[FIR] KT-59368 context receiver subtyping checker

compiler/fir/analysis-tests/testData/resolve/checkers/contextReceiversSubtyping.fir.txt

@@ -0,0 +1,27 @@
+FILE: contextReceiversSubtyping.kt
+    public abstract interface D : R|D1|, R|D2| {
+    }
+    public abstract interface D1 : R|kotlin/Any| {
+    }
+    public abstract interface D2 : R|kotlin/Any| {
+    }
+    context(R|T|, R|D2|)
+    public final fun <T : R|D1|, R|D2|> foo(): R|kotlin/Unit| {
+    }
+    public abstract interface Cov<out T> : R|kotlin/Any| {
+    }
+    public final class A : R|kotlin/Any| {
+        public constructor(): R|A| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final class B : R|kotlin/Any| {
+        public constructor(): R|B| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    context(R|Cov<T>|, R|Cov<B>|)
+    public final fun <T : R|A|> foo(): R|kotlin/Unit| {
+    }

compiler/fir/analysis-tests/testData/resolve/checkers/contextReceiversSubtyping.kt

@@ -0,0 +1,19 @@
+// FIR_IDENTICAL
+// !LANGUAGE: +ContextReceivers
+
+interface D: D1, D2 {}
+interface D1 {}
+interface D2 {}
+
+<!SUBTYPING_BETWEEN_CONTEXT_RECEIVERS!>context(T, D2)<!>
+fun <T> foo() where T: D1, T: D2 {}
+
+interface Cov<out T> {}
+class A {}
+class B {}
+
+// This sholdn't be an error since the type parameter is predetermined to be `A`,
+// which causes that there can't be subtyping between the context receivers.
+// However, the cheking is simplified because it is time-consuming process.
+<!SUBTYPING_BETWEEN_CONTEXT_RECEIVERS!>context(Cov<T>, Cov<B>)<!>
+fun <T: <!FINAL_UPPER_BOUND!>A<!>> foo() {}