Fix compiling methods with explicit this (#103045)

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

Author: MichalStrehovsky

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;
         }