Default Interface Method Prototype (#10505)

* allow non-zero RVA on abstract interface method in ilasm

* Revert "allow non-zero RVA on abstract interface method in ilasm"

This reverts commit eecb8024e58f14a20e5e49359f38019f5768ac41.

* add a test case and allow virtual non-abstract method in ilasm

* allow non-abstract methods in the loader

* fixup dispatch map

* support for simple default interface method scenario

* fix a bug with incorrect usage of MethodIterator skpping the first method. add a test case for overriding but it may not be what we want

* add another simple test case for base class

* allow private/internal methods in ilasm and add a explict impl test

* update reference to mscorlib in il test

* add shared generics and variance case

* allow interface dispatch to return instantiating stubs with the right PARAM_TYPE calling conv

* simple factoring and add a valuetype test case

* add a test case for generic virtual methods

* a bit more refactoring by moving the CALLCONV_PARAMTYPE logic inside getMethodSigInternal

* support explicit methodimpl and remove implicit methodimpl test case

* update test cases to give more clear output

* Fix a bug where GetMethodDescForSlot chokes on interface MethodDesc without precode. This is accdentally discovered by methodimpl test case when iterating methods on a default interface method that has already been JITted

* cleanup code after review and add a bit more comments

* update comments

* only use custom ILAsm for default interface methods tests - some tests are choking on CoreCLR ilasm for security related stuff

* address comments and allow instance methods, and add a constraint value type call test scenario

* disable the failing protected method scenario

1 files changed, 13 insertions, 5 deletions

diff --git a/src/vm/method.cpp b/src/vm/method.cpp
index 241a0ccee0..5ac5cafd01 100644
--- a/src/vm/method.cpp
+++ b/src/vm/method.cpp
@@ -1762,7 +1762,11 @@ BOOL MethodDesc::IsSharedByGenericMethodInstantiations()
 // Does this method require an extra MethodTable argument for instantiation information?
 // This is the case for
 // * per-inst static methods in shared-code instantiated generic classes (e.g. static void MyClass<string>::m())
+//     - there is no this pointer providing generic dictionary info
 // * shared-code instance methods in instantiated generic structs (e.g. void MyValueType<string>::m())
+//     - unboxed 'this' pointer in value-type instance methods don't have MethodTable pointer by definition
+// * default interface method called via interface dispatch (e. g. IFoo<string>.Foo calling into IFoo<object>::Foo())
+//     - this pointer is ambiguous as it can implement more than one IFoo<T>
 BOOL MethodDesc::RequiresInstMethodTableArg() 
 {
     LIMITED_METHOD_DAC_CONTRACT;
@@ -1770,7 +1774,7 @@ BOOL MethodDesc::RequiresInstMethodTableArg()
     return
         IsSharedByGenericInstantiations() &&
         !HasMethodInstantiation() &&
-        (IsStatic() || GetMethodTable()->IsValueType());
+        (IsStatic() || GetMethodTable()->IsValueType() || IsDefaultInterfaceMethod());
 }
 
 //*******************************************************************************
@@ -1792,7 +1796,7 @@ BOOL MethodDesc::RequiresInstArg()
     LIMITED_METHOD_DAC_CONTRACT;
 
     BOOL fRet = IsSharedByGenericInstantiations() &&
-        (HasMethodInstantiation() || IsStatic() || GetMethodTable()->IsValueType());
+        (HasMethodInstantiation() || IsStatic() || GetMethodTable()->IsValueType() || IsDefaultInterfaceMethod());
 
     _ASSERT(fRet == (RequiresInstMethodTableArg() || RequiresInstMethodDescArg()));
     return fRet;
@@ -1868,7 +1872,8 @@ BOOL MethodDesc::AcquiresInstMethodTableFromThis() {
         IsSharedByGenericInstantiations()  &&
         !HasMethodInstantiation() &&
         !IsStatic() &&
-        !GetMethodTable()->IsValueType();
+        !GetMethodTable()->IsValueType() &&
+        !IsDefaultInterfaceMethod();
 }
 
 //*******************************************************************************
@@ -2582,7 +2587,10 @@ BOOL MethodDesc::RequiresStableEntryPoint(BOOL fEstimateForChunk /*=FALSE*/)
             return TRUE;
 
         // TODO: Can we avoid early allocation of precodes for interfaces and cominterop?
-        if ((IsInterface() && !IsStatic()) || IsComPlusCall())
+        // Only abstract virtual interface method need precode
+        // @DIM_TODO - We need to decide what is the right approach for precode for default 
+        // interface methods
+        if ((IsInterface() && IsAbstract() && IsVirtual() && !IsStatic()) || IsComPlusCall())
             return TRUE;
     }
 
@@ -2678,7 +2686,7 @@ BOOL MethodDesc::MayHaveNativeCode()
 
     _ASSERTE(IsIL());
 
-    if ((IsInterface() && !IsStatic()) || IsWrapperStub() || ContainsGenericVariables() || IsAbstract())
+    if (IsWrapperStub() || ContainsGenericVariables() || IsAbstract())
     {
         return FALSE;
     }