ANN: Annotate Const Generics Defaults as experimental

Author: mchernyavsky

src/main/kotlin/org/rust/ide/annotator/RsErrorAnnotator.kt

@@ -1340,6 +1340,11 @@ private fun checkDuplicates(
 }
 
 private fun checkConstGenerics(holder: RsAnnotationHolder, constParameter: RsConstParameter) {
+    val default = constParameter.blockExpr
+    if (default != null) {
+        CONST_GENERICS_DEFAULTS.check(holder, default, "const generics defaults")
+    }
+
     val constGenericAvailability = CONST_GENERICS.availability(constParameter)
     if (constGenericAvailability == AVAILABLE) return
 

src/test/kotlin/org/rust/ide/annotator/RsErrorAnnotatorTest.kt

@@ -2913,6 +2913,23 @@ class RsErrorAnnotatorTest : RsAnnotatorTestBase(RsErrorAnnotator::class) {
         enum E<const C: i32> {}
     """)
 
+    @MockRustcVersion("1.51.0")
+    fun `test const generics defaults E0658 1`() = checkErrors("""
+        fn f<const C: i32 = <error descr="const generics defaults is experimental [E0658]">{ 0 }</error>>() {}
+        struct S<const C: i32 = <error descr="const generics defaults is experimental [E0658]">{ 0 }</error>>(A);
+        trait T<const C: i32 = <error descr="const generics defaults is experimental [E0658]">{ 0 }</error>> {}
+        enum E<const C: i32 = <error descr="const generics defaults is experimental [E0658]">{ 0 }</error>> {}
+    """)
+
+    @MockRustcVersion("1.51.0-nightly")
+    fun `test const generics defaults E0658 2`() = checkErrors("""
+        #![feature(const_generics_defaults)]
+        fn f<const C: i32 = { 0 }>() {}
+        struct S<const C: i32 = { 0 }>(A);
+        trait T<const C: i32 = { 0 }> {}
+        enum E<const C: i32 = { 0 }> {}
+    """)
+
     @MockRustcVersion("1.47.0")
     fun `test min const generics E0658 1`() = checkErrors("""
         fn f<<error descr="const generics is experimental [E0658]">const C: i32</error>>() {}