WIP - don't provide a breaking change

Author: orta

src/services/classifier2020.ts

@@ -18,12 +18,12 @@ namespace ts.classifier.v2020 {
     }
 
     /** This is mainly used internally for testing */
-    export function getSemanticClassifications(program: Program, cancellationToken: CancellationToken, sourceFile: SourceFile, span: TextSpan): ClassifiedSpan[] {
+    export function getSemanticClassifications(program: Program, cancellationToken: CancellationToken, sourceFile: SourceFile, span: TextSpan): ClassifiedSpan2020[] {
         const classifications = getEncodedSemanticClassifications(program, cancellationToken, sourceFile, span);
 
         Debug.assert(classifications.spans.length % 3 === 0);
         const dense = classifications.spans;
-        const result: ClassifiedSpan[] = [];
+        const result: ClassifiedSpan2020[] = [];
         for (let i = 0; i < dense.length; i += 3) {
             result.push({
                 textSpan: createTextSpan(dense[i], dense[i + 1]),

src/services/services.ts

@@ -1797,7 +1797,7 @@ namespace ts {
             return kind === ScriptKind.TS || kind === ScriptKind.TSX;
         }
 
-        function getSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[] {
+        function getSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): (ClassifiedSpan| ClassifiedSpan2020)[] {
             if (!isTsOrTsxFile(fileName)) {
                 // do not run semantic classification on non-ts-or-tsx files
                 return [];
@@ -1829,7 +1829,7 @@ namespace ts {
             }
         }
 
-        function getSyntacticClassifications(fileName: string, span: TextSpan): ClassifiedSpan[] {
+        function getSyntacticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[] | ClassifiedSpan2020[] {
             // doesn't use compiler - no need to synchronize with host
             return ts.getSyntacticClassifications(cancellationToken, syntaxTreeCache.getCurrentSourceFile(fileName), span);
         }

src/services/types.ts

@@ -380,10 +380,15 @@ namespace ts {
         getCompilerOptionsDiagnostics(): Diagnostic[];
 
         /** @deprecated Use getEncodedSyntacticClassifications instead. */
-        getSyntacticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[];
+        getSyntacticClassifications(fileName: string, span: TextSpan, format: SemanticClassificationFormat.TwentyTwenty): ClassifiedSpan2020[];
+        getSyntacticClassifications(fileName: string, span: TextSpan, format: SemanticClassificationFormat.Original): ClassifiedSpan[];
+        getSyntacticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[] | ClassifiedSpan2020[];
 
         /** @deprecated Use getEncodedSemanticClassifications instead. */
-        getSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[];
+        getSemanticClassifications(fileName: string, span: TextSpan, format: SemanticClassificationFormat.TwentyTwenty): ClassifiedSpan2020[];
+        getSemanticClassifications(fileName: string, span: TextSpan, format: SemanticClassificationFormat.Original): ClassifiedSpan[];
+        getSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[] | ClassifiedSpan2020[];
+
         /** Encoded as triples of [start, length, ClassificationType]. */
         getEncodedSyntacticClassifications(fileName: string, span: TextSpan): Classifications;
 
@@ -603,7 +608,12 @@ namespace ts {
 
     export interface ClassifiedSpan {
         textSpan: TextSpan;
-        classificationType: ClassificationTypeNames | number;
+        classificationType: ClassificationTypeNames;
+    }
+
+    export interface ClassifiedSpan2020 {
+        textSpan: TextSpan;
+        classificationType: number;
     }
 
     /**