[Serialization] Serialize type of default expression

This type is going to be use to infer generic parameters at the
call site.

Author: xedin

lib/Serialization/Deserialization.cpp

@@ -3197,13 +3197,15 @@ class DeclDeserializer {
     bool isIsolated;
     bool isCompileTimeConst;
     uint8_t rawDefaultArg;
+    TypeID defaultExprType;
 
     decls_block::ParamLayout::readRecord(scratch, argNameID, paramNameID,
                                          contextID, rawSpecifier,
                                          interfaceTypeID, isIUO, isVariadic,
                                          isAutoClosure, isIsolated,
                                          isCompileTimeConst,
-                                         rawDefaultArg);
+                                         rawDefaultArg,
+                                         defaultExprType);
 
     auto argName = MF.getIdentifier(argNameID);
     auto paramName = MF.getIdentifier(paramNameID);
@@ -3246,6 +3248,7 @@ class DeclDeserializer {
       param->setDefaultArgumentKind(*defaultArg);
       if (!blobData.empty())
         param->setDefaultValueStringRepresentation(blobData);
+      // TODO: Set default expression type.
     }
     return param;
   }

lib/Serialization/ModuleFormat.h

@@ -56,7 +56,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 671; // ParameterizedProtocolType with multiple arguments
+const uint16_t SWIFTMODULE_VERSION_MINOR = 672; // default expression type
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1376,6 +1376,7 @@ namespace decls_block {
     BCFixed<1>,              // isIsolated?
     BCFixed<1>,              // isCompileTimeConst?
     DefaultArgumentField,    // default argument kind
+    TypeIDField,             // default argument type
     BCBlob                   // default argument text
   >;
 

lib/Serialization/Serialization.cpp

@@ -3770,12 +3770,21 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     // any of the special ones.
     StringRef defaultArgumentText;
     SmallString<128> scratch;
+    // Type of the default expression.
+    Type defaultExprType;
+
     swift::DefaultArgumentKind argKind = param->getDefaultArgumentKind();
     if (argKind == swift::DefaultArgumentKind::Normal ||
-        argKind == swift::DefaultArgumentKind::StoredProperty)
+        argKind == swift::DefaultArgumentKind::StoredProperty) {
       defaultArgumentText =
         param->getDefaultValueStringRepresentation(scratch);
 
+      if (argKind == swift::DefaultArgumentKind::Normal) {
+        if (auto *defaultExpr = param->getTypeCheckedDefaultExpr())
+          defaultExprType = defaultExpr->getType();
+      }
+    }
+
     unsigned abbrCode = S.DeclTypeAbbrCodes[ParamLayout::Code];
     ParamLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
         S.addDeclBaseNameRef(param->getArgumentName()),
@@ -3789,6 +3798,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
         param->isIsolated(),
         param->isCompileTimeConst(),
         getRawStableDefaultArgumentKind(argKind),
+        S.addTypeRef(defaultExprType),
         defaultArgumentText);
 
     if (interfaceType->hasError() && !S.allowCompilerErrors()) {