From c92f1a36f00d6a70e18c896b6a4f2644457bd50f Mon Sep 17 00:00:00 2001
From: MikePopoloski <mike@popoloski.com>
Date: Sat, 19 Oct 2024 18:12:41 -0400
Subject: [PATCH] Fix connection of interface arrays to ports with different
 declared dimensions

---
 source/ast/symbols/PortSymbols.cpp     | 23 +++++++++++++++++++++--
 tests/unittests/ast/InterfaceTests.cpp | 22 ++++++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/source/ast/symbols/PortSymbols.cpp b/source/ast/symbols/PortSymbols.cpp
index 71ec46aa7..c1ee69a84 100644
--- a/source/ast/symbols/PortSymbols.cpp
+++ b/source/ast/symbols/PortSymbols.cpp
@@ -1111,6 +1111,25 @@ class PortConnectionBuilder {
         return true;
     }
 
+    const Symbol* rewireIfaceArrayIndices(const Symbol* sym, std::string_view name,
+                                          SourceLocation loc,
+                                          std::span<const ConstantRange> portDims) {
+        if (!sym || sym->kind != SymbolKind::InstanceArray)
+            return sym;
+
+        // The port dimensions are guaranteed to have the same count and width as
+        // the instance array dimensions but their indices may differ, so this
+        // function creates a new array with the correct range.
+        SLANG_ASSERT(!portDims.empty());
+        auto subPortDims = portDims.subspan(1);
+
+        SmallVector<const Symbol*> newElems;
+        for (auto elem : sym->as<InstanceArraySymbol>().elements)
+            newElems.push_back(rewireIfaceArrayIndices(elem, ""sv, loc, subPortDims));
+
+        return comp.emplace<InstanceArraySymbol>(comp, name, loc, newElems.copy(comp), portDims[0]);
+    }
+
     PortConnection::IfaceConn getInterfaceConn(ASTContext& context, const InterfacePortSymbol& port,
                                                const ExpressionSyntax& syntax) {
         SLANG_ASSERT(!port.isInvalid());
@@ -1169,7 +1188,7 @@ class PortConnectionBuilder {
         // Make the connection if the dimensions match exactly what the port is expecting.
         const Symbol* symbol = expr->as<ArbitrarySymbolExpression>().symbol;
         if (areDimSizesEqual(*portDims, dims))
-            return {symbol, modport};
+            return {rewireIfaceArrayIndices(symbol, port.name, port.location, *portDims), modport};
 
         // Otherwise, if the instance being instantiated is part of an array of instances *and*
         // the symbol we're connecting to is an array of interfaces, we need to check to see whether
@@ -1198,7 +1217,7 @@ class PortConnectionBuilder {
                 symbol = array.elements[size_t(index)];
             }
 
-            return {symbol, modport};
+            return {rewireIfaceArrayIndices(symbol, port.name, port.location, *portDims), modport};
         }
 
         auto& diag = scope.addDiag(diag::PortConnDimensionsMismatch, syntax.sourceRange())
diff --git a/tests/unittests/ast/InterfaceTests.cpp b/tests/unittests/ast/InterfaceTests.cpp
index 402ec8a6d..c17443e67 100644
--- a/tests/unittests/ast/InterfaceTests.cpp
+++ b/tests/unittests/ast/InterfaceTests.cpp
@@ -724,3 +724,25 @@ endmodule
     REQUIRE(diags.size() == 1);
     CHECK(diags[0].code == diag::UndeclaredIdentifier);
 }
+
+TEST_CASE("Iface array with different declared indices regress -- GH #1152") {
+    auto tree = SyntaxTree::fromText(R"(
+interface bus();
+	logic a;
+	logic b;
+endinterface
+
+module submodule(bus iface [3:2]);
+	assign iface[2].a = iface[3].b;
+endmodule
+
+module top();
+	bus iface[1:0]();
+	submodule inst(iface);
+endmodule
+)");
+
+    Compilation compilation;
+    compilation.addSyntaxTree(tree);
+    NO_COMPILATION_ERRORS;
+}