diff --git a/core/block.ts b/core/block.ts
index 1ac77cd5492..9e345e1d8e1 100644
--- a/core/block.ts
+++ b/core/block.ts
@@ -221,9 +221,7 @@ export class Block implements IASTNodeLocation, IDeletable {
   type!: string;
   // Record initial inline state.
   inputsInlineDefault?: boolean;
-  // Setting this to null indicates that the block has been disposed. Must be
-  // nullable.
-  workspace: Workspace|null;
+  workspace: Workspace;
 
   /**
    * @param workspace The block's workspace.
@@ -317,7 +315,7 @@ export class Block implements IASTNodeLocation, IDeletable {
    * @suppress {checkTypes}
    */
   dispose(healStack: boolean) {
-    if (!this.workspace) {
+    if (this.disposed) {
       // Already deleted.
       return;
     }
@@ -335,13 +333,10 @@ export class Block implements IASTNodeLocation, IDeletable {
     try {
       // This block is now at the top of the workspace.
       // Remove this block from the workspace's list of top-most blocks.
-      if (this.workspace) {
-        this.workspace.removeTopBlock(this);
-        this.workspace.removeTypedBlock(this);
-        // Remove from block database.
-        this.workspace.removeBlockById(this.id);
-        this.workspace = null;
-      }
+      this.workspace.removeTopBlock(this);
+      this.workspace.removeTypedBlock(this);
+      // Remove from block database.
+      this.workspace.removeBlockById(this.id);
 
       // First, dispose of all my children.
       for (let i = this.childBlocks_.length - 1; i >= 0; i--) {
@@ -428,7 +423,7 @@ export class Block implements IASTNodeLocation, IDeletable {
     // Disconnect the child block.
     childConnection?.disconnect();
     // Connect child to the parent if possible, otherwise bump away.
-    if (this.workspace!.connectionChecker.canConnect(
+    if (this.workspace.connectionChecker.canConnect(
             childConnection, parentConnection, false)) {
       parentConnection.connect(childConnection!);
     } else {
@@ -481,7 +476,7 @@ export class Block implements IASTNodeLocation, IDeletable {
       const nextTarget = this.nextConnection.targetConnection;
       nextTarget?.disconnect();
       if (previousTarget &&
-          this.workspace!.connectionChecker.canConnect(
+          this.workspace.connectionChecker.canConnect(
               previousTarget, nextTarget, false)) {
         // Attach the next statement to the previous statement.
         previousTarget.connect(nextTarget!);
@@ -721,7 +716,7 @@ export class Block implements IASTNodeLocation, IDeletable {
     } else {
       // New parent must be non-null so remove this block from the workspace's
       //     list of top-most blocks.
-      this.workspace!.removeTopBlock(this);
+      this.workspace.removeTopBlock(this);
     }
 
     this.parentBlock_ = newParent;
@@ -729,7 +724,7 @@ export class Block implements IASTNodeLocation, IDeletable {
       // Add this block to the new parent's child list.
       newParent.childBlocks_.push(this);
     } else {
-      this.workspace!.addTopBlock(this);
+      this.workspace.addTopBlock(this);
     }
   }
 
@@ -759,8 +754,8 @@ export class Block implements IASTNodeLocation, IDeletable {
    * @return True if deletable.
    */
   isDeletable(): boolean {
-    return this.deletable_ && !this.isShadow_ &&
-        !(this.workspace && this.workspace.options.readOnly);
+    return this.deletable_ && !this.isShadow_ && !this.disposed &&
+        !this.workspace.options.readOnly;
   }
 
   /**
@@ -776,8 +771,8 @@ export class Block implements IASTNodeLocation, IDeletable {
    * @return True if movable.
    */
   isMovable(): boolean {
-    return this.movable_ && !this.isShadow_ &&
-        !(this.workspace && this.workspace.options.readOnly);
+    return this.movable_ && !this.isShadow_ && !this.disposed &&
+        !this.workspace.options.readOnly;
   }
 
   /**
@@ -796,10 +791,10 @@ export class Block implements IASTNodeLocation, IDeletable {
    * @return True if duplicatable.
    */
   isDuplicatable(): boolean {
-    if (!this.workspace!.hasBlockLimits()) {
+    if (!this.workspace.hasBlockLimits()) {
       return true;
     }
-    return this.workspace!.isCapacityAvailable(
+    return this.workspace.isCapacityAvailable(
         common.getBlockTypeCounts(this, true));
   }
 
@@ -843,8 +838,7 @@ export class Block implements IASTNodeLocation, IDeletable {
    * @return True if editable.
    */
   isEditable(): boolean {
-    return this.editable_ &&
-        !(this.workspace && this.workspace.options.readOnly);
+    return this.editable_ && !this.disposed && !this.workspace.options.readOnly;
   }
 
   /**
@@ -974,11 +968,11 @@ export class Block implements IASTNodeLocation, IDeletable {
       throw Error('onchange must be a function.');
     }
     if (this.onchangeWrapper_) {
-      this.workspace!.removeChangeListener(this.onchangeWrapper_);
+      this.workspace.removeChangeListener(this.onchangeWrapper_);
     }
     this.onchange = onchangeFn;
     this.onchangeWrapper_ = onchangeFn.bind(this);
-    this.workspace!.addChangeListener(this.onchangeWrapper_);
+    this.workspace.addChangeListener(this.onchangeWrapper_);
   }
 
   /**
@@ -1031,7 +1025,7 @@ export class Block implements IASTNodeLocation, IDeletable {
       for (let j = 0, field; field = input.fieldRow[j]; j++) {
         if (field.referencesVariables()) {
           const model =
-              this.workspace!.getVariableById(field.getValue() as string);
+              this.workspace.getVariableById(field.getValue() as string);
           // Check if the variable actually exists (and isn't just a potential
           // variable).
           if (model) {
diff --git a/core/block_animations.ts b/core/block_animations.ts
index a999ee745bf..104ef0b38ee 100644
--- a/core/block_animations.ts
+++ b/core/block_animations.ts
@@ -42,7 +42,7 @@ let disconnectGroup: Element = null as AnyDuringMigration;
  * @internal
  */
 export function disposeUiEffect(block: BlockSvg) {
-  const workspace = block.workspace!;
+  const workspace = block.workspace;
   const svgGroup = block.getSvgRoot();
   workspace.getAudioManager().play('delete');
 
@@ -100,7 +100,7 @@ function disposeUiStep(
  * @internal
  */
 export function connectionUiEffect(block: BlockSvg) {
-  const workspace = block.workspace!;
+  const workspace = block.workspace;
   const scale = workspace.scale;
   workspace.getAudioManager().play('click');
   if (scale < 1) {
@@ -157,8 +157,8 @@ function connectionUiStep(ripple: SVGElement, start: Date, scale: number) {
  * @internal
  */
 export function disconnectUiEffect(block: BlockSvg) {
-  block.workspace!.getAudioManager().play('disconnect');
-  if (block.workspace!.scale < 1) {
+  block.workspace.getAudioManager().play('disconnect');
+  if (block.workspace.scale < 1) {
     return;  // Too small to care about visual effects.
   }
   // Horizontal distance for bottom of block to wiggle.
diff --git a/core/block_dragger.ts b/core/block_dragger.ts
index 9ce8b6b9eb8..c540fd2a8a3 100644
--- a/core/block_dragger.ts
+++ b/core/block_dragger.ts
@@ -242,7 +242,7 @@ export class BlockDragger implements IBlockDragger {
         // Blocks dragged directly from a flyout may need to be bumped into
         // bounds.
         bumpObjects.bumpIntoBounds(
-            this.draggingBlock_.workspace!,
+            this.draggingBlock_.workspace,
             this.workspace_.getMetricsManager().getScrollMetrics(true),
             this.draggingBlock_);
       }
diff --git a/core/block_svg.ts b/core/block_svg.ts
index aac747b717e..e937c42a3d9 100644
--- a/core/block_svg.ts
+++ b/core/block_svg.ts
@@ -144,7 +144,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
   /** Whether mousedown events have been bound yet. */
   private eventsInit_ = false;
 
-  override workspace: WorkspaceSvg|null;
+  override workspace: WorkspaceSvg;
   // TODO(b/109816955): remove '!', see go/strict-prop-init-fix.
   override outputConnection!: RenderedConnection;
   // TODO(b/109816955): remove '!', see go/strict-prop-init-fix.
@@ -223,7 +223,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * May be called more than once.
    */
   initSvg() {
-    if (!this.workspace!.rendered) {
+    if (!this.workspace.rendered) {
       throw TypeError('Workspace is headless.');
     }
     for (let i = 0, input; input = this.inputList[i]; i++) {
@@ -236,13 +236,13 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     this.applyColour();
     this.pathObject.updateMovable(this.isMovable());
     const svg = this.getSvgRoot();
-    if (!this.workspace!.options.readOnly && !this.eventsInit_ && svg) {
+    if (!this.workspace.options.readOnly && !this.eventsInit_ && svg) {
       browserEvents.conditionalBind(svg, 'mousedown', this, this.onMouseDown_);
     }
     this.eventsInit_ = true;
 
     if (!svg.parentNode) {
-      this.workspace!.getCanvas().appendChild(svg);
+      this.workspace.getCanvas().appendChild(svg);
     }
   }
 
@@ -287,7 +287,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       }
     }
     const event = new (eventUtils.get(eventUtils.SELECTED))!
-        (oldId, this.id, this.workspace!.id);
+        (oldId, this.id, this.workspace.id);
     eventUtils.fire(event);
     common.setSelected(this);
     this.addSelect();
@@ -302,8 +302,8 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       return;
     }
     const event = new (eventUtils.get(eventUtils.SELECTED))!
-        (this.id, null, this.workspace!.id);
-    event.workspaceId = this.workspace!.id;
+        (this.id, null, this.workspace.id);
+    event.workspaceId = this.workspace.id;
     eventUtils.fire(event);
     common.setSelected(null);
     this.removeSelect();
@@ -348,7 +348,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
 
     // Bail early if workspace is clearing, or we aren't rendered.
     // We won't need to reattach ourselves anywhere.
-    if (this.workspace!.isClearing || !svgRoot) {
+    if (this.workspace.isClearing || !svgRoot) {
       return;
     }
 
@@ -361,7 +361,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     } else if (oldParent) {
       // If we are losing a parent, we want to move our DOM element to the
       // root of the workspace.
-      this.workspace!.getCanvas().appendChild(svgRoot);
+      this.workspace.getCanvas().appendChild(svgRoot);
       this.translate(oldXY.x, oldXY.y);
     }
 
@@ -381,7 +381,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     let y = 0;
 
     const dragSurfaceGroup = this.useDragSurface_ ?
-        this.workspace!.getBlockDragSurface()!.getGroup() :
+        this.workspace.getBlockDragSurface()!.getGroup() :
         null;
 
     let element: SVGElement = this.getSvgRoot();
@@ -394,15 +394,15 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
         // If this element is the current element on the drag surface, include
         // the translation of the drag surface itself.
         if (this.useDragSurface_ &&
-            this.workspace!.getBlockDragSurface()!.getCurrentBlock() ===
+            this.workspace.getBlockDragSurface()!.getCurrentBlock() ===
                 element) {
           const surfaceTranslation =
-              this.workspace!.getBlockDragSurface()!.getSurfaceTranslation();
+              this.workspace.getBlockDragSurface()!.getSurfaceTranslation();
           x += surfaceTranslation.x;
           y += surfaceTranslation.y;
         }
         element = element.parentNode as SVGElement;
-      } while (element && element !== this.workspace!.getCanvas() &&
+      } while (element && element !== this.workspace.getCanvas() &&
                element !== dragSurfaceGroup);
     }
     return new Coordinate(x, y);
@@ -429,7 +429,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       event!.recordNew();
       eventUtils.fire(event);
     }
-    this.workspace!.resizeContents();
+    this.workspace.resizeContents();
   }
 
   /**
@@ -459,11 +459,11 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     // This is in workspace coordinates.
     const xy = this.getRelativeToSurfaceXY();
     this.clearTransformAttributes_();
-    this.workspace!.getBlockDragSurface()!.translateSurface(xy.x, xy.y);
+    this.workspace.getBlockDragSurface()!.translateSurface(xy.x, xy.y);
     // Execute the move on the top-level SVG component
     const svg = this.getSvgRoot();
     if (svg) {
-      this.workspace!.getBlockDragSurface()!.setBlocksAndShow(svg);
+      this.workspace.getBlockDragSurface()!.setBlocksAndShow(svg);
     }
   }
 
@@ -490,8 +490,8 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     }
     // Translate to current position, turning off 3d.
     this.translate(newXY.x, newXY.y);
-    this.workspace!.getBlockDragSurface()!.clearAndHide(
-        this.workspace!.getCanvas());
+    this.workspace.getBlockDragSurface()!.clearAndHide(
+        this.workspace.getCanvas());
   }
 
   /**
@@ -503,7 +503,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    */
   moveDuringDrag(newLoc: Coordinate) {
     if (this.useDragSurface_) {
-      this.workspace!.getBlockDragSurface()!.translateSurface(
+      this.workspace.getBlockDragSurface()!.translateSurface(
           newLoc.x, newLoc.y);
     } else {
       (this.svgGroup_ as AnyDuringMigration).translate_ =
@@ -526,10 +526,10 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
 
   /** Snap this block to the nearest grid point. */
   snapToGrid() {
-    if (!this.workspace) {
+    if (this.disposed) {
       return;  // Deleted block.
     }
-    if (this.workspace!.isDragging()) {
+    if (this.workspace.isDragging()) {
       return  // Don't bump blocks during a drag.;
     }
 
@@ -539,7 +539,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     if (this.isInFlyout) {
       return;  // Don't move blocks around in a flyout.
     }
-    const grid = this.workspace!.getGrid();
+    const grid = this.workspace.getGrid();
     if (!grid || !grid.shouldSnap()) {
       return;  // Config says no snapping.
     }
@@ -581,7 +581,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * A dirty field is a field that needs to be re-rendered.
    */
   markDirty() {
-    this.pathObject.constants = this.workspace!.getRenderer().getConstants();
+    this.pathObject.constants = this.workspace.getRenderer().getConstants();
     for (let i = 0, input; input = this.inputList[i]; i++) {
       input.markDirty();
     }
@@ -667,8 +667,8 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       nextField.showEditor();
 
       // Also move the cursor if we're in keyboard nav mode.
-      if (this.workspace!.keyboardAccessibilityMode) {
-        this.workspace!.getCursor()!.setCurNode(nextNode);
+      if (this.workspace.keyboardAccessibilityMode) {
+        this.workspace.getCursor()!.setCurNode(nextNode);
       }
     }
   }
@@ -678,7 +678,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * @param e Mouse down event or touch start event.
    */
   private onMouseDown_(e: Event) {
-    const gesture = this.workspace && this.workspace!.getGesture(e);
+    const gesture = this.workspace.getGesture(e);
     if (gesture) {
       gesture.handleBlockStart(e, this);
     }
@@ -702,7 +702,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    */
   protected generateContextMenu():
       Array<ContextMenuOption|LegacyContextMenuOption>|null {
-    if (this.workspace!.options.readOnly || !this.contextMenu) {
+    if (this.workspace.options.readOnly || !this.contextMenu) {
       return null;
     }
     // AnyDuringMigration because:  Argument of type '{ block: this; }' is not
@@ -830,7 +830,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     this.isInsertionMarker_ = insertionMarker;
     if (this.isInsertionMarker_) {
       this.setColour(
-          this.workspace!.getRenderer().getConstants().INSERTION_MARKER_COLOUR);
+          this.workspace.getRenderer().getConstants().INSERTION_MARKER_COLOUR);
       this.pathObject.updateInsertionMarker(true);
     }
   }
@@ -852,7 +852,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * @suppress {checkTypes}
    */
   override dispose(healStack?: boolean, animate?: boolean) {
-    if (!this.workspace) {
+    if (this.disposed) {
       // The block has already been deleted.
       return;
     }
@@ -865,7 +865,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     // If this block is being dragged, unlink the mouse events.
     if (common.getSelected() === this) {
       this.unselect();
-      this.workspace!.cancelCurrentGesture();
+      this.workspace.cancelCurrentGesture();
     }
     // If this block has a context menu open, close it.
     if (ContextMenu.getCurrentBlock() === this) {
@@ -920,11 +920,11 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * grouping, or hide chaff, then use `block.dispose()` directly.
    */
   checkAndDelete() {
-    if (this.workspace!.isFlyout) {
+    if (this.workspace.isFlyout) {
       return;
     }
     eventUtils.setGroup(true);
-    this.workspace!.hideChaff();
+    this.workspace.hideChaff();
     if (this.outputConnection) {
       // Do not attempt to heal rows
       // (https://github.com/google/blockly/issues/4832)
@@ -953,7 +953,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
                     this as AnyDuringMigration,
                     {addCoordinates: true, addNextBlocks: false}) as
           blocks.State,
-      source: this.workspace!,
+      source: this.workspace,
       typeCounts: common.getBlockTypeCounts(this as AnyDuringMigration, true),
     };
   }
@@ -1062,12 +1062,12 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       clearTimeout(this.warningTextDb_[id]);
       delete this.warningTextDb_[id];
     }
-    if (this.workspace!.isDragging()) {
+    if (this.workspace.isDragging()) {
       // Don't change the warning text during a drag.
       // Wait until the drag finishes.
       const thisBlock = this;
       this.warningTextDb_[id] = setTimeout(function() {
-        if (thisBlock.workspace) {  // Check block wasn't deleted.
+        if (!thisBlock.disposed) {  // Check block wasn't deleted.
           delete thisBlock.warningTextDb_[id];
           thisBlock.setWarningText(text, id);
         }
@@ -1212,7 +1212,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
   override setColour(colour: number|string) {
     super.setColour(colour);
     const styleObj =
-        this.workspace!.getRenderer().getConstants().getBlockStyleForColour(
+        this.workspace.getRenderer().getConstants().getBlockStyleForColour(
             this.colour_);
 
     this.pathObject.setStyle(styleObj.style);
@@ -1229,7 +1229,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    */
   override setStyle(blockStyleName: string) {
     const blockStyle =
-        this.workspace!.getRenderer().getConstants().getBlockStyle(
+        this.workspace.getRenderer().getConstants().getBlockStyle(
             blockStyleName);
     this.styleName_ = blockStyleName;
 
@@ -1516,10 +1516,10 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
    * connected should not coincidentally line up on screen.
    */
   override bumpNeighbours() {
-    if (!this.workspace) {
+    if (this.disposed) {
       return;  // Deleted block.
     }
-    if (this.workspace!.isDragging()) {
+    if (this.workspace.isDragging()) {
       return;  // Don't bump blocks during a drag.
     }
     const rootBlock = this.getRootBlock();
@@ -1639,7 +1639,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
       if (this.isCollapsed()) {
         this.updateCollapsed_();
       }
-      this.workspace!.getRenderer().render(this);
+      this.workspace.getRenderer().render(this);
       this.updateConnectionLocations_();
 
       if (opt_bubble !== false) {
@@ -1648,7 +1648,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
           parentBlock.render(true);
         } else {
           // Top-most block. Fire an event to allow scrollbars to resize.
-          this.workspace!.resizeContents();
+          this.workspace.resizeContents();
         }
       }
 
@@ -1661,14 +1661,12 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
 
   /** Redraw any attached marker or cursor svgs if needed. */
   protected updateMarkers_() {
-    if (this.workspace!.keyboardAccessibilityMode &&
-        this.pathObject.cursorSvg) {
-      this.workspace!.getCursor()!.draw();
+    if (this.workspace.keyboardAccessibilityMode && this.pathObject.cursorSvg) {
+      this.workspace.getCursor()!.draw();
     }
-    if (this.workspace!.keyboardAccessibilityMode &&
-        this.pathObject.markerSvg) {
+    if (this.workspace.keyboardAccessibilityMode && this.pathObject.markerSvg) {
       // TODO(#4592): Update all markers on the block.
-      this.workspace!.getMarker(MarkerManager.LOCAL_MARKER)!.draw();
+      this.workspace.getMarker(MarkerManager.LOCAL_MARKER)!.draw();
     }
   }
 
@@ -1740,7 +1738,7 @@ export class BlockSvg extends Block implements IASTNodeLocationSvg,
     if (nextBlock) {
       const nextHeightWidth = nextBlock.getHeightWidth();
       const tabHeight =
-          this.workspace!.getRenderer().getConstants().NOTCH_HEIGHT;
+          this.workspace.getRenderer().getConstants().NOTCH_HEIGHT;
       height += nextHeightWidth.height - tabHeight;
       width = Math.max(width, nextHeightWidth.width);
     }
diff --git a/core/comment.ts b/core/comment.ts
index 36b6a8d6ddf..e6759d2d054 100644
--- a/core/comment.ts
+++ b/core/comment.ts
@@ -271,7 +271,7 @@ export class Comment extends Icon {
   /** Show an editable bubble. */
   private createEditableBubble_() {
     this.bubble_ = new Bubble(
-        this.block_.workspace!, this.createEditor_(),
+        this.block_.workspace, this.createEditor_(),
         this.block_.pathObject.svgPath, (this.iconXY_ as Coordinate),
         this.model_.size.width, this.model_.size.height);
     // Expose this comment's block's ID on its top-level SVG group.
diff --git a/core/connection.ts b/core/connection.ts
index 8dd84f13510..47792ed5435 100644
--- a/core/connection.ts
+++ b/core/connection.ts
@@ -197,7 +197,7 @@ export class Connection implements IASTNodeLocationWithBlock {
    * @internal
    */
   getConnectionChecker(): IConnectionChecker {
-    return this.sourceBlock_.workspace!.connectionChecker;
+    return this.sourceBlock_.workspace.connectionChecker;
   }
 
   /**
@@ -563,7 +563,7 @@ export class Connection implements IASTNodeLocationWithBlock {
     const parentBlock = this.getSourceBlock();
     const shadowState = this.getShadowState();
     const shadowDom = this.getShadowDom();
-    if (!parentBlock.workspace || !shadowState && !shadowDom) {
+    if (parentBlock.disposed || !shadowState && !shadowDom) {
       return null;
     }
 
diff --git a/core/contextmenu_items.ts b/core/contextmenu_items.ts
index 30441cfb819..df8c246924f 100644
--- a/core/contextmenu_items.ts
+++ b/core/contextmenu_items.ts
@@ -250,7 +250,7 @@ function deleteNext_(deleteList: BlockSvg[], eventGroup: string) {
   eventUtils.setGroup(eventGroup);
   const block = deleteList.shift();
   if (block) {
-    if (block.workspace) {
+    if (!block.disposed) {
       block.dispose(false, true);
       setTimeout(deleteNext_, DELAY, deleteList, eventGroup);
     } else {
@@ -372,7 +372,7 @@ export function registerComment() {
       const block = scope.block;
       // IE doesn't support necessary features for comment editing.
       if (!userAgent.IE && !block!.isInFlyout &&
-          block!.workspace!.options.comments && !block!.isCollapsed() &&
+          block!.workspace.options.comments && !block!.isCollapsed() &&
           block!.isEditable()) {
         return 'enabled';
       }
@@ -440,7 +440,7 @@ export function registerCollapseExpandBlock() {
     preconditionFn(scope: Scope) {
       const block = scope.block;
       if (!block!.isInFlyout && block!.isMovable() &&
-          block!.workspace!.options.collapse) {
+          block!.workspace.options.collapse) {
         return 'enabled';
       }
       return 'hidden';
@@ -467,7 +467,7 @@ export function registerDisable() {
     },
     preconditionFn(scope: Scope) {
       const block = scope.block;
-      if (!block!.isInFlyout && block!.workspace!.options.disable &&
+      if (!block!.isInFlyout && block!.workspace.options.disable &&
           block!.isEditable()) {
         if (block!.getInheritedDisabled()) {
           return 'disabled';
diff --git a/core/dropdowndiv.ts b/core/dropdowndiv.ts
index bda20ee5a2b..b6a6def74a3 100644
--- a/core/dropdowndiv.ts
+++ b/core/dropdowndiv.ts
@@ -226,7 +226,7 @@ export function showPositionedByField(
  */
 function getScaledBboxOfBlock(block: BlockSvg): Rect {
   const blockSvg = block.getSvgRoot();
-  const scale = block.workspace!.scale;
+  const scale = block.workspace.scale;
   const scaledHeight = block.height * scale;
   const scaledWidth = block.width * scale;
   const xy = style.getPageOffset(blockSvg);
@@ -268,7 +268,7 @@ function showPositionedByRect(
   }
   const sourceBlock = field.getSourceBlock() as BlockSvg;
   // Set bounds to main workspace; show the drop-down.
-  let workspace = sourceBlock.workspace!;
+  let workspace = sourceBlock.workspace;
   while (workspace.options.parentWorkspace) {
     workspace = workspace.options.parentWorkspace;
   }
diff --git a/core/events/events_block_base.ts b/core/events/events_block_base.ts
index 86f6e04c2db..b9359f4e01d 100644
--- a/core/events/events_block_base.ts
+++ b/core/events/events_block_base.ts
@@ -41,7 +41,7 @@ export class BlockBase extends AbstractEvent {
     this.blockId = this.isBlank ? '' : opt_block!.id;
 
     /** The workspace identifier for this event. */
-    this.workspaceId = this.isBlank ? '' : opt_block!.workspace?.id ?? '';
+    this.workspaceId = this.isBlank ? '' : opt_block!.workspace.id;
   }
 
   /**
diff --git a/core/events/events_block_drag.ts b/core/events/events_block_drag.ts
index 266a3d102f0..84860e73795 100644
--- a/core/events/events_block_drag.ts
+++ b/core/events/events_block_drag.ts
@@ -41,7 +41,7 @@ export class BlockDrag extends UiBase {
    *     event.
    */
   constructor(opt_block?: Block, opt_isStart?: boolean, opt_blocks?: Block[]) {
-    const workspaceId = opt_block ? opt_block.workspace?.id : undefined;
+    const workspaceId = opt_block ? opt_block.workspace.id : undefined;
     super(workspaceId);
     this.blockId = opt_block ? opt_block.id : null;
 
diff --git a/core/events/events_bubble_open.ts b/core/events/events_bubble_open.ts
index f599d139995..aad69b1331b 100644
--- a/core/events/events_bubble_open.ts
+++ b/core/events/events_bubble_open.ts
@@ -41,7 +41,7 @@ export class BubbleOpen extends UiBase {
    */
   constructor(
       opt_block: BlockSvg, opt_isOpen?: boolean, opt_bubbleType?: string) {
-    const workspaceId = opt_block ? opt_block.workspace!.id : undefined;
+    const workspaceId = opt_block ? opt_block.workspace.id : undefined;
     super(workspaceId);
     this.blockId = opt_block ? opt_block.id : null;
 
diff --git a/core/events/events_click.ts b/core/events/events_click.ts
index 513f1f86461..a58a7b8acb4 100644
--- a/core/events/events_click.ts
+++ b/core/events/events_click.ts
@@ -43,7 +43,7 @@ export class Click extends UiBase {
   constructor(
       opt_block?: Block|null, opt_workspaceId?: string|null,
       opt_targetType?: string) {
-    let workspaceId = opt_block ? opt_block.workspace!.id : opt_workspaceId;
+    let workspaceId = opt_block ? opt_block.workspace.id : opt_workspaceId;
     if (workspaceId === null) {
       workspaceId = undefined;
     }
diff --git a/core/events/events_marker_move.ts b/core/events/events_marker_move.ts
index 12feb7c2f9b..f91246a95e7 100644
--- a/core/events/events_marker_move.ts
+++ b/core/events/events_marker_move.ts
@@ -48,7 +48,7 @@ export class MarkerMove extends UiBase {
   constructor(
       opt_block?: Block|null, isCursor?: boolean, opt_oldNode?: ASTNode|null,
       opt_newNode?: ASTNode) {
-    let workspaceId = opt_block ? opt_block.workspace!.id : undefined;
+    let workspaceId = opt_block ? opt_block.workspace.id : undefined;
     if (opt_newNode && opt_newNode.getType() === ASTNode.types.WORKSPACE) {
       workspaceId = (opt_newNode.getLocation() as Workspace).id;
     }
diff --git a/core/events/events_ui.ts b/core/events/events_ui.ts
index f77fe7ee34e..de647f2fb40 100644
--- a/core/events/events_ui.ts
+++ b/core/events/events_ui.ts
@@ -46,7 +46,7 @@ export class Ui extends UiBase {
   constructor(
       opt_block?: Block|null, opt_element?: string,
       opt_oldValue?: AnyDuringMigration, opt_newValue?: AnyDuringMigration) {
-    const workspaceId = opt_block ? opt_block.workspace!.id : undefined;
+    const workspaceId = opt_block ? opt_block.workspace.id : undefined;
     super(workspaceId);
 
     this.blockId = opt_block ? opt_block.id : null;
diff --git a/core/field.ts b/core/field.ts
index 0654411ed9f..8f4fa456d12 100644
--- a/core/field.ts
+++ b/core/field.ts
@@ -264,7 +264,7 @@ export abstract class Field implements IASTNodeLocationSvg,
    * @return The renderer constant provider.
    */
   getConstants(): ConstantProvider|null {
-    if (!this.constants_ && this.sourceBlock_ && this.sourceBlock_.workspace &&
+    if (!this.constants_ && this.sourceBlock_ && !this.sourceBlock_.disposed &&
         this.sourceBlock_.workspace.rendered) {
       this.constants_ = (this.sourceBlock_.workspace as WorkspaceSvg)
                             .getRenderer()
@@ -1023,7 +1023,7 @@ export abstract class Field implements IASTNodeLocationSvg,
    * @param e Mouse down event.
    */
   protected onMouseDown_(e: Event) {
-    if (!this.sourceBlock_ || !this.sourceBlock_.workspace) {
+    if (!this.sourceBlock_ || this.sourceBlock_.disposed) {
       return;
     }
     const gesture = (this.sourceBlock_.workspace as WorkspaceSvg).getGesture(e);
diff --git a/core/field_variable.ts b/core/field_variable.ts
index 4b510af7e16..39fe3f3ba04 100644
--- a/core/field_variable.ts
+++ b/core/field_variable.ts
@@ -139,7 +139,7 @@ export class FieldVariable extends FieldDropdown {
       return;  // Initialization already happened.
     }
     const variable = Variables.getOrCreateVariablePackage(
-        this.sourceBlock_.workspace!, null, this.defaultVariableName,
+        this.sourceBlock_.workspace, null, this.defaultVariableName,
         this.defaultType_);
     // Don't call setValue because we don't want to cause a rerender.
     this.doValueUpdate_(variable.getId());
@@ -167,7 +167,7 @@ export class FieldVariable extends FieldDropdown {
     // AnyDuringMigration because:  Argument of type 'string | null' is not
     // assignable to parameter of type 'string | undefined'.
     const variable = Variables.getOrCreateVariablePackage(
-        this.sourceBlock_.workspace!, id, variableName as AnyDuringMigration,
+        this.sourceBlock_.workspace, id, variableName as AnyDuringMigration,
         variableType);
 
     // This should never happen :)
@@ -234,7 +234,7 @@ export class FieldVariable extends FieldDropdown {
     }
     // This is necessary so that blocks in the flyout can have custom var names.
     const variable = Variables.getOrCreateVariablePackage(
-        this.sourceBlock_.workspace!, state['id'] || null, state['name'],
+        this.sourceBlock_.workspace, state['id'] || null, state['name'],
         state['type'] || '');
     this.setValue(variable.getId());
   }
@@ -306,7 +306,7 @@ export class FieldVariable extends FieldDropdown {
       return null;
     }
     const newId = opt_newValue as string;
-    const variable = Variables.getVariable(this.sourceBlock_.workspace!, newId);
+    const variable = Variables.getVariable(this.sourceBlock_.workspace, newId);
     if (!variable) {
       console.warn(
           'Variable id doesn\'t point to a real variable! ' +
@@ -332,7 +332,7 @@ export class FieldVariable extends FieldDropdown {
    */
   protected override doValueUpdate_(newId: AnyDuringMigration) {
     this.variable_ =
-        Variables.getVariable(this.sourceBlock_.workspace!, newId as string);
+        Variables.getVariable(this.sourceBlock_.workspace, newId as string);
     super.doValueUpdate_(newId);
   }
 
@@ -364,7 +364,7 @@ export class FieldVariable extends FieldDropdown {
     let variableTypes = this.variableTypes;
     if (variableTypes === null) {
       // If variableTypes is null, return all variable types.
-      if (this.sourceBlock_ && this.sourceBlock_.workspace) {
+      if (this.sourceBlock_ && !this.sourceBlock_.disposed) {
         return this.sourceBlock_.workspace.getVariableTypes();
       }
     }
@@ -440,7 +440,7 @@ export class FieldVariable extends FieldDropdown {
   protected override onItemSelected_(menu: Menu, menuItem: MenuItem) {
     const id = menuItem.getValue();
     // Handle special cases.
-    if (this.sourceBlock_ && this.sourceBlock_.workspace) {
+    if (this.sourceBlock_ && !this.sourceBlock_.disposed) {
       if (id === internalConstants.RENAME_VARIABLE_ID) {
         // Rename variable.
         Variables.renameVariable(
@@ -495,7 +495,7 @@ export class FieldVariable extends FieldDropdown {
     }
     const name = this.getText();
     let variableModelList: AnyDuringMigration[] = [];
-    if (this.sourceBlock_ && this.sourceBlock_.workspace) {
+    if (this.sourceBlock_ && !this.sourceBlock_.disposed) {
       const variableTypes = this.getVariableTypes_();
       // Get a copy of the list, so that adding rename and new variable options
       // doesn't modify the workspace's list.
diff --git a/core/gesture.ts b/core/gesture.ts
index 053ea396f4e..5d9ff2604a0 100644
--- a/core/gesture.ts
+++ b/core/gesture.ts
@@ -581,7 +581,7 @@ export class Gesture {
   handleRightClick(e: Event) {
     if (this.targetBlock_) {
       this.bringBlockToFront_();
-      this.targetBlock_.workspace!.hideChaff(!!this.flyout_);
+      this.targetBlock_.workspace.hideChaff(!!this.flyout_);
       this.targetBlock_.showContextMenu(e);
     } else if (this.startBubble_) {
       this.startBubble_.showContextMenu(e);
diff --git a/core/icon.ts b/core/icon.ts
index c74028acb81..6cf57f2a9b6 100644
--- a/core/icon.ts
+++ b/core/icon.ts
@@ -111,7 +111,7 @@ export abstract class Icon {
    * @param e Mouse click event.
    */
   protected iconClick_(e: Event) {
-    if (this.block_.workspace!.isDragging()) {
+    if (this.block_.workspace.isDragging()) {
       // Drag operation is concluding.  Don't open the editor.
       return;
     }
diff --git a/core/input.ts b/core/input.ts
index 079366cb889..4d58cc2f064 100644
--- a/core/input.ts
+++ b/core/input.ts
@@ -271,7 +271,7 @@ export class Input {
 
   /** Initialize the fields on this input. */
   init() {
-    if (!this.sourceBlock_.workspace!.rendered) {
+    if (!this.sourceBlock_.workspace.rendered) {
       return;  // Headless blocks don't need fields initialized.
     }
     for (let i = 0; i < this.fieldRow.length; i++) {
diff --git a/core/insertion_marker_manager.ts b/core/insertion_marker_manager.ts
index 1f8941fa6ac..abdfca4dea3 100644
--- a/core/insertion_marker_manager.ts
+++ b/core/insertion_marker_manager.ts
@@ -133,7 +133,7 @@ export class InsertionMarkerManager {
      * The workspace on which these connections are being dragged.
      * Does not change during a drag.
      */
-    this.workspace_ = block.workspace!;
+    this.workspace_ = block.workspace;
 
     /**
      * The insertion marker that shows up between blocks to show where a block
diff --git a/core/keyboard_nav/ast_node.ts b/core/keyboard_nav/ast_node.ts
index 4efe194dbb6..45cd785e35f 100644
--- a/core/keyboard_nav/ast_node.ts
+++ b/core/keyboard_nav/ast_node.ts
@@ -268,11 +268,11 @@ export class ASTNode {
     // TODO(#6097): Use instanceof checks to exit early for values of
     // curLocation that don't make sense.
     const curLocationAsBlock = curLocation as Block;
-    if (!curLocationAsBlock || !curLocationAsBlock.workspace) {
+    if (!curLocationAsBlock || curLocationAsBlock.disposed) {
       return null;
     }
     const curRoot = curLocationAsBlock.getRootBlock();
-    const topBlocks = curRoot.workspace?.getTopBlocks(true) ?? [];
+    const topBlocks = curRoot.workspace.getTopBlocks(true);
     for (let i = 0; i < topBlocks.length; i++) {
       const topBlock = topBlocks[i];
       if (curRoot.id === topBlock.id) {
diff --git a/core/mutator.ts b/core/mutator.ts
index aff6f8bf02b..1201e06300c 100644
--- a/core/mutator.ts
+++ b/core/mutator.ts
@@ -178,11 +178,11 @@ export class Mutator extends Icon {
       // event filter from workspaceChanged_ .
       'disable': false,
       'parentWorkspace': this.block_.workspace,
-      'media': this.block_.workspace!.options.pathToMedia,
+      'media': this.block_.workspace.options.pathToMedia,
       'rtl': this.block_.RTL,
       'horizontalLayout': false,
-      'renderer': this.block_.workspace!.options.renderer,
-      'rendererOverrides': this.block_.workspace!.options.rendererOverrides,
+      'renderer': this.block_.workspace.options.renderer,
+      'rendererOverrides': this.block_.workspace.options.rendererOverrides,
     } as BlocklyOptions));
     workspaceOptions.toolboxPosition =
         this.block_.RTL ? toolbox.Position.RIGHT : toolbox.Position.LEFT;
@@ -353,7 +353,7 @@ export class Mutator extends Icon {
             this.block_.saveConnections(thisRootBlock);
           }
         };
-        this.block_.workspace!.addChangeListener(this.sourceListener_);
+        this.block_.workspace.addChangeListener(this.sourceListener_);
       }
       this.resizeBubble_();
       // When the mutator's workspace changes, update the source block.
@@ -372,7 +372,7 @@ export class Mutator extends Icon {
       this.workspaceWidth_ = 0;
       this.workspaceHeight_ = 0;
       if (this.sourceListener_) {
-        this.block_.workspace!.removeChangeListener(this.sourceListener_);
+        this.block_.workspace.removeChangeListener(this.sourceListener_);
         this.sourceListener_ = null;
       }
     }
diff --git a/core/procedures.ts b/core/procedures.ts
index 4e152c3c7b3..f5ac72f7317 100644
--- a/core/procedures.ts
+++ b/core/procedures.ts
@@ -111,7 +111,7 @@ export function findLegalName(name: string, block: Block): string {
     return name;
   }
   name = name || Msg['UNNAMED_KEY'] || 'unnamed';
-  while (!isLegalName(name, block.workspace!, block)) {
+  while (!isLegalName(name, block.workspace, block)) {
     // Collision with another procedure.
     const r = name.match(/^(.*?)(\d+)$/);
     if (!r) {
@@ -179,7 +179,7 @@ export function rename(this: Field, name: string): string {
   const oldName = this.getValue();
   if (oldName !== name && oldName !== legalName) {
     // Rename any callers.
-    const blocks = this.getSourceBlock().workspace!.getAllBlocks(false);
+    const blocks = this.getSourceBlock().workspace.getAllBlocks(false);
     for (let i = 0; i < blocks.length; i++) {
       // Assume it is a procedure so we can check.
       const procedureBlock = blocks[i] as unknown as ProcedureBlock;
@@ -396,7 +396,7 @@ export function mutateCallers(defBlock: Block) {
   const procedureBlock = defBlock as unknown as ProcedureBlock;
   const name = procedureBlock.getProcedureDef()[0];
   const xmlElement = defBlock.mutationToDom!(true);
-  const callers = getCallers(name, defBlock.workspace!);
+  const callers = getCallers(name, defBlock.workspace);
   for (let i = 0, caller; caller = callers[i]; i++) {
     const oldMutationDom = caller.mutationToDom!();
     const oldMutation = oldMutationDom && Xml.domToText(oldMutationDom);
diff --git a/core/rendered_connection.ts b/core/rendered_connection.ts
index 0689dfe2b8f..430bc89e02e 100644
--- a/core/rendered_connection.ts
+++ b/core/rendered_connection.ts
@@ -70,14 +70,14 @@ export class RenderedConnection extends Connection {
      * Connection database for connections of this type on the current
      * workspace.
      */
-    this.db_ = source.workspace!.connectionDBList[type];
+    this.db_ = source.workspace.connectionDBList[type];
 
     /**
      * Connection database for connections compatible with this type on the
      * current workspace.
      */
     this.dbOpposite_ =
-        source.workspace!
+        source.workspace
             .connectionDBList[internalConstants.OPPOSITE_TYPE[type]];
 
     /** Workspace units, (0, 0) is top left of block. */
@@ -134,7 +134,7 @@ export class RenderedConnection extends Connection {
    * @internal
    */
   bumpAwayFrom(staticConnection: RenderedConnection) {
-    if (this.sourceBlock_.workspace!.isDragging()) {
+    if (this.sourceBlock_.workspace.isDragging()) {
       // Don't move blocks around while the user is doing the same.
       return;
     }
@@ -271,7 +271,7 @@ export class RenderedConnection extends Connection {
     let steps;
     const sourceBlockSvg = (this.sourceBlock_);
     const renderConstants =
-        sourceBlockSvg.workspace!.getRenderer().getConstants();
+        sourceBlockSvg.workspace.getRenderer().getConstants();
     const shape = renderConstants.shapeFor(this);
     if (this.type === ConnectionType.INPUT_VALUE ||
         this.type === ConnectionType.OUTPUT_VALUE) {
diff --git a/core/serialization/blocks.ts b/core/serialization/blocks.ts
index 8b57aa17a07..5f2f03f77e8 100644
--- a/core/serialization/blocks.ts
+++ b/core/serialization/blocks.ts
@@ -162,7 +162,7 @@ function saveAttributes(block: Block, state: State) {
  * @param state The state object to append to.
  */
 function saveCoords(block: Block, state: State) {
-  const workspace = block.workspace!;
+  const workspace = block.workspace;
   const xy = block.getRelativeToSurfaceXY();
   state['x'] = Math.round(workspace.RTL ? workspace.getWidth() - xy.x : xy.x);
   state['y'] = Math.round(xy.y);
@@ -416,7 +416,7 @@ function loadCoords(block: Block, state: State) {
   let x = state['x'] === undefined ? 0 : state['x'];
   const y = state['y'] === undefined ? 0 : state['y'];
 
-  const workspace = block.workspace!;
+  const workspace = block.workspace;
   x = workspace.RTL ? workspace.getWidth() - x : x;
 
   block.moveBy(x, y);
@@ -492,7 +492,7 @@ function tryToConnectParent(
   }
 
   if (!connected) {
-    const checker = child.workspace!.connectionChecker;
+    const checker = child.workspace.connectionChecker;
     throw new BadConnectionCheck(
         checker.getErrorMessage(
             checker.canConnectWithReason(
@@ -606,7 +606,7 @@ function loadConnection(
   }
   if (connectionState['block']) {
     appendPrivate(
-        connectionState['block'], connection.getSourceBlock().workspace!,
+        connectionState['block'], connection.getSourceBlock().workspace,
         {parentConnection: connection});
   }
 }
diff --git a/core/shortcut_items.ts b/core/shortcut_items.ts
index 072da602e15..dfdeb0f1c35 100644
--- a/core/shortcut_items.ts
+++ b/core/shortcut_items.ts
@@ -142,7 +142,7 @@ export function registerCut() {
       return !!(
           !workspace.options.readOnly && !Gesture.inProgress() && selected &&
           selected instanceof BlockSvg && selected.isDeletable() &&
-          selected.isMovable() && !selected.workspace!.isFlyout);
+          selected.isMovable() && !selected.workspace.isFlyout);
     },
     callback() {
       const selected = common.getSelected();
diff --git a/core/xml.ts b/core/xml.ts
index 414b8e54e14..677b9edf6aa 100644
--- a/core/xml.ts
+++ b/core/xml.ts
@@ -109,7 +109,7 @@ export function blockToDomWithXY(block: Block, opt_noId?: boolean): Element|
   }
 
   let width = 0;  // Not used in LTR.
-  if (block.workspace?.RTL) {
+  if (block.workspace.RTL) {
     width = block.workspace.getWidth();
   }
 
@@ -118,8 +118,7 @@ export function blockToDomWithXY(block: Block, opt_noId?: boolean): Element|
   // AnyDuringMigration because:  Property 'setAttribute' does not exist on type
   // 'Element | DocumentFragment'.
   (element as AnyDuringMigration)
-      .setAttribute(
-          'x', Math.round(block.workspace?.RTL ? width - xy.x : xy.x));
+      .setAttribute('x', Math.round(block.workspace.RTL ? width - xy.x : xy.x));
   // AnyDuringMigration because:  Property 'setAttribute' does not exist on type
   // 'Element | DocumentFragment'.
   (element as AnyDuringMigration).setAttribute('y', Math.round(xy.y));