From ed1773b26a2aa383ce61fef9551b881456375cf8 Mon Sep 17 00:00:00 2001
From: Anna Rift <anna.rift@hpe.com>
Date: Fri, 20 Dec 2024 11:09:08 -0800
Subject: [PATCH] Implement prim 'scalar promotion type'

Signed-off-by: Anna Rift <anna.rift@hpe.com>
---
 frontend/lib/resolution/prims.cpp        | 14 +++++++++++++-
 frontend/test/resolution/testResolve.cpp | 19 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/frontend/lib/resolution/prims.cpp b/frontend/lib/resolution/prims.cpp
index 1545b0390cd8..d8ca89aa440e 100644
--- a/frontend/lib/resolution/prims.cpp
+++ b/frontend/lib/resolution/prims.cpp
@@ -390,6 +390,18 @@ static QualifiedType primTypeof(Context* context, PrimitiveTag prim, const CallI
   return QualifiedType(QualifiedType::TYPE, typePtr);
 }
 
+static QualifiedType primPromotionType(Context* context, const CallInfo& ci) {
+  if (ci.numActuals() != 1) return QualifiedType();
+  auto actualQt = ci.actual(0).type();
+
+  auto promoTy = getPromotionType(context, actualQt).type();
+
+  // We want a type result, even if the prim was passed a value.
+  auto promoQt = QualifiedType(QualifiedType::TYPE, promoTy);
+
+  return promoQt;
+}
+
 static QualifiedType primGetSvecMember(Context* context, PrimitiveTag prim,
                                        const CallInfo& ci) {
   CHPL_ASSERT(prim == PRIM_GET_SVEC_MEMBER ||
@@ -1688,7 +1700,7 @@ CallResolutionResult resolvePrimCall(ResolutionContext* rc,
       break;
 
     case PRIM_SCALAR_PROMOTION_TYPE:
-      CHPL_UNIMPL("misc primitives");
+      type = primPromotionType(context, ci);
       break;
     case PRIM_STATIC_FIELD_TYPE:
       type = staticFieldType(context, ci);
diff --git a/frontend/test/resolution/testResolve.cpp b/frontend/test/resolution/testResolve.cpp
index 7ae6419ae3af..4cbe3621cff7 100644
--- a/frontend/test/resolution/testResolve.cpp
+++ b/frontend/test/resolution/testResolve.cpp
@@ -1739,6 +1739,23 @@ static void testInfiniteCycleBug() {
   std::ignore = resolveQualifiedTypeOfX(context, program1);
 }
 
+static void testPromotionPrim() {
+  Context* context = buildStdContext();
+  ErrorGuard guard(context);
+
+  std::string prog =
+    R"""(
+      var d : domain(1);
+      type t = __primitive("scalar promotion type", d);
+      param x = t == int;
+    )""";
+
+  auto x = resolveTypeOfXInit(context, prog);
+  ensureParamBool(x, true);
+
+  assert(guard.realizeErrors() == 0);
+}
+
 int main() {
   test1();
   test2();
@@ -1770,5 +1787,7 @@ int main() {
 
   testInfiniteCycleBug();
 
+  testPromotionPrim();
+
   return 0;
 }