Report error when suspend call is illegal in the scope

Namely when it's not contained inside coroutine or another suspend function

 #KT-14924 In Progress

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -862,6 +862,7 @@ public interface Errors {
 
 
     DiagnosticFactory0<PsiElement> NON_LOCAL_SUSPENSION_POINT = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<PsiElement> ILLEGAL_SUSPEND_FUNCTION_CALL = DiagnosticFactory0.create(ERROR);
 
 
     // Error sets

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -820,6 +820,7 @@ public class DefaultErrorMessages {
         MAP.put(INLINE_CALL_CYCLE, "The ''{0}'' invocation is a part of inline cycle", NAME);
         MAP.put(NON_LOCAL_RETURN_IN_DISABLED_INLINE, "Non-local returns are not allowed with inlining disabled");
         MAP.put(NON_LOCAL_SUSPENSION_POINT, "Suspension functions can be called only within coroutine body");
+        MAP.put(ILLEGAL_SUSPEND_FUNCTION_CALL, "Suspend functions are only allowed to be called from a coroutine or another suspend function");
 
         MAP.setImmutable();
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/coroutineCallChecker.kt

@@ -47,11 +47,11 @@ object CoroutineSuspendCallChecker : CallChecker {
 
         when {
             enclosingSuspendFunction != null -> {
-                // TODO: check if tail call
+                // Tail calls checks happen during control flow analysis
+                // Here we only record enclosing function mapping (for backends purposes)
                 context.trace.record(BindingContext.ENCLOSING_SUSPEND_FUNCTION_FOR_SUSPEND_FUNCTION_CALL, resolvedCall.call, enclosingSuspendFunction)
             }
             closestCoroutineReceiver != null -> {
-
                 val callElement = resolvedCall.call.callElement as KtExpression
 
                 if (!InlineUtil.checkNonLocalReturnUsage(closestCoroutineReceiver.declarationDescriptor, callElement, context.resolutionContext)) {
@@ -60,6 +60,9 @@ object CoroutineSuspendCallChecker : CallChecker {
 
                 context.trace.record(BindingContext.COROUTINE_RECEIVER_FOR_SUSPENSION_POINT, resolvedCall.call, closestCoroutineReceiver)
             }
+            else -> {
+                context.trace.report(Errors.ILLEGAL_SUSPEND_FUNCTION_CALL.on(reportOn))
+            }
         }
     }
 }