Allow Exit subtype to be a floating Effect

.changeset/metal-buses-rescue.md

@@ -0,0 +1,5 @@
+---
+"@effect/language-service": patch
+---
+
+Allow Exit subtype to be a floating Effect

examples/diagnostics/floatingEffect.ts

@@ -18,5 +18,10 @@ Effect.runPromise(Effect.gen(function*(){
 
 export function constructorFunction(this: { boot: Effect.Effect<void>}){
     this.boot = Effect.void
+    // ^- This is fine, its another way to perform an assignment
 }
 
+const main = Effect.gen(function*(){
+    yield* Effect.exit(Effect.void)
+    // ^- This is fine, returns an exit
+})

src/diagnostics/floatingEffect.ts

@@ -1,3 +1,4 @@
+import { pipe } from "effect/Function"
 import * as Option from "effect/Option"
 import ts from "typescript"
 import type { ApplicableDiagnosticDefinition } from "../definition.js"
@@ -31,8 +32,11 @@ export const floatingEffect = createDiagnostic({
         const effect = TypeParser.effectType(ts, typeChecker)(type, node.expression)
         if (Option.isSome(effect)) {
           // and not a fiber (we consider that a valid operation)
-          const fiber = TypeParser.fiberType(ts, typeChecker)(type, node.expression)
-          if (Option.isNone(fiber)) {
+          const allowedFloatingEffects = pipe(
+            TypeParser.fiberType(ts, typeChecker)(type, node.expression),
+            Option.orElse(() => TypeParser.effectSubtype(ts, typeChecker)(type, node.expression))
+          )
+          if (Option.isNone(allowedFloatingEffects)) {
             effectDiagnostics.push({
               node,
               category: ts.DiagnosticCategory.Error,

src/utils/TypeParser.ts

@@ -84,6 +84,21 @@ export function fiberType(ts: TypeScriptApi, typeChecker: ts.TypeChecker) {
     })
 }
 
+export function effectSubtype(ts: TypeScriptApi, typeChecker: ts.TypeChecker) {
+  return (type: ts.Type, atLocation: ts.Node) =>
+    Option.gen(function*(_) {
+      // there is no better way to check if a type is a subtype of effect
+      // so we just check for the existence of the property "_tag"
+      // which is common for Option, Either, and others
+      const tagSymbol = yield* Option.fromNullable(
+        typeChecker.getPropertyOfType(type, "_tag")
+      )
+      if (!tagSymbol) return yield* Option.none()
+      // and it is also an effect itself
+      return effectType(ts, typeChecker)(type, atLocation)
+    })
+}
+
 export function importedEffectModule(ts: TypeScriptApi, typeChecker: ts.TypeChecker) {
   return (node: ts.Node) =>
     Option.gen(function*() {