Improve generic type argument inference. (#3370)

* Improve generic type argument inference.

* Fix.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/source/slang/slang-ast-val.cpp b/source/slang/slang-ast-val.cpp
index e860e1ec6..d1408a3fc 100644
--- a/source/slang/slang-ast-val.cpp
+++ b/source/slang/slang-ast-val.cpp
@@ -286,6 +286,11 @@ Val* DeclaredSubtypeWitness::_resolveImplOverride()
     return this;
 }
 
+ConversionCost DeclaredSubtypeWitness::_getOverloadResolutionCostOverride()
+{
+    return kConversionCost_GenericParamUpcast;
+}
+
 Val* DeclaredSubtypeWitness::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int * ioDiff)
 {
     if (auto genConstraintDeclRef = getDeclRef().as<GenericTypeConstraintDecl>())
@@ -431,6 +436,11 @@ Val* TransitiveSubtypeWitness::_substituteImplOverride(ASTBuilder* astBuilder, S
     return astBuilder->getTransitiveSubtypeWitness(substSubToMid, substMidToSup);
 }
 
+ConversionCost TransitiveSubtypeWitness::_getOverloadResolutionCostOverride()
+{
+    return getSubToMid()->getOverloadResolutionCost() + getMidToSup()->getOverloadResolutionCost();
+}
+
 void TransitiveSubtypeWitness::_toTextOverride(StringBuilder& out)
 {
     // Note: we only print the constituent
@@ -471,6 +481,17 @@ Val* ExtractFromConjunctionSubtypeWitness::_substituteImplOverride(ASTBuilder* a
         substSub, substSup, substWitness, getIndexInConjunction());
 }
 
+ConversionCost ExtractFromConjunctionSubtypeWitness::_getOverloadResolutionCostOverride()
+{
+    auto witness = as<ConjunctionSubtypeWitness>(getConjunctionWitness());
+    if (!witness)
+        return kConversionCost_None;
+    auto index = getIndexInConjunction();
+    if (index < witness->getComponentCount())
+        return witness->getComponentWitness(index)->getOverloadResolutionCost();
+    return kConversionCost_None;
+}
+
 // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ExtractExistentialSubtypeWitness !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
 void ExtractExistentialSubtypeWitness::_toTextOverride(StringBuilder& out)
@@ -541,6 +562,14 @@ Val* ConjunctionSubtypeWitness::_substituteImplOverride(ASTBuilder* astBuilder,
     return result;
 }
 
+ConversionCost ConjunctionSubtypeWitness::_getOverloadResolutionCostOverride()
+{
+    ConversionCost result = kConversionCost_None;
+    for (Index i = 0; i < getComponentCount(); i++)
+        result += getComponentWitness(i)->getOverloadResolutionCost();
+    return result;
+}
+
 void ExtractFromConjunctionSubtypeWitness::_toTextOverride(StringBuilder& out)
 {
     out << "ExtractFromConjunctionSubtypeWitness(";