refactor: Convert renderer typecheck methods to typeguards. (#8656)

* refactor: Convert renderer typecheck methods to typeguards.

* chore: Revert unintended change.

* chore: Format types.ts.

core/renderers/common/drawer.ts

@@ -15,7 +15,6 @@ import type {ExternalValueInput} from '../measurables/external_value_input.js';
 import type {Field} from '../measurables/field.js';
 import type {Icon} from '../measurables/icon.js';
 import type {InlineInput} from '../measurables/inline_input.js';
-import type {PreviousConnection} from '../measurables/previous_connection.js';
 import type {Row} from '../measurables/row.js';
 import {Types} from '../measurables/types.js';
 import type {ConstantProvider, Notch, PuzzleTab} from './constants.js';
@@ -116,13 +115,8 @@ export class Drawer {
         this.outlinePath_ += this.constants_.OUTSIDE_CORNERS.topLeft;
       } else if (Types.isRightRoundedCorner(elem)) {
         this.outlinePath_ += this.constants_.OUTSIDE_CORNERS.topRight;
-      } else if (
-        Types.isPreviousConnection(elem) &&
-        elem instanceof Connection
-      ) {
-        this.outlinePath_ += (
-          (elem as PreviousConnection).shape as Notch
-        ).pathLeft;
+      } else if (Types.isPreviousConnection(elem)) {
+        this.outlinePath_ += (elem.shape as Notch).pathLeft;
       } else if (Types.isHat(elem)) {
         this.outlinePath_ += this.constants_.START_HAT.path;
       } else if (Types.isSpacer(elem)) {
@@ -217,7 +211,7 @@ export class Drawer {
     let rightCornerYOffset = 0;
     let outlinePath = '';
     for (let i = elems.length - 1, elem; (elem = elems[i]); i--) {
-      if (Types.isNextConnection(elem) && elem instanceof Connection) {
+      if (Types.isNextConnection(elem)) {
         outlinePath += (elem.shape as Notch).pathRight;
       } else if (Types.isLeftSquareCorner(elem)) {
         outlinePath += svgPaths.lineOnAxis('H', bottomRow.xPos);
@@ -269,9 +263,9 @@ export class Drawer {
     for (let i = 0, row; (row = this.info_.rows[i]); i++) {
       for (let j = 0, elem; (elem = row.elements[j]); j++) {
         if (Types.isInlineInput(elem)) {
-          this.drawInlineInput_(elem as InlineInput);
+          this.drawInlineInput_(elem);
         } else if (Types.isIcon(elem) || Types.isField(elem)) {
-          this.layoutField_(elem as Field | Icon);
+          this.layoutField_(elem);
         }
       }
     }
@@ -295,13 +289,13 @@ export class Drawer {
     }
 
     if (Types.isIcon(fieldInfo)) {
-      const icon = (fieldInfo as Icon).icon;
+      const icon = fieldInfo.icon;
       icon.setOffsetInBlock(new Coordinate(xPos, yPos));
       if (this.info_.isInsertionMarker) {
         icon.hideForInsertionMarker();
       }
     } else {
-      const svgGroup = (fieldInfo as Field).field.getSvgRoot()!;
+      const svgGroup = fieldInfo.field.getSvgRoot()!;
       svgGroup.setAttribute(
         'transform',
         'translate(' + xPos + ',' + yPos + ')' + scale,

core/renderers/common/info.ts

@@ -671,20 +671,17 @@ export class RenderInfo {
       return row.yPos + elem.height / 2;
     }
     if (Types.isBottomRow(row)) {
-      const bottomRow = row as BottomRow;
-      const baseline =
-        bottomRow.yPos + bottomRow.height - bottomRow.descenderHeight;
+      const baseline = row.yPos + row.height - row.descenderHeight;
       if (Types.isNextConnection(elem)) {
         return baseline + elem.height / 2;
       }
       return baseline - elem.height / 2;
     }
     if (Types.isTopRow(row)) {
-      const topRow = row as TopRow;
       if (Types.isHat(elem)) {
-        return topRow.capline - elem.height / 2;
+        return row.capline - elem.height / 2;
       }
-      return topRow.capline + elem.height / 2;
+      return row.capline + elem.height / 2;
     }
     return row.yPos + row.height / 2;
   }

core/renderers/geras/drawer.ts

@@ -100,7 +100,7 @@ export class Drawer extends BaseDrawer {
   }
 
   override drawInlineInput_(input: InlineInput) {
-    this.highlighter_.drawInlineInput(input as InlineInput);
+    this.highlighter_.drawInlineInput(input);
 
     super.drawInlineInput_(input);
   }

core/renderers/geras/info.ts

@@ -14,13 +14,9 @@ import {StatementInput} from '../../inputs/statement_input.js';
 import {ValueInput} from '../../inputs/value_input.js';
 import {RenderInfo as BaseRenderInfo} from '../common/info.js';
 import type {Measurable} from '../measurables/base.js';
-import type {BottomRow} from '../measurables/bottom_row.js';
 import {ExternalValueInput} from '../measurables/external_value_input.js';
-import type {Field} from '../measurables/field.js';
 import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import type {InputRow} from '../measurables/input_row.js';
 import type {Row} from '../measurables/row.js';
-import type {TopRow} from '../measurables/top_row.js';
 import {Types} from '../measurables/types.js';
 import type {ConstantProvider} from './constants.js';
 import {InlineInput} from './measurables/inline_input.js';
@@ -150,7 +146,7 @@ export class RenderInfo extends BaseRenderInfo {
   override getInRowSpacing_(prev: Measurable | null, next: Measurable | null) {
     if (!prev) {
       // Between an editable field and the beginning of the row.
-      if (next && Types.isField(next) && (next as Field).isEditable) {
+      if (next && Types.isField(next) && next.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       }
       // Inline input at the beginning of the row.
@@ -167,7 +163,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between a non-input and the end of the row or a statement input.
     if (!Types.isInput(prev) && (!next || Types.isStatementInput(next))) {
       // Between an editable field and the end of the row.
-      if (Types.isField(prev) && (prev as Field).isEditable) {
+      if (Types.isField(prev) && prev.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       }
       // Padding at the end of an icon-only row to make the block shape clearer.
@@ -208,7 +204,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between a non-input and an input.
     if (!Types.isInput(prev) && next && Types.isInput(next)) {
       // Between an editable field and an input.
-      if (Types.isField(prev) && (prev as Field).isEditable) {
+      if (Types.isField(prev) && prev.isEditable) {
         if (Types.isInlineInput(next)) {
           return this.constants_.SMALL_PADDING;
         } else if (Types.isExternalInput(next)) {
@@ -233,7 +229,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between an inline input and a field.
     if (Types.isInlineInput(prev) && next && Types.isField(next)) {
       // Editable field after inline input.
-      if ((next as Field).isEditable) {
+      if (next.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       } else {
         // Noneditable field after inline input.
@@ -278,7 +274,7 @@ export class RenderInfo extends BaseRenderInfo {
       Types.isField(prev) &&
       next &&
       Types.isField(next) &&
-      (prev as Field).isEditable === (next as Field).isEditable
+      prev.isEditable === next.isEditable
     ) {
       return this.constants_.LARGE_PADDING;
     }
@@ -323,20 +319,17 @@ export class RenderInfo extends BaseRenderInfo {
       return row.yPos + elem.height / 2;
     }
     if (Types.isBottomRow(row)) {
-      const bottomRow = row as BottomRow;
-      const baseline =
-        bottomRow.yPos + bottomRow.height - bottomRow.descenderHeight;
+      const baseline = row.yPos + row.height - row.descenderHeight;
       if (Types.isNextConnection(elem)) {
         return baseline + elem.height / 2;
       }
       return baseline - elem.height / 2;
     }
     if (Types.isTopRow(row)) {
-      const topRow = row as TopRow;
       if (Types.isHat(elem)) {
-        return topRow.capline - elem.height / 2;
+        return row.capline - elem.height / 2;
       }
-      return topRow.capline + elem.height / 2;
+      return row.capline + elem.height / 2;
     }
 
     let result = row.yPos;
@@ -370,7 +363,7 @@ export class RenderInfo extends BaseRenderInfo {
       rowNextRightEdges.set(row, nextRightEdge);
       if (Types.isInputRow(row)) {
         if (row.hasStatement) {
-          this.alignStatementRow_(row as InputRow);
+          this.alignStatementRow_(row);
         }
         if (
           prevInput &&

core/renderers/measurables/in_row_spacer.ts

@@ -15,6 +15,14 @@ import {Types} from './types.js';
  * row.
  */
 export class InRowSpacer extends Measurable {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private inRowSpacer: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param width The width of the spacer.

core/renderers/measurables/input_row.ts

@@ -7,10 +7,7 @@
 // Former goog.module ID: Blockly.blockRendering.InputRow
 
 import type {ConstantProvider} from '../common/constants.js';
-import {ExternalValueInput} from './external_value_input.js';
-import {InputConnection} from './input_connection.js';
 import {Row} from './row.js';
-import {StatementInput} from './statement_input.js';
 import {Types} from './types.js';
 
 /**
@@ -40,12 +37,11 @@ export class InputRow extends Row {
     for (let i = 0; i < this.elements.length; i++) {
       const elem = this.elements[i];
       this.width += elem.width;
-      if (Types.isInput(elem) && elem instanceof InputConnection) {
-        if (Types.isStatementInput(elem) && elem instanceof StatementInput) {
+      if (Types.isInput(elem)) {
+        if (Types.isStatementInput(elem)) {
           connectedBlockWidths += elem.connectedBlockWidth;
         } else if (
           Types.isExternalInput(elem) &&
-          elem instanceof ExternalValueInput &&
           elem.connectedBlockWidth !== 0
         ) {
           connectedBlockWidths +=

core/renderers/measurables/jagged_edge.ts

@@ -15,6 +15,14 @@ import {Types} from './types.js';
  * collapsed block takes up during rendering.
  */
 export class JaggedEdge extends Measurable {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private jaggedEdge: undefined;
+
   /**
    * @param constants The rendering constants provider.
    */

core/renderers/measurables/next_connection.ts

@@ -16,6 +16,14 @@ import {Types} from './types.js';
  * up during rendering.
  */
 export class NextConnection extends Connection {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private nextConnection: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param connectionModel The connection object on the block that this

core/renderers/measurables/previous_connection.ts

@@ -16,6 +16,14 @@ import {Types} from './types.js';
  * up during rendering.
  */
 export class PreviousConnection extends Connection {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private previousConnection: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param connectionModel The connection object on the block that this

core/renderers/measurables/round_corner.ts

@@ -15,6 +15,14 @@ import {Types} from './types.js';
  * during rendering.
  */
 export class RoundCorner extends Measurable {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private roundCorner: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param opt_position The position of this corner.

core/renderers/measurables/row.ts

@@ -127,7 +127,7 @@ export class Row {
     for (let i = this.elements.length - 1; i >= 0; i--) {
       const elem = this.elements[i];
       if (Types.isInput(elem)) {
-        return elem as InputConnection;
+        return elem;
       }
     }
     return null;
@@ -166,8 +166,8 @@ export class Row {
   getFirstSpacer(): InRowSpacer | null {
     for (let i = 0; i < this.elements.length; i++) {
       const elem = this.elements[i];
-      if (Types.isSpacer(elem)) {
-        return elem as InRowSpacer;
+      if (Types.isInRowSpacer(elem)) {
+        return elem;
       }
     }
     return null;
@@ -181,8 +181,8 @@ export class Row {
   getLastSpacer(): InRowSpacer | null {
     for (let i = this.elements.length - 1; i >= 0; i--) {
       const elem = this.elements[i];
-      if (Types.isSpacer(elem)) {
-        return elem as InRowSpacer;
+      if (Types.isInRowSpacer(elem)) {
+        return elem;
       }
     }
     return null;

core/renderers/measurables/square_corner.ts

@@ -15,6 +15,14 @@ import {Types} from './types.js';
  * during rendering.
  */
 export class SquareCorner extends Measurable {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private squareCorner: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param opt_position The position of this corner.

core/renderers/measurables/statement_input.ts

@@ -16,6 +16,14 @@ import {Types} from './types.js';
  * during rendering
  */
 export class StatementInput extends InputConnection {
+  // This field exists solely to structurally distinguish this type from other
+  // Measurable subclasses. Because this class otherwise has the same fields as
+  // Measurable, and Typescript doesn't support nominal typing, Typescript will
+  // consider it and other subclasses in the same situation as being of the same
+  // type, even if typeguards are used, which could result in Typescript typing
+  // objects of this class as `never`.
+  private statementInput: undefined;
+
   /**
    * @param constants The rendering constants provider.
    * @param input The statement input to measure and store information for.

core/renderers/measurables/top_row.ts

@@ -8,7 +8,6 @@
 
 import type {BlockSvg} from '../../block_svg.js';
 import type {ConstantProvider} from '../common/constants.js';
-import {Hat} from './hat.js';
 import type {PreviousConnection} from './previous_connection.js';
 import {Row} from './row.js';
 import {Types} from './types.js';
@@ -85,7 +84,7 @@ export class TopRow extends Row {
       const elem = this.elements[i];
       width += elem.width;
       if (!Types.isSpacer(elem)) {
-        if (Types.isHat(elem) && elem instanceof Hat) {
+        if (Types.isHat(elem)) {
           ascenderHeight = Math.max(ascenderHeight, elem.ascenderHeight);
         } else {
           height = Math.max(height, elem.height);

core/renderers/measurables/types.ts

@@ -7,7 +7,24 @@
 // Former goog.module ID: Blockly.blockRendering.Types
 
 import type {Measurable} from './base.js';
+import type {BottomRow} from './bottom_row.js';
+import type {ExternalValueInput} from './external_value_input.js';
+import type {Field} from './field.js';
+import type {Hat} from './hat.js';
+import type {Icon} from './icon.js';
+import type {InRowSpacer} from './in_row_spacer.js';
+import type {InlineInput} from './inline_input.js';
+import type {InputConnection} from './input_connection.js';
+import type {InputRow} from './input_row.js';
+import type {JaggedEdge} from './jagged_edge.js';
+import type {NextConnection} from './next_connection.js';
+import type {PreviousConnection} from './previous_connection.js';
+import type {RoundCorner} from './round_corner.js';
 import type {Row} from './row.js';
+import type {SpacerRow} from './spacer_row.js';
+import type {SquareCorner} from './square_corner.js';
+import type {StatementInput} from './statement_input.js';
+import type {TopRow} from './top_row.js';
 
 /**
  * Types of rendering elements.
@@ -82,8 +99,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a field.
    */
-  isField(elem: Measurable): number {
-    return elem.type & this.FIELD;
+  isField(elem: Measurable): elem is Field {
+    return (elem.type & this.FIELD) >= 1;
   }
 
   /**
@@ -92,8 +109,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a hat.
    */
-  isHat(elem: Measurable): number {
-    return elem.type & this.HAT;
+  isHat(elem: Measurable): elem is Hat {
+    return (elem.type & this.HAT) >= 1;
   }
 
   /**
@@ -102,8 +119,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about an icon.
    */
-  isIcon(elem: Measurable): number {
-    return elem.type & this.ICON;
+  isIcon(elem: Measurable): elem is Icon {
+    return (elem.type & this.ICON) >= 1;
   }
 
   /**
@@ -112,8 +129,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a spacer.
    */
-  isSpacer(elem: Measurable | Row): number {
-    return elem.type & this.SPACER;
+  isSpacer(elem: Measurable | Row): elem is SpacerRow | InRowSpacer {
+    return (elem.type & this.SPACER) >= 1;
   }
 
   /**
@@ -122,8 +139,18 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about an in-row spacer.
    */
-  isInRowSpacer(elem: Measurable): number {
-    return elem.type & this.IN_ROW_SPACER;
+  isInRowSpacer(elem: Measurable): elem is InRowSpacer {
+    return (elem.type & this.IN_ROW_SPACER) >= 1;
+  }
+
+  /**
+   * Whether a row is a spacer row.
+   *
+   * @param row The row to check.
+   * @returns True if the row is a spacer row.
+   */
+  isSpacerRow(row: Row): row is SpacerRow {
+    return (row.type & this.BETWEEN_ROW_SPACER) >= 1;
   }
 
   /**
@@ -132,8 +159,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about an input.
    */
-  isInput(elem: Measurable): number {
-    return elem.type & this.INPUT;
+  isInput(elem: Measurable): elem is InputConnection {
+    return (elem.type & this.INPUT) >= 1;
   }
 
   /**
@@ -142,8 +169,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about an external input.
    */
-  isExternalInput(elem: Measurable): number {
-    return elem.type & this.EXTERNAL_VALUE_INPUT;
+  isExternalInput(elem: Measurable): elem is ExternalValueInput {
+    return (elem.type & this.EXTERNAL_VALUE_INPUT) >= 1;
   }
 
   /**
@@ -152,8 +179,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about an inline input.
    */
-  isInlineInput(elem: Measurable): number {
-    return elem.type & this.INLINE_INPUT;
+  isInlineInput(elem: Measurable): elem is InlineInput {
+    return (elem.type & this.INLINE_INPUT) >= 1;
   }
 
   /**
@@ -162,8 +189,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a statement input.
    */
-  isStatementInput(elem: Measurable): number {
-    return elem.type & this.STATEMENT_INPUT;
+  isStatementInput(elem: Measurable): elem is StatementInput {
+    return (elem.type & this.STATEMENT_INPUT) >= 1;
   }
 
   /**
@@ -172,8 +199,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a previous connection.
    */
-  isPreviousConnection(elem: Measurable): number {
-    return elem.type & this.PREVIOUS_CONNECTION;
+  isPreviousConnection(elem: Measurable): elem is PreviousConnection {
+    return (elem.type & this.PREVIOUS_CONNECTION) >= 1;
   }
 
   /**
@@ -182,8 +209,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a next connection.
    */
-  isNextConnection(elem: Measurable): number {
-    return elem.type & this.NEXT_CONNECTION;
+  isNextConnection(elem: Measurable): elem is NextConnection {
+    return (elem.type & this.NEXT_CONNECTION) >= 1;
   }
 
   /**
@@ -194,8 +221,17 @@ class TypesContainer {
    * @returns 1 if the object stores information about a previous or next
    *     connection.
    */
-  isPreviousOrNextConnection(elem: Measurable): number {
-    return elem.type & (this.PREVIOUS_CONNECTION | this.NEXT_CONNECTION);
+  isPreviousOrNextConnection(
+    elem: Measurable,
+  ): elem is PreviousConnection | NextConnection {
+    return this.isPreviousConnection(elem) || this.isNextConnection(elem);
+  }
+
+  isRoundCorner(elem: Measurable): elem is RoundCorner {
+    return (
+      (elem.type & this.LEFT_ROUND_CORNER) >= 1 ||
+      (elem.type & this.RIGHT_ROUND_CORNER) >= 1
+    );
   }
 
   /**
@@ -204,8 +240,10 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a left round corner.
    */
-  isLeftRoundedCorner(elem: Measurable): number {
-    return elem.type & this.LEFT_ROUND_CORNER;
+  isLeftRoundedCorner(elem: Measurable): boolean {
+    return (
+      this.isRoundCorner(elem) && (elem.type & this.LEFT_ROUND_CORNER) >= 1
+    );
   }
 
   /**
@@ -214,8 +252,10 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a right round corner.
    */
-  isRightRoundedCorner(elem: Measurable): number {
-    return elem.type & this.RIGHT_ROUND_CORNER;
+  isRightRoundedCorner(elem: Measurable): boolean {
+    return (
+      this.isRoundCorner(elem) && (elem.type & this.RIGHT_ROUND_CORNER) >= 1
+    );
   }
 
   /**
@@ -224,8 +264,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a left square corner.
    */
-  isLeftSquareCorner(elem: Measurable): number {
-    return elem.type & this.LEFT_SQUARE_CORNER;
+  isLeftSquareCorner(elem: Measurable): boolean {
+    return (elem.type & this.LEFT_SQUARE_CORNER) >= 1;
   }
 
   /**
@@ -234,8 +274,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a right square corner.
    */
-  isRightSquareCorner(elem: Measurable): number {
-    return elem.type & this.RIGHT_SQUARE_CORNER;
+  isRightSquareCorner(elem: Measurable): boolean {
+    return (elem.type & this.RIGHT_SQUARE_CORNER) >= 1;
   }
 
   /**
@@ -244,8 +284,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a corner.
    */
-  isCorner(elem: Measurable): number {
-    return elem.type & this.CORNER;
+  isCorner(elem: Measurable): elem is SquareCorner | RoundCorner {
+    return (elem.type & this.CORNER) >= 1;
   }
 
   /**
@@ -254,8 +294,8 @@ class TypesContainer {
    * @param elem The element to check.
    * @returns 1 if the object stores information about a jagged edge.
    */
-  isJaggedEdge(elem: Measurable): number {
-    return elem.type & this.JAGGED_EDGE;
+  isJaggedEdge(elem: Measurable): elem is JaggedEdge {
+    return (elem.type & this.JAGGED_EDGE) >= 1;
   }
 
   /**
@@ -264,8 +304,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about a row.
    */
-  isRow(row: Row): number {
-    return row.type & this.ROW;
+  isRow(row: Row): row is Row {
+    return (row.type & this.ROW) >= 1;
   }
 
   /**
@@ -274,8 +314,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about a between-row spacer.
    */
-  isBetweenRowSpacer(row: Row): number {
-    return row.type & this.BETWEEN_ROW_SPACER;
+  isBetweenRowSpacer(row: Row): row is SpacerRow {
+    return (row.type & this.BETWEEN_ROW_SPACER) >= 1;
   }
 
   /**
@@ -284,8 +324,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about a top row.
    */
-  isTopRow(row: Row): number {
-    return row.type & this.TOP_ROW;
+  isTopRow(row: Row): row is TopRow {
+    return (row.type & this.TOP_ROW) >= 1;
   }
 
   /**
@@ -294,8 +334,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about a bottom row.
    */
-  isBottomRow(row: Row): number {
-    return row.type & this.BOTTOM_ROW;
+  isBottomRow(row: Row): row is BottomRow {
+    return (row.type & this.BOTTOM_ROW) >= 1;
   }
 
   /**
@@ -304,8 +344,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about a top or bottom row.
    */
-  isTopOrBottomRow(row: Row): number {
-    return row.type & (this.TOP_ROW | this.BOTTOM_ROW);
+  isTopOrBottomRow(row: Row): row is TopRow | BottomRow {
+    return this.isTopRow(row) || this.isBottomRow(row);
   }
 
   /**
@@ -314,8 +354,8 @@ class TypesContainer {
    * @param row The row to check.
    * @returns 1 if the object stores information about an input row.
    */
-  isInputRow(row: Row): number {
-    return row.type & this.INPUT_ROW;
+  isInputRow(row: Row): row is InputRow {
+    return (row.type & this.INPUT_ROW) >= 1;
   }
 }
 

core/renderers/thrasos/info.ts

@@ -9,11 +9,8 @@
 import type {BlockSvg} from '../../block_svg.js';
 import {RenderInfo as BaseRenderInfo} from '../common/info.js';
 import type {Measurable} from '../measurables/base.js';
-import type {BottomRow} from '../measurables/bottom_row.js';
-import type {Field} from '../measurables/field.js';
 import {InRowSpacer} from '../measurables/in_row_spacer.js';
 import type {Row} from '../measurables/row.js';
-import type {TopRow} from '../measurables/top_row.js';
 import {Types} from '../measurables/types.js';
 import type {Renderer} from './renderer.js';
 
@@ -94,7 +91,7 @@ export class RenderInfo extends BaseRenderInfo {
   override getInRowSpacing_(prev: Measurable | null, next: Measurable | null) {
     if (!prev) {
       // Between an editable field and the beginning of the row.
-      if (next && Types.isField(next) && (next as Field).isEditable) {
+      if (next && Types.isField(next) && next.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       }
       // Inline input at the beginning of the row.
@@ -111,7 +108,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between a non-input and the end of the row.
     if (!Types.isInput(prev) && !next) {
       // Between an editable field and the end of the row.
-      if (Types.isField(prev) && (prev as Field).isEditable) {
+      if (Types.isField(prev) && prev.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       }
       // Padding at the end of an icon-only row to make the block shape clearer.
@@ -151,7 +148,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between a non-input and an input.
     if (!Types.isInput(prev) && next && Types.isInput(next)) {
       // Between an editable field and an input.
-      if (Types.isField(prev) && (prev as Field).isEditable) {
+      if (Types.isField(prev) && prev.isEditable) {
         if (Types.isInlineInput(next)) {
           return this.constants_.SMALL_PADDING;
         } else if (Types.isExternalInput(next)) {
@@ -177,7 +174,7 @@ export class RenderInfo extends BaseRenderInfo {
     // Spacing between an inline input and a field.
     if (Types.isInlineInput(prev) && next && Types.isField(next)) {
       // Editable field after inline input.
-      if ((next as Field).isEditable) {
+      if (next.isEditable) {
         return this.constants_.MEDIUM_PADDING;
       } else {
         // Noneditable field after inline input.
@@ -205,7 +202,7 @@ export class RenderInfo extends BaseRenderInfo {
       Types.isField(prev) &&
       next &&
       Types.isField(next) &&
-      (prev as Field).isEditable === (next as Field).isEditable
+      prev.isEditable === next.isEditable
     ) {
       return this.constants_.LARGE_PADDING;
     }
@@ -247,20 +244,17 @@ export class RenderInfo extends BaseRenderInfo {
       return row.yPos + elem.height / 2;
     }
     if (Types.isBottomRow(row)) {
-      const bottomRow = row as BottomRow;
-      const baseline =
-        bottomRow.yPos + bottomRow.height - bottomRow.descenderHeight;
+      const baseline = row.yPos + row.height - row.descenderHeight;
       if (Types.isNextConnection(elem)) {
         return baseline + elem.height / 2;
       }
       return baseline - elem.height / 2;
     }
     if (Types.isTopRow(row)) {
-      const topRow = row as TopRow;
       if (Types.isHat(elem)) {
-        return topRow.capline - elem.height / 2;
+        return row.capline - elem.height / 2;
       }
-      return topRow.capline + elem.height / 2;
+      return row.capline + elem.height / 2;
     }
 
     let result = row.yPos;

core/renderers/zelos/drawer.ts

@@ -15,7 +15,6 @@ import {Connection} from '../measurables/connection.js';
 import type {InlineInput} from '../measurables/inline_input.js';
 import {OutputConnection} from '../measurables/output_connection.js';
 import type {Row} from '../measurables/row.js';
-import type {SpacerRow} from '../measurables/spacer_row.js';
 import {Types} from '../measurables/types.js';
 import type {InsideCorners} from './constants.js';
 import type {RenderInfo} from './info.js';
@@ -96,20 +95,19 @@ export class Drawer extends BaseDrawer {
       return;
     }
     if (Types.isSpacer(row)) {
-      const spacerRow = row as SpacerRow;
-      const precedesStatement = spacerRow.precedesStatement;
-      const followsStatement = spacerRow.followsStatement;
+      const precedesStatement = row.precedesStatement;
+      const followsStatement = row.followsStatement;
       if (precedesStatement || followsStatement) {
         const insideCorners = this.constants_.INSIDE_CORNERS as InsideCorners;
         const cornerHeight = insideCorners.rightHeight;
         const remainingHeight =
-          spacerRow.height - (precedesStatement ? cornerHeight : 0);
+          row.height - (precedesStatement ? cornerHeight : 0);
         const bottomRightPath = followsStatement
           ? insideCorners.pathBottomRight
           : '';
         const verticalPath =
           remainingHeight > 0
-            ? svgPaths.lineOnAxis('V', spacerRow.yPos + remainingHeight)
+            ? svgPaths.lineOnAxis('V', row.yPos + remainingHeight)
             : '';
         const topRightPath = precedesStatement
           ? insideCorners.pathTopRight

core/renderers/zelos/info.ts

@@ -20,7 +20,6 @@ import {RenderInfo as BaseRenderInfo} from '../common/info.js';
 import type {Measurable} from '../measurables/base.js';
 import {Field} from '../measurables/field.js';
 import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {InputConnection} from '../measurables/input_connection.js';
 import type {Row} from '../measurables/row.js';
 import type {SpacerRow} from '../measurables/spacer_row.js';
 import {Types} from '../measurables/types.js';
@@ -207,9 +206,8 @@ export class RenderInfo extends BaseRenderInfo {
     }
     // Top and bottom rows act as a spacer so we don't need any extra padding.
     if (Types.isTopRow(prev)) {
-      const topRow = prev as TopRow;
       if (
-        !topRow.hasPreviousConnection &&
+        !prev.hasPreviousConnection &&
         (!this.outputConnection || this.hasStatementInput)
       ) {
         return Math.abs(
@@ -219,7 +217,6 @@ export class RenderInfo extends BaseRenderInfo {
       return this.constants_.NO_PADDING;
     }
     if (Types.isBottomRow(next)) {
-      const bottomRow = next as BottomRow;
       if (!this.outputConnection) {
         const topHeight =
           Math.max(
@@ -230,7 +227,7 @@ export class RenderInfo extends BaseRenderInfo {
             ),
           ) - this.constants_.CORNER_RADIUS;
         return topHeight;
-      } else if (!bottomRow.hasNextConnection && this.hasStatementInput) {
+      } else if (!next.hasNextConnection && this.hasStatementInput) {
         return Math.abs(
           this.constants_.NOTCH_HEIGHT - this.constants_.CORNER_RADIUS,
         );
@@ -259,7 +256,7 @@ export class RenderInfo extends BaseRenderInfo {
     ) {
       return row.yPos + this.constants_.EMPTY_STATEMENT_INPUT_HEIGHT / 2;
     }
-    if (Types.isInlineInput(elem) && elem instanceof InputConnection) {
+    if (Types.isInlineInput(elem)) {
       const connectedBlock = elem.connectedBlock;
       if (
         connectedBlock &&
@@ -308,7 +305,6 @@ export class RenderInfo extends BaseRenderInfo {
         }
         if (
           Types.isField(elem) &&
-          elem instanceof Field &&
           elem.parentInput === this.rightAlignedDummyInputs.get(row)
         ) {
           break;
@@ -371,7 +367,6 @@ export class RenderInfo extends BaseRenderInfo {
               xCursor < minXPos &&
               !(
                 Types.isField(elem) &&
-                elem instanceof Field &&
                 (elem.field instanceof FieldLabel ||
                   elem.field instanceof FieldImage)
               )
@@ -525,7 +520,7 @@ export class RenderInfo extends BaseRenderInfo {
           return 0;
       }
     }
-    if (Types.isInlineInput(elem) && elem instanceof InputConnection) {
+    if (Types.isInlineInput(elem)) {
       const connectedBlock = elem.connectedBlock;
       const innerShape = connectedBlock
         ? (connectedBlock.pathObject as PathObject).outputShapeType
@@ -552,7 +547,7 @@ export class RenderInfo extends BaseRenderInfo {
         connectionWidth -
         this.constants_.SHAPE_IN_SHAPE_PADDING[outerShape][innerShape]
       );
-    } else if (Types.isField(elem) && elem instanceof Field) {
+    } else if (Types.isField(elem)) {
       // Special case for text inputs.
       if (
         outerShape === constants.SHAPES.ROUND &&
@@ -616,7 +611,6 @@ export class RenderInfo extends BaseRenderInfo {
           for (let j = 0; j < row.elements.length; j++) {
             const elem = row.elements[j];
             if (
-              elem instanceof InputConnection &&
               Types.isInlineInput(elem) &&
               elem.connectedBlock &&
               !elem.connectedBlock.isShadow() &&