feat(lint): rule useExplicitReturnType (#9429)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: ematipico

.changeset/calm-impalas-stare.md

@@ -0,0 +1,12 @@
+---
+"@biomejs/biome": patch
+---
+
+Added the new nursery lint rule [`useExplicitReturnType`](https://biomejs.dev/linter/rules/use-explicit-return-type). It reports TypeScript functions and methods that omit an explicit return type.
+
+```ts
+function toString(x: any) { // rule triggered, it doesn't declare a return type
+  return x.toString()
+}
+```
+

crates/biome_configuration/src/analyzer/linter/rules.rs

@@ -1,9 +1,7 @@
 use crate::services::semantic::Semantic;
 use biome_analyze::{Rule, RuleDiagnostic, RuleSource, context::RuleContext, declare_lint_rule};
 use biome_console::markup;
-use biome_js_syntax::{
-    AnyFunctionLike, AnyJsFunction, JsCallExpression, JsParenthesizedExpression,
-};
+use biome_js_syntax::AnyFunctionLike;
 use biome_rowan::AstNode;
 use biome_rule_options::no_excessive_lines_per_function::NoExcessiveLinesPerFunctionOptions;
 
@@ -142,7 +140,7 @@ impl Rule for NoExcessiveLinesPerFunction {
         let options = ctx.options();
 
         if let AnyFunctionLike::AnyJsFunction(func) = binding
-            && is_iife(func)
+            && func.is_iife()
             && options.skip_iifes()
         {
             return None;
@@ -203,12 +201,6 @@ impl Rule for NoExcessiveLinesPerFunction {
     }
 }
 
-fn is_iife(func: &AnyJsFunction) -> bool {
-    func.parent::<JsParenthesizedExpression>()
-        .and_then(|expr| expr.parent::<JsCallExpression>())
-        .is_some()
-}
-
 pub struct State {
     function_lines_count: usize,
 }