Merge from vscode 1a81711a85e38ccf784110568ebf3784ab9094a5 (#9161)

* Merge from vscode 1a81711a85e38ccf784110568ebf3784ab9094a5

* small spacing fix

src/vs/editor/common/modes.ts

@@ -265,6 +265,34 @@ export interface HoverProvider {
 	provideHover(model: model.ITextModel, position: Position, token: CancellationToken): ProviderResult<Hover>;
 }
 
+/**
+ * An evaluatable expression represents additional information for an expression in a document. Evaluatable expression are
+ * evaluated by a debugger or runtime and their result is rendered in a tooltip-like widget.
+ */
+export interface EvaluatableExpression {
+	/**
+	 * The range to which this expression applies.
+	 */
+	range: IRange;
+	/*
+	 * This expression overrides the expression extracted from the range.
+	 */
+	expression?: string;
+}
+
+/**
+ * The hover provider interface defines the contract between extensions and
+ * the [hover](https://code.visualstudio.com/docs/editor/intellisense)-feature.
+ */
+export interface EvaluatableExpressionProvider {
+	/**
+	 * Provide a hover for the given position and document. Multiple hovers at the same
+	 * position will be merged by the editor. A hover can have a range which defaults
+	 * to the word range at the position when omitted.
+	 */
+	provideEvaluatableExpression(model: model.ITextModel, position: Position, token: CancellationToken): ProviderResult<EvaluatableExpression>;
+}
+
 export const enum CompletionItemKind {
 	Method,
 	Function,
@@ -1595,6 +1623,11 @@ export const SignatureHelpProviderRegistry = new LanguageFeatureRegistry<Signatu
  */
 export const HoverProviderRegistry = new LanguageFeatureRegistry<HoverProvider>();
 
+/**
+ * @internal
+ */
+export const EvaluatableExpressionProviderRegistry = new LanguageFeatureRegistry<EvaluatableExpressionProvider>();
+
 /**
  * @internal
  */