From 61c36671cb2ebc2e69503e3120a93ebff556c3af Mon Sep 17 00:00:00 2001
From: MikePopoloski <mike@popoloski.com>
Date: Fri, 1 Mar 2024 21:46:31 -0500
Subject: [PATCH] Tests and fixes for config param overriding

---
 source/ast/symbols/ParameterBuilder.cpp | 12 +++--
 tests/unittests/ast/ConfigTests.cpp     | 63 +++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/source/ast/symbols/ParameterBuilder.cpp b/source/ast/symbols/ParameterBuilder.cpp
index 5e02c29f0..29d36d5cc 100644
--- a/source/ast/symbols/ParameterBuilder.cpp
+++ b/source/ast/symbols/ParameterBuilder.cpp
@@ -26,6 +26,13 @@ ParameterBuilder::ParameterBuilder(const Scope& scope, std::string_view definiti
 
 void ParameterBuilder::setAssignments(const ParameterValueAssignmentSyntax& syntax,
                                       bool isFromConfig) {
+    // Special case for config param assignments: if the assignment
+    // syntax list is empty, we set all params back to their defaults.
+    if (isFromConfig && syntax.parameters.empty()) {
+        assignments.clear();
+        return;
+    }
+
     // Build up data structures to easily index the parameter assignments. We need to handle
     // both ordered assignment as well as named assignment, though a specific instance can only
     // use one method or the other.
@@ -103,11 +110,6 @@ void ParameterBuilder::setAssignments(const ParameterValueAssignmentSyntax& synt
                 continue;
             }
 
-            // It's allowed to have no initializer in the assignment;
-            // it means to just use the default.
-            if (!arg->expr)
-                continue;
-
             assignments[param.name] = {arg->expr, isFromConfig};
         }
 
diff --git a/tests/unittests/ast/ConfigTests.cpp b/tests/unittests/ast/ConfigTests.cpp
index af333ba17..77f1a0a8d 100644
--- a/tests/unittests/ast/ConfigTests.cpp
+++ b/tests/unittests/ast/ConfigTests.cpp
@@ -557,9 +557,64 @@ config cfg1;
     instance top use #(.WIDTH(32));
     instance top.a1 use #(.W(top.WIDTH));
 endconfig
+
+module top4 ();
+    parameter S = 16;
+    adder #(.ID("a1")) a1();
+    adder #(.ID("a2")) a2();
+    adder #(.ID("a3")) a3();
+    adder #(.ID("a4")) a4();
+endmodule
+
+config cfg2;
+    localparam S = 24;
+    design top4;
+    instance top4.a1 use #(.W(top4.S));
+    instance top4.a2 use #(.W(S));
+endconfig
+
+module top5 ();
+    parameter WIDTH = 64, DEPTH = 1024, ID = "A1";
+    adder #(.ID(ID), .W(WIDTH), .D(DEPTH)) a1();
+endmodule
+
+config cfg3;
+    design top5;
+    instance top5.a1 use #(.W());
+endconfig
+
+module top6 ();
+    adder #(.W(64), .D(1024)) a1();
+endmodule
+
+config cfg4;
+    design top6;
+    instance top6.a1 use #();
+endconfig
+
+module test;
+    top8 t();
+    defparam t.WIDTH = 64;
+    defparam t.a1.W = 16;
+endmodule
+
+module top8 ();
+    parameter WIDTH = 32;
+    adder #(.ID("a1")) a1();
+    adder #(.ID("a2"), .W(WIDTH)) a2();
+endmodule
+
+config cfg6;
+    design test;
+    instance test.t use #(.WIDTH(48));
+endconfig
 )");
     CompilationOptions options;
     options.topModules.emplace("cfg1");
+    options.topModules.emplace("cfg2");
+    options.topModules.emplace("cfg3");
+    options.topModules.emplace("cfg4");
+    options.topModules.emplace("cfg6");
 
     Compilation compilation(options);
     compilation.addSyntaxTree(tree);
@@ -572,4 +627,12 @@ endconfig
 
     CHECK(getParam("top.a1.W").integer() == 32);
     CHECK(getParam("top.a1.D").integer() == 512);
+    CHECK(getParam("top4.a1.W").integer() == 16);
+    CHECK(getParam("top4.a2.W").integer() == 24);
+    CHECK(getParam("top5.a1.W").integer() == 8);
+    CHECK(getParam("top5.a1.D").integer() == 1024);
+    CHECK(getParam("top6.a1.W").integer() == 8);
+    CHECK(getParam("top6.a1.D").integer() == 512);
+    CHECK(getParam("test.t.a1.W").integer() == 16);
+    CHECK(getParam("test.t.a2.W").integer() == 48);
 }