From 903ed2acb95eff18d704aa8d09d637fd06fc2b37 Mon Sep 17 00:00:00 2001
From: MikePopoloski <mike@popoloski.com>
Date: Sat, 5 Oct 2024 15:25:23 -0400
Subject: [PATCH] Allow unpacked unions in equality and conditional expressions

---
 source/ast/expressions/OperatorExpressions.cpp | 14 ++++++++++++--
 tests/unittests/ast/EvalTests.cpp              |  3 +++
 tests/unittests/ast/ExpressionTests.cpp        | 11 ++++-------
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/source/ast/expressions/OperatorExpressions.cpp b/source/ast/expressions/OperatorExpressions.cpp
index 4d18ff71c..d578ebadf 100644
--- a/source/ast/expressions/OperatorExpressions.cpp
+++ b/source/ast/expressions/OperatorExpressions.cpp
@@ -847,7 +847,7 @@ Expression& BinaryExpression::fromComponents(Expression& lhs, Expression& rhs, B
                     contextDetermined(context, result->right_, result, compilation.getStringType(),
                                       opRange);
                 }
-                else if (lt->isAggregate() && lt->isEquivalent(*rt) && !lt->isUnpackedUnion()) {
+                else if (lt->isAggregate() && lt->isEquivalent(*rt)) {
                     good = !isWildcard;
                     result->type = singleBitType(compilation, lt, rt);
                 }
@@ -1342,7 +1342,7 @@ Expression& ConditionalExpression::fromSyntax(Compilation& comp,
             else
                 good = false;
         }
-        else if (lt->isEquivalent(*rt) && !lt->isUnpackedUnion()) {
+        else if (lt->isEquivalent(*rt)) {
             result->type = lt;
         }
         else if (left.isImplicitString() && right.isImplicitString()) {
@@ -2615,6 +2615,16 @@ ConstantValue Expression::evalBinaryOperator(BinaryOperator op, const ConstantVa
                 SLANG_UNREACHABLE;
         }
     }
+    else if (cvl.isUnion() && cvr.isUnion()) {
+        switch (op) {
+            OP(Equality, SVInt(cvl == cvr));
+            OP(Inequality, SVInt(cvl != cvr));
+            OP(CaseEquality, SVInt(cvl == cvr));
+            OP(CaseInequality, SVInt(cvl != cvr));
+            default:
+                SLANG_UNREACHABLE;
+        }
+    }
 
 #undef OP
     SLANG_UNREACHABLE;
diff --git a/tests/unittests/ast/EvalTests.cpp b/tests/unittests/ast/EvalTests.cpp
index 233a3e551..48833babb 100644
--- a/tests/unittests/ast/EvalTests.cpp
+++ b/tests/unittests/ast/EvalTests.cpp
@@ -841,6 +841,9 @@ union {
     session.eval("baz.c = 123;");
     CHECK(session.eval("baz.a.s1").integer() == 123);
 
+    CHECK(session.eval("foo == bar").integer() == 1);
+    CHECK(session.eval("1 ? foo : bar").toString() == "(0) [3,4,42]");
+
     NO_SESSION_ERRORS;
 }
 
diff --git a/tests/unittests/ast/ExpressionTests.cpp b/tests/unittests/ast/ExpressionTests.cpp
index a98f19a97..204a8107a 100644
--- a/tests/unittests/ast/ExpressionTests.cpp
+++ b/tests/unittests/ast/ExpressionTests.cpp
@@ -336,12 +336,12 @@ TEST_CASE("Expression types") {
 
     // Unpacked unions
     declare("union { int i; real r; } uu1, uu2;");
-    CHECK(typeof("uu1 == uu2") == "<error>");
-    CHECK(typeof("uu1 !== uu2") == "<error>");
-    CHECK(typeof("1 ? uu1 : uu2") == "<error>");
+    CHECK(typeof("uu1 == uu2") == "bit");
+    CHECK(typeof("uu1 !== uu2") == "bit");
+    CHECK(typeof("1 ? uu1 : uu2") == "union{int i;real r;}u$3");
 
     auto diags = filterWarnings(compilation.getAllDiagnostics());
-    REQUIRE(diags.size() == 11);
+    REQUIRE(diags.size() == 8);
     CHECK(diags[0].code == diag::BadUnaryExpression);
     CHECK(diags[1].code == diag::BadBinaryExpression);
     CHECK(diags[2].code == diag::BadBinaryExpression);
@@ -350,9 +350,6 @@ TEST_CASE("Expression types") {
     CHECK(diags[5].code == diag::BadBinaryExpression);
     CHECK(diags[6].code == diag::BadConditionalExpression);
     CHECK(diags[7].code == diag::NotBooleanConvertible);
-    CHECK(diags[8].code == diag::BadBinaryExpression);
-    CHECK(diags[9].code == diag::BadBinaryExpression);
-    CHECK(diags[10].code == diag::BadConditionalExpression);
 }
 
 TEST_CASE("Expression - bad name references") {