer/Map.js
index 6aac6da47c..194a20f2e8 100644
--- a/src/ol/renderer/Map.js
+++ b/src/ol/renderer/Map.js
@@ -32,7 +32,7 @@ const MapRenderer = function(container, map) {
 
   /**
    * @private
-   * @type {Object.<string, ol.renderer.Layer>}
+   * @type {!Object.<string, ol.renderer.Layer>}
    */
   this.layerRenderers_ = {};
 
diff --git a/src/ol/renderer/canvas/VectorLayer.js b/src/ol/renderer/canvas/VectorLayer.js
index 19953f6af3..9b8093865e 100644
--- a/src/ol/renderer/canvas/VectorLayer.js
+++ b/src/ol/renderer/canvas/VectorLayer.js
@@ -253,14 +253,13 @@ CanvasVectorLayerRenderer.prototype.forEachFeatureAtCoordinate = function(coordi
     const resolution = frameState.viewState.resolution;
     const rotation = frameState.viewState.rotation;
     const layer = /** @type {ol.layer.Vector} */ (this.getLayer());
-    /** @type {Object.<string, boolean>} */
+    /** @type {!Object.<string, boolean>} */
     const features = {};
-    const result = this.replayGroup_.forEachFeatureAtCoordinate(coordinate, resolution,
-      rotation, hitTolerance, {},
+    const result = this.replayGroup_.forEachFeatureAtCoordinate(coordinate, resolution, rotation, hitTolerance, {},
       /**
-         * @param {ol.Feature|ol.render.Feature} feature Feature.
-         * @return {?} Callback result.
-         */
+       * @param {ol.Feature|ol.render.Feature} feature Feature.
+       * @return {?} Callback result.
+       */
       function(feature) {
         const key = getUid(feature).toString();
         if (!(key in features)) {
diff --git a/src/ol/renderer/canvas/VectorTileLayer.js b/src/ol/renderer/canvas/VectorTileLayer.js
index 51cc0f6f5b..46f005b31a 100644
--- a/src/ol/renderer/canvas/VectorTileLayer.js
+++ b/src/ol/renderer/canvas/VectorTileLayer.js
@@ -265,7 +265,7 @@ CanvasVectorTileLayerRenderer.prototype.forEachFeatureAtCoordinate = function(co
   const rotation = frameState.viewState.rotation;
   hitTolerance = hitTolerance == undefined ? 0 : hitTolerance;
   const layer = this.getLayer();
-  /** @type {Object.<string, boolean>} */
+  /** @type {!Object.<string, boolean>} */
   const features = {};
 
   /** @type {Array.<ol.VectorImageTile>} */
@@ -290,8 +290,7 @@ CanvasVectorTileLayerRenderer.prototype.forEachFeatureAtCoordinate = function(co
         continue;
       }
       replayGroup = sourceTile.getReplayGroup(layer, tile.tileCoord.toString());
-      found = found || replayGroup.forEachFeatureAtCoordinate(
-        coordinate, resolution, rotation, hitTolerance, {},
+      found = found || replayGroup.forEachFeatureAtCoordinate(coordinate, resolution, rotation, hitTolerance, {},
         /**
          * @param {ol.Feature|ol.render.Feature} feature Feature.
          * @return {?} Callback result.
diff --git a/src/ol/renderer/webgl/VectorLayer.js b/src/ol/renderer/webgl/VectorLayer.js
index fc32b07afd..328c32abb2 100644
--- a/src/ol/renderer/webgl/VectorLayer.js
+++ b/src/ol/renderer/webgl/VectorLayer.js
@@ -143,7 +143,7 @@ WebGLVectorLayerRenderer.prototype.forEachFeatureAtCoordinate = function(coordin
     const viewState = frameState.viewState;
     const layer = this.getLayer();
     const layerState = this.layerState_;
-    /** @type {Object.<string, boolean>} */
+    /** @type {!Object.<string, boolean>} */
     const features = {};
     return this.replayGroup_.forEachFeatureAtCoordinate(coordinate,
       context, viewState.center, viewState.resolution, viewState.rotation,
diff --git a/src/ol/source/TileImage.js b/src/ol/source/TileImage.js
index d630746da0..2da8c2ee29 100644
--- a/src/ol/source/TileImage.js
+++ b/src/ol/source/TileImage.js
@@ -61,13 +61,13 @@ const TileImage = function(options) {
 
   /**
    * @protected
-   * @type {Object.<string, ol.TileCache>}
+   * @type {!Object.<string, ol.TileCache>}
    */
   this.tileCacheForProjection = {};
 
   /**
    * @protected
-   * @type {Object.<string, ol.tilegrid.TileGrid>}
+   * @type {!Object.<string, ol.tilegrid.TileGrid>}
    */
   this.tileGridForProjection = {};
 
@@ -173,8 +173,7 @@ TileImage.prototype.getTileGridForProjection = function(projection) {
   } else {
     const projKey = getUid(projection).toString();
     if (!(projKey in this.tileGridForProjection)) {
-      this.tileGridForProjection[projKey] =
-          getTileGridForProjection(projection);
+      this.tileGridForProjection[projKey] = getTileGridForProjection(projection);
     }
     return /** @type {!ol.tilegrid.TileGrid} */ (this.tileGridForProjection[projKey]);
   }
diff --git a/src/ol/source/UrlTile.js b/src/ol/source/UrlTile.js
index e3cfd1312e..11e7c3b514 100644
--- a/src/ol/source/UrlTile.js
+++ b/src/ol/source/UrlTile.js
@@ -63,7 +63,7 @@ const UrlTile = function(options) {
 
   /**
    * @private
-   * @type {Object.<number, boolean>}
+   * @type {!Object.<number, boolean>}
    */
   this.tileLoadingKeys_ = {};
 
diff --git a/src/ol/source/Vector.js b/src/ol/source/Vector.js
index 01aa6702da..9208832806 100644
--- a/src/ol/source/Vector.js
+++ b/src/ol/source/Vector.js
@@ -126,21 +126,21 @@ const VectorSource = function(opt_options) {
 
   /**
    * @private
-   * @type {Object.<string, ol.Feature>}
+   * @type {!Object.<string, ol.Feature>}
    */
   this.nullGeometryFeatures_ = {};
 
   /**
    * A lookup of features by id (the return from feature.getId()).
    * @private
-   * @type {Object.<string, ol.Feature>}
+   * @type {!Object.<string, ol.Feature>}
    */
   this.idIndex_ = {};
 
   /**
    * A lookup of features without id (keyed by ol.getUid(feature)).
    * @private
-   * @type {Object.<string, ol.Feature>}
+   * @type {!Object.<string, ol.Feature>}
    */
   this.undefIdIndex_ = {};
 
diff --git a/src/ol/source/WMTS.js b/src/ol/source/WMTS.js
index 8f2d2e7ffb..dd631611e8 100644
--- a/src/ol/source/WMTS.js
+++ b/src/ol/source/WMTS.js
@@ -288,7 +288,7 @@ WMTS.prototype.updateDimensions = function(dimensions) {
 /**
  * Generate source options from a capabilities object.
  * @param {Object} wmtsCap An object representing the capabilities document.
- * @param {Object} config Configuration properties for the layer.  Defaults for
+ * @param {!Object} config Configuration properties for the layer.  Defaults for
  *                  the layer will apply if not provided.
  *
  * Required config properties:
diff --git a/src/ol/structs/PriorityQueue.js b/src/ol/structs/PriorityQueue.js
index ff800bced3..ef2513a99d 100644
--- a/src/ol/structs/PriorityQueue.js
+++ b/src/ol/structs/PriorityQueue.js
@@ -46,7 +46,7 @@ const PriorityQueue = function(priorityFunction, keyFunction) {
   this.priorities_ = [];
 
   /**
-   * @type {Object.<string, boolean>}
+   * @type {!Object.<string, boolean>}
    * @private
    */
   this.queuedElements_ = {};
diff --git a/src/ol/style/IconImageCache.js b/src/ol/style/IconImageCache.js
index 5323fb21e0..c0d65d4b7e 100644
--- a/src/ol/style/IconImageCache.js
+++ b/src/ol/style/IconImageCache.js
@@ -10,7 +10,7 @@ import {asString} from '../color.js';
 const IconImageCache = function() {
 
   /**
-   * @type {Object.<string, ol.style.IconImage>}
+   * @type {!Object.<string, ol.style.IconImage>}
    * @private
    */
   this.cache_ = {};
diff --git a/src/ol/webgl/Context.js b/src/ol/webgl/Context.js
index 658eca2d29..b9cca14be0 100644
--- a/src/ol/webgl/Context.js
+++ b/src/ol/webgl/Context.js
@@ -34,19 +34,19 @@ const WebGLContext = function(canvas, gl) {
 
   /**
    * @private
-   * @type {Object.<string, ol.WebglBufferCacheEntry>}
+   * @type {!Object.<string, ol.WebglBufferCacheEntry>}
    */
   this.bufferCache_ = {};
 
   /**
    * @private
-   * @type {Object.<string, WebGLShader>}
+   * @type {!Object.<string, WebGLShader>}
    */
   this.shaderCache_ = {};
 
   /**
    * @private
-   * @type {Object.<string, WebGLProgram>}
+   * @type {!Object.<string, WebGLProgram>}
    */
   this.programCache_ = {};
 
diff --git a/src/ol/xml.js b/src/ol/xml.js
index b9cb5b2022..c7194f0e1d 100644
--- a/src/ol/xml.js
+++ b/src/ol/xml.js
@@ -133,8 +133,7 @@ export function makeArrayExtender(valueReader, opt_this) {
     function(node, objectStack) {
       const value = valueReader.call(opt_this, node, objectStack);
       if (value !== undefined) {
-        const array = /** @type {Array.<*>} */
-              (objectStack[objectStack.length - 1]);
+        const array = /** @type {Array.<*>} */ (objectStack[objectStack.length - 1]);
         extend(array, value);
       }
     }
@@ -157,8 +156,7 @@ export function makeArrayPusher(valueReader, opt_this) {
      * @param {Array.<*>} objectStack Object stack.
      */
     function(node, objectStack) {
-      const value = valueReader.call(opt_this !== undefined ? opt_this : this,
-        node, objectStack);
+      const value = valueReader.call(opt_this !== undefined ? opt_this : this, node, objectStack);
       if (value !== undefined) {
         const array = objectStack[objectStack.length - 1];
         array.push(value);
@@ -182,8 +180,7 @@ export function makeReplacer(valueReader, opt_this) {
      * @param {Array.<*>} objectStack Object stack.
      */
     function(node, objectStack) {
-      const value = valueReader.call(opt_this !== undefined ? opt_this : this,
-        node, objectStack);
+      const value = valueReader.call(opt_this !== undefined ? opt_this : this, node, objectStack);
       if (value !== undefined) {
         objectStack[objectStack.length - 1] = value;
       }
@@ -207,13 +204,10 @@ export function makeObjectPropertyPusher(valueReader, opt_property, opt_this) {
      * @param {Array.<*>} objectStack Object stack.
      */
     function(node, objectStack) {
-      const value = valueReader.call(opt_this !== undefined ? opt_this : this,
-        node, objectStack);
+      const value = valueReader.call(opt_this !== undefined ? opt_this : this, node, objectStack);
       if (value !== undefined) {
-        const object = /** @type {Object} */
-              (objectStack[objectStack.length - 1]);
-        const property = opt_property !== undefined ?
-          opt_property : node.localName;
+        const object = /** @type {!Object} */ (objectStack[objectStack.length - 1]);
+        const property = opt_property !== undefined ? opt_property : node.localName;
         let array;
         if (property in object) {
           array = object[property];
@@ -241,13 +235,10 @@ export function makeObjectPropertySetter(valueReader, opt_property, opt_this) {
      * @param {Array.<*>} objectStack Object stack.
      */
     function(node, objectStack) {
-      const value = valueReader.call(opt_this !== undefined ? opt_this : this,
-        node, objectStack);
+      const value = valueReader.call(opt_this !== undefined ? opt_this : this, node, objectStack);
       if (value !== undefined) {
-        const object = /** @type {Object} */
-              (objectStack[objectStack.length - 1]);
-        const property = opt_property !== undefined ?
-          opt_property : node.localName;
+        const object = /** @type {!Object} */ (objectStack[objectStack.length - 1]);
+        const property = opt_property !== undefined ? opt_property : node.localName;
         object[property] = value;
       }
     });
@@ -266,8 +257,7 @@ export function makeObjectPropertySetter(valueReader, opt_property, opt_this) {
  */
 export function makeChildAppender(nodeWriter, opt_this) {
   return function(node, value, objectStack) {
-    nodeWriter.call(opt_this !== undefined ? opt_this : this,
-      node, value, objectStack);
+    nodeWriter.call(opt_this !== undefined ? opt_this : this, node, value, objectStack);
     const parent = objectStack[objectStack.length - 1];
     const parentNode = parent.node;
     parentNode.appendChild(node);
@@ -430,11 +420,10 @@ export function parseNode(parsersNS, node, objectStack, opt_this) {
  * @return {T} Object.
  * @template T
  */
-export function pushParseAndPop(
-  object, parsersNS, node, objectStack, opt_this) {
+export function pushParseAndPop(object, parsersNS, node, objectStack, opt_this) {
   objectStack.push(object);
   parseNode(parsersNS, node, objectStack, opt_this);
-  return objectStack.pop();
+  return /** @type {T} */ (objectStack.pop());
 }
 
 
@@ -501,10 +490,8 @@ export function serialize(
  * @return {O|undefined} Object.
  * @template O, T
  */
-export function pushSerializeAndPop(object,
-  serializersNS, nodeFactory, values, objectStack, opt_keys, opt_this) {
+export function pushSerializeAndPop(object, serializersNS, nodeFactory, values, objectStack, opt_keys, opt_this) {
   objectStack.push(object);
-  serialize(
-    serializersNS, nodeFactory, values, objectStack, opt_keys, opt_this);
-  return objectStack.pop();
+  serialize(serializersNS, nodeFactory, values, objectStack, opt_keys, opt_this);
+  return /** @type {O|undefined} */ (objectStack.pop());
 }