mapped type indent

Author: Arthur Ozga

src/compiler/checker.ts

@@ -2516,7 +2516,8 @@ namespace ts {
                     const readonlyToken = type.declaration && type.declaration.readonlyToken ? createToken(SyntaxKind.ReadonlyKeyword) : undefined;
                     const questionToken = type.declaration && type.declaration.questionToken ? createToken(SyntaxKind.QuestionToken) : undefined;
 
-                    return createMappedTypeNode(readonlyToken, typeParameterNode, questionToken, templateTypeNode);
+                    const mappedTypeNode = createMappedTypeNode(readonlyToken, typeParameterNode, questionToken, templateTypeNode);
+                    return setEmitFlags(mappedTypeNode, EmitFlags.SingleLine);
                 }
 
                 function createAnonymousTypeNode(type: ObjectType): TypeNode {

src/compiler/emitter.ts

@@ -1004,9 +1004,15 @@ namespace ts {
         }
 
         function emitMappedType(node: MappedTypeNode) {
+            const emitFlags = getEmitFlags(node);
             write("{");
-            writeLine();
-            increaseIndent();
+            if (emitFlags & EmitFlags.SingleLine) {
+                write(" ");
+            }
+            else {
+                writeLine();
+                increaseIndent();
+            }
             writeIfPresent(node.readonlyToken, "readonly ");
             write("[");
             emit(node.typeParameter.name);
@@ -1017,8 +1023,13 @@ namespace ts {
             write(": ");
             emit(node.type);
             write(";");
-            writeLine();
-            decreaseIndent();
+            if (emitFlags & EmitFlags.SingleLine) {
+                write(" ");
+            }
+            else {
+                writeLine();
+                decreaseIndent();
+            }
             write("}");
         }