Report a better error when lookup finds a package when expecting a value

scripts/diagnostics.txt

@@ -853,6 +853,7 @@ error DotIntoInstArray "object is an array so expecting an index here, not a dot
 error UnresolvedForwardTypedef "forward typedef '{}' does not resolve to a data type"
 error DefinitionUsedAsType "'{}' is {} definition but is used like a type"
 error DefinitionUsedAsValue "'{}' is {} definition but is used as a value"
+error UndeclaredButFoundPackage "'{}' is a package, did you mean to use '::' here?"
 error AutoVariableHierarchical "cannot refer to automatic variable via hierarchical reference"
 error TypeHierarchical "cannot refer to type names via hierarchical reference"
 error NonStaticClassProperty "invalid use of non-static class property '{}'"

source/ast/Lookup.cpp

@@ -2169,8 +2169,7 @@ void Lookup::reportUndeclared(const Scope& initialScope, std::string_view name,
     }
 
     // Otherwise, check if this names a definition, in which case we can give a nicer error.
-    auto def = initialScope.getCompilation().getDefinition(name, initialScope);
-    if (def) {
+    if (auto def = comp.getDefinition(name, initialScope)) {
         if (isHierarchical) {
             result.addDiag(initialScope, diag::CouldNotResolveHierarchicalPath, range) << name;
         }
@@ -2182,6 +2181,12 @@ void Lookup::reportUndeclared(const Scope& initialScope, std::string_view name,
         return;
     }
 
+    // Also check for a package with this name.
+    if (auto pkg = comp.getPackage(name)) {
+        result.addDiag(initialScope, diag::UndeclaredButFoundPackage, range.end()) << name << range;
+        return;
+    }
+
     // Count the number of times we've performed typo correction.
     comp.didTypoCorrection();
 

tests/unittests/ast/LookupTests.cpp

@@ -2045,3 +2045,21 @@ endmodule
     REQUIRE(diags.size() == 1);
     CHECK(diags[0].code == diag::DotIntoInstArray);
 }
+
+TEST_CASE("Undeclared identifier -- package correction") {
+    auto tree = SyntaxTree::fromText(R"(
+package my_pkg;
+endpackage
+
+module m;
+    int i = my_pkg;
+endmodule
+)");
+
+    Compilation compilation;
+    compilation.addSyntaxTree(tree);
+
+    auto& diags = compilation.getAllDiagnostics();
+    REQUIRE(diags.size() == 1);
+    CHECK(diags[0].code == diag::UndeclaredButFoundPackage);
+}