Fix compiling methods with explicit this (#103045)

One of the pri1 JIT tests hits asserts because we forget to set the bit.

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -883,6 +883,7 @@ private void Get_CORINFO_SIG_INFO(MethodSignature signature, CORINFO_SIG_INFO* s
  ThrowHelper.ThrowBadImageFormatException();
 
  if (!signature.IsStatic) sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_HASTHIS;
+ if (signature.IsExplicitThis) sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_EXPLICITTHIS;
 
  TypeDesc returnType = signature.ReturnType;
 

src/coreclr/tools/Common/TypeSystem/Common/MethodDesc.cs

@@ -22,6 +22,7 @@ public enum MethodSignatureFlags
  UnmanagedCallingConvention = 0x0009,
 
  Static = 0x0010,
+ ExplicitThis = 0x0020,
  }
 
  public enum EmbeddedSignatureDataKind
@@ -129,6 +130,14 @@ public bool IsStatic
  }
  }
 
+ public bool IsExplicitThis
+ {
+ get
+ {
+ return (_flags & MethodSignatureFlags.ExplicitThis) != 0;
+ }
+ }
+
  public int GenericParameterCount
  {
  get

src/coreclr/tools/Common/TypeSystem/Ecma/EcmaSignatureParser.cs

@@ -380,6 +380,9 @@ private MethodSignature ParseMethodSignatureImpl(bool skipEmbeddedSignatureData)
  if (!header.IsInstance)
  flags |= MethodSignatureFlags.Static;
 
+ if (header.HasExplicitThis)
+ flags |= MethodSignatureFlags.ExplicitThis;
+
  int arity = header.IsGeneric ? _reader.ReadCompressedInteger() : 0;
 
  int count = _reader.ReadCompressedInteger();

src/coreclr/tools/Common/TypeSystem/MetadataEmitter/TypeSystemMetadataEmitter.cs

@@ -658,9 +658,9 @@ public void Pop()
  private void EncodeMethodSignature(BlobBuilder signatureBuilder, MethodSignature sig, EmbeddedSignatureDataEmitter signatureDataEmitter)
  {
  signatureDataEmitter.Push();
- BlobEncoder signatureEncoder = new BlobEncoder(signatureBuilder);
  int genericParameterCount = sig.GenericParameterCount;
  bool isInstanceMethod = !sig.IsStatic;
+ bool isExplicitThis = sig.IsExplicitThis;
  SignatureCallingConvention sigCallingConvention = SignatureCallingConvention.Default;
  switch (sig.Flags & MethodSignatureFlags.UnmanagedCallingConventionMask)
  {
@@ -685,7 +685,15 @@ private void EncodeMethodSignature(BlobBuilder signatureBuilder, MethodSignature
  if (sigCallingConvention != SignatureCallingConvention.Default)
  signatureDataEmitter.UpdateSignatureCallingConventionAtCurrentIndexStack(ref sigCallingConvention);
 
- signatureEncoder.MethodSignature(sigCallingConvention, genericParameterCount, isInstanceMethod);
+ SignatureAttributes attributes =
+ (genericParameterCount != 0 ? SignatureAttributes.Generic : 0) |
+ (isInstanceMethod ? SignatureAttributes.Instance : 0) |
+ (isExplicitThis ? SignatureAttributes.ExplicitThis : 0);
+
+ signatureBuilder.WriteByte(new SignatureHeader(SignatureKind.Method, sigCallingConvention, attributes).RawValue);
+ if (genericParameterCount != 0)
+ signatureBuilder.WriteCompressedInteger(genericParameterCount);
+
  signatureBuilder.WriteCompressedInteger(sig.Length);
  EncodeType(signatureBuilder, sig.ReturnType, signatureDataEmitter);
  for (int i = 0; i < sig.Length; i++)

src/coreclr/tools/aot/ILCompiler.MetadataTransform/ILCompiler/Metadata/Transform.Method.cs

@@ -241,6 +241,10 @@ private static SignatureCallingConvention GetSignatureCallingConvention(Cts.Meth
  {
  callingConvention |= SignatureCallingConvention.HasThis;
  }
+ if ((signature.Flags & Cts.MethodSignatureFlags.ExplicitThis) != 0)
+ {
+ callingConvention |= SignatureCallingConvention.ExplicitThis;
+ }
  return callingConvention;
  }