Fixes https://github.com/microsoft/monaco-editor/issues/3920

src/vs/editor/browser/view/viewLayer.ts

@@ -8,6 +8,7 @@ import { StringBuilder } from 'vs/editor/common/core/stringBuilder';
 import * as viewEvents from 'vs/editor/common/viewEvents';
 import { ViewportData } from 'vs/editor/common/viewLayout/viewLinesViewportData';
 import { EditorOption } from 'vs/editor/common/config/editorOptions';
+import { BugIndicatingError } from 'vs/base/common/errors';
 
 /**
  * Represents a visible line
@@ -80,7 +81,7 @@ export class RenderedLinesCollection<T extends ILine> {
 	public getLine(lineNumber: number): T {
 		const lineIndex = lineNumber - this._rendLineNumberStart;
 		if (lineIndex < 0 || lineIndex >= this._lines.length) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 		return this._lines[lineIndex];
 	}

src/vs/editor/common/model/guidesTextModelPart.ts

@@ -13,6 +13,7 @@ import { TextModelPart } from 'vs/editor/common/model/textModelPart';
 import { computeIndentLevel } from 'vs/editor/common/model/utils';
 import { ILanguageConfigurationService, ResolvedLanguageConfiguration } from 'vs/editor/common/languages/languageConfigurationRegistry';
 import { BracketGuideOptions, HorizontalGuidesState, IActiveIndentGuideInfo, IGuidesTextModelPart, IndentGuide, IndentGuideHorizontalLine } from 'vs/editor/common/textModelGuides';
+import { BugIndicatingError } from 'vs/base/common/errors';
 
 export class GuidesTextModelPart extends TextModelPart implements IGuidesTextModelPart {
 	constructor(
@@ -46,7 +47,7 @@ export class GuidesTextModelPart extends TextModelPart implements IGuidesTextMod
 		const lineCount = this.textModel.getLineCount();
 
 		if (lineNumber < 1 || lineNumber > lineCount) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 
 		const foldingRules = this.getLanguageConfiguration(

src/vs/editor/common/model/textModel.ts

@@ -6,7 +6,7 @@
 import { ArrayQueue, pushMany } from 'vs/base/common/arrays';
 import { VSBuffer, VSBufferReadableStream } from 'vs/base/common/buffer';
 import { Color } from 'vs/base/common/color';
-import { illegalArgument, onUnexpectedError } from 'vs/base/common/errors';
+import { BugIndicatingError, illegalArgument, onUnexpectedError } from 'vs/base/common/errors';
 import { Emitter, Event } from 'vs/base/common/event';
 import { IMarkdownString } from 'vs/base/common/htmlContent';
 import { combinedDisposable, Disposable, IDisposable, MutableDisposable } from 'vs/base/common/lifecycle';
@@ -792,7 +792,7 @@ export class TextModel extends Disposable implements model.ITextModel, IDecorati
 	public getLineContent(lineNumber: number): string {
 		this._assertNotDisposed();
 		if (lineNumber < 1 || lineNumber > this.getLineCount()) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 
 		return this._buffer.getLineContent(lineNumber);
@@ -801,7 +801,7 @@ export class TextModel extends Disposable implements model.ITextModel, IDecorati
 	public getLineLength(lineNumber: number): number {
 		this._assertNotDisposed();
 		if (lineNumber < 1 || lineNumber > this.getLineCount()) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 
 		return this._buffer.getLineLength(lineNumber);
@@ -834,23 +834,23 @@ export class TextModel extends Disposable implements model.ITextModel, IDecorati
 	public getLineMaxColumn(lineNumber: number): number {
 		this._assertNotDisposed();
 		if (lineNumber < 1 || lineNumber > this.getLineCount()) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 		return this._buffer.getLineLength(lineNumber) + 1;
 	}
 
 	public getLineFirstNonWhitespaceColumn(lineNumber: number): number {
 		this._assertNotDisposed();
 		if (lineNumber < 1 || lineNumber > this.getLineCount()) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 		return this._buffer.getLineFirstNonWhitespaceColumn(lineNumber);
 	}
 
 	public getLineLastNonWhitespaceColumn(lineNumber: number): number {
 		this._assertNotDisposed();
 		if (lineNumber < 1 || lineNumber > this.getLineCount()) {
-			throw new Error('Illegal value for lineNumber');
+			throw new BugIndicatingError('Illegal value for lineNumber');
 		}
 		return this._buffer.getLineLastNonWhitespaceColumn(lineNumber);
 	}

src/vs/editor/common/model/tokenizationTextModelPart.ts

@@ -544,7 +544,7 @@ class GrammarTokens extends Disposable {
 			return;
 		}
 
-		startLineNumber = Math.max(1, startLineNumber);
+		startLineNumber = Math.max(1, Math.min(this._textModel.getLineCount(), startLineNumber));
 		endLineNumber = Math.min(this._textModel.getLineCount(), endLineNumber);
 
 		const builder = new ContiguousMultilineTokensBuilder();