Adding Expression.type (#6327)

Author: greg-at-moderne

rewrite-javascript/rewrite/src/java/tree.ts

@@ -37,6 +37,7 @@ export namespace J {
 }
 
 export interface Expression extends J {
+    readonly type?: Type;
 }
 
 export interface MethodCall extends Expression {

rewrite-javascript/rewrite/test/javascript/parser/binary.test.ts

@@ -27,7 +27,7 @@ describe('arithmetic operator mapping', () => {
                 '1 + 2'
             ),
             afterRecipe: (cu: JS.CompilationUnit) => {
-                const binary = (cu.statements[0].element as JS.ExpressionStatement).expression as J.Binary;
+                const binary = (cu.statements[0].element as JS.ExpressionStatement).expression;
                 expect(binary.type).toBe(Type.Primitive.Double);
             }
         }));
@@ -39,7 +39,7 @@ describe('arithmetic operator mapping', () => {
                 '"1" + 2'
             ),
             afterRecipe: (cu: JS.CompilationUnit) => {
-                const binary = (cu.statements[0].element as JS.ExpressionStatement).expression as J.Binary;
+                const binary = (cu.statements[0].element as JS.ExpressionStatement).expression;
                 expect(binary.type).toBe(Type.Primitive.String);
             }
         }));