diff --git a/src/vs/editor/common/model/editableTextModel.ts b/src/vs/editor/common/model/editableTextModel.ts
index 2df8c63382883..44bcf28c268df 100644
--- a/src/vs/editor/common/model/editableTextModel.ts
+++ b/src/vs/editor/common/model/editableTextModel.ts
@@ -7,7 +7,7 @@
 import { Range, IRange } from 'vs/editor/common/core/range';
 import * as editorCommon from 'vs/editor/common/editorCommon';
 import { EditStack } from 'vs/editor/common/model/editStack';
-import { ILineEdit, LineMarker, ModelLine, MarkersTracker } from 'vs/editor/common/model/modelLine';
+import { ILineEdit, LineMarker, ModelLine, MarkersTracker, IModelLine } from 'vs/editor/common/model/modelLine';
 import { TextModelWithDecorations, ModelDecorationOptions } from 'vs/editor/common/model/textModelWithDecorations';
 import * as strings from 'vs/base/common/strings';
 import * as arrays from 'vs/base/common/arrays';
@@ -649,7 +649,7 @@ export class EditableTextModel extends TextModelWithDecorations implements edito
 				this._invalidateLine(spliceLineNumber - 1);
 
 				// Lines in the middle
-				let newLines: ModelLine[] = [];
+				let newLines: IModelLine[] = [];
 				let newLinesContent: string[] = [];
 				let newLinesLengths = new Uint32Array(insertingLinesCnt - editingLinesCnt);
 				for (let j = editingLinesCnt + 1; j <= insertingLinesCnt; j++) {
diff --git a/src/vs/editor/common/model/modelLine.ts b/src/vs/editor/common/model/modelLine.ts
index 50fd78c893098..dfe85c80b254a 100644
--- a/src/vs/editor/common/model/modelLine.ts
+++ b/src/vs/editor/common/model/modelLine.ts
@@ -158,7 +158,36 @@ function computePlusOneIndentLevel(line: string, tabSize: number): number {
 	return indent + 1;
 }
 
-export class ModelLine {
+export interface IModelLine {
+	readonly text: string;
+	isInvalid: boolean;
+
+	// --- markers
+	addMarker(marker: LineMarker): void;
+	addMarkers(markers: LineMarker[]): void;
+	removeMarker(marker: LineMarker): void;
+	removeMarkers(deleteMarkers: { [markerId: string]: boolean; }): void;
+	getMarkers(): LineMarker[];
+
+	// --- tokenization
+	resetTokenizationState(): void;
+	getState(): IState;
+	setState(state: IState): void;
+	getTokens(topLevelLanguageId: LanguageId): LineTokens;
+	setTokens(topLevelLanguageId: LanguageId, tokens: Uint32Array): void;
+
+	// --- indentation
+	updateTabSize(tabSize: number): void;
+	getIndentLevel(): number;
+
+	// --- editing
+	updateLineNumber(markersTracker: MarkersTracker, newLineNumber: number): void;
+	applyEdits(markersTracker: MarkersTracker, edits: ILineEdit[], tabSize: number): number;
+	append(markersTracker: MarkersTracker, myLineNumber: number, other: ModelLine, tabSize: number): void;
+	split(markersTracker: MarkersTracker, splitColumn: number, forceMoveMarkers: boolean, tabSize: number): ModelLine;
+}
+
+export class ModelLine implements IModelLine {
 
 	private _text: string;
 	public get text(): string { return this._text; }
diff --git a/src/vs/editor/common/model/textModel.ts b/src/vs/editor/common/model/textModel.ts
index 45b786fc2f959..2958d203e26e2 100644
--- a/src/vs/editor/common/model/textModel.ts
+++ b/src/vs/editor/common/model/textModel.ts
@@ -9,7 +9,7 @@ import * as strings from 'vs/base/common/strings';
 import { Position, IPosition } from 'vs/editor/common/core/position';
 import { Range, IRange } from 'vs/editor/common/core/range';
 import * as editorCommon from 'vs/editor/common/editorCommon';
-import { ModelLine } from 'vs/editor/common/model/modelLine';
+import { ModelLine, IModelLine } from 'vs/editor/common/model/modelLine';
 import { guessIndentation } from 'vs/editor/common/model/indentationGuesser';
 import { EDITOR_MODEL_DEFAULTS } from 'vs/editor/common/config/editorOptions';
 import { PrefixSumComputer } from 'vs/editor/common/viewModel/prefixSumComputer';
@@ -76,7 +76,7 @@ export class TextModel implements editorCommon.ITextModel {
 
 	protected readonly _eventEmitter: OrderGuaranteeEventEmitter;
 
-	/*protected*/ _lines: ModelLine[];
+	/*protected*/ _lines: IModelLine[];
 	protected _EOL: string;
 	protected _isDisposed: boolean;
 	protected _isDisposing: boolean;
@@ -756,7 +756,7 @@ export class TextModel implements editorCommon.ITextModel {
 	private _constructLines(textSource: ITextSource): void {
 		const tabSize = this._options.tabSize;
 		let rawLines = textSource.lines;
-		let modelLines: ModelLine[] = [];
+		let modelLines: IModelLine[] = [];
 
 		for (let i = 0, len = rawLines.length; i < len; i++) {
 			modelLines[i] = new ModelLine(rawLines[i], tabSize);