Add the ability to add type annotations

Author: croutonn

lib/rules/func-style.js

@@ -92,6 +92,10 @@ module.exports = {
                 result.typeParameters = node.init.typeParameters && node.init.typeParameters.params && node.init.typeParameters.params.length ? node.init.typeParameters.params.map(t => sourceCode.getText(t)).join(", ") : null;
             }
 
+            if (result.typeAnnotation && !result.returnType) {
+                result.returnType = `ReturnType<${result.typeAnnotation}>`;
+            }
+
             return result;
         }
 
@@ -106,9 +110,9 @@ module.exports = {
                 case "declaration":
                     return `${data.async ? "async " : ""}function${data.name ? ` ${data.name}` : ""}${data.typeParameters ? `<${data.typeParameters}>` : ""}(${data.params ? data.params : ""})${data.returnType ? `: ${data.returnType}` : ""}`;
                 case "expression":
-                    return `${data.kind} ${data.name} = ${data.async ? "async " : ""}function${data.typeParameters ? `<${data.typeParameters}>` : ""}(${data.params ? data.params : ""})${data.returnType ? `: ${data.returnType}` : ""}`;
+                    return `${data.kind} ${data.name}${data.typeAnnotation ? `: ${data.typeAnnotation}` : ""} = ${data.async ? "async " : ""}function${data.typeParameters ? `<${data.typeParameters}>` : ""}(${data.params ? data.params : ""})${data.returnType ? `: ${data.returnType}` : ""}`;
                 case "arrow":
-                    return `${data.kind} ${data.name} = ${data.async ? "async " : ""}${data.typeParameters ? `<${data.typeParameters}>` : ""}(${data.params ? data.params : ""})${data.returnType ? `: ${data.returnType}` : ""} =>`;
+                    return `${data.kind} ${data.name}${data.typeAnnotation ? `: ${data.typeAnnotation}` : ""} = ${data.async ? "async " : ""}${data.typeParameters ? `<${data.typeParameters}>` : ""}(${data.params ? data.params : ""})${data.returnType ? `: ${data.returnType}` : ""} =>`;
                 default:
                     return null;
             }