[daveedvdv-nvidia]

Fixes #423.

When an enclosing template is instantiated, a reference to one of its class-type nontype template parameters in the signature of a member template (or of a generic lambda) is replaced by the template parameter object. When the member template's own arguments were then substituted, make_operand_for_rescanned_identifier rebuilt that reference with make_constant_operand, i.e., as a prvalue rather than a const lvalue. Taking its address therefore made deduction fail (the examples in the issue), and other uses produced a function type inconsistent with that of the template:

struct NoConst { int operator()() { return 0; } };
template <auto F> struct S {
  template <typename T> static auto g(T t) -> decltype(t, F);
};
using R = decltype(S<NoConst{}>::g(0));
// Previously: "template instantiation resulted in unexpected function type
// of "auto (int)->const NoConst &"".

The part of make_template_param_object_operand that builds the const lvalue operand for a template parameter object is now a separate function, make_template_param_object_variable_operand, which the rescan uses instead.

Summary by CodeRabbit

• Bug Fixes
  • Corrected handling of class-type non-type template parameters in member-template and generic-lambda signatures. Address-taking, member access, and template argument deduction now work as expected in these cases.
  • Added regression coverage across C++20 compiler configurations to verify consistent behavior.

[coderabbitai]

No actionable comments were generated in the recent review.

Recent review info

Run configuration

• Source mode: Auto
• Repository: edgcpp/compiler
• Branch: main
• File: .coderabbit.yaml
• Commit: cc40804
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Advanced
• Run ID: 6e6ea0bc-e983-44a8-8986-b2f52138085c

Commits

Reviewing files that changed from the base of the PR and between cc40804 and 7b8ac81.

Files selected for processing: 9

• src/expr.c
• src/exprutil.c
• src/exprutil.h
• src/pending_changes/gh-423-template-param-object-member-template.txt
• tests/tests/regressions/.gh-423.rto/default.1.1.txt
• tests/tests/regressions/.gh-423.rto/default.2.1.txt
• tests/tests/regressions/.gh-423.rto/default.3.1.txt
• tests/tests/regressions/.gh-423.rto/default.4.1.txt
• tests/tests/regressions/gh-423.sft.cpp

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Walkthrough

The rescan fallback now creates an operand from a template parameter object variable instead of creating a constant operand. A regression test covers member-template and generic-lambda signatures that use class-type non-type template parameters.

Changes: Template parameter object rescanning

Layer / File(s)	Summary
Build operands from template parameter object variables src/expr.c, src/exprutil.c, src/exprutil.h	The rescan fallback calls the new variable-based operand helper. The existing operand function delegates operand construction to that helper.
Cover member-template and lambda signatures tests/tests/regressions/gh-423.sft.cpp, tests/tests/regressions/.gh-423.rto/*, src/pending_changes/gh-423-template-param-object-member-template.txt	The C++20 regression test checks member-template, generic-lambda, partial-specialization, and deduced-parameter cases. Runner fixtures specify C++20 compiler modes, and the pending-change entry describes the reported failures.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Possibly related PRs

• edgcpp/compiler#422: Both changes handle class-type non-type template parameters in signatures; this PR extends operand handling to rescanned enclosing-template references.
• edgcpp/compiler#435: Both changes address rescans of template and lambda signatures that refer to enclosing template parameters.
• edgcpp/compiler#339: Both changes cover lambda rescans involving enclosing template parameters.

Suggested labels: bug

Suggested reviewers: wchilders-nvidia, darkarc

Merge Risk: Minimal · up to 7b8ac

No actionable current-head defect remains from the reviewed changes.

Pre-merge checks: 4

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title names the main change: class-type non-type template parameter objects from enclosing templates, as referenced in member template signatures, and it cites the GH #423 issue. The raw summary a…
Linked Issues check		Issue #423 requires class-type NTTP references in enclosing-template member-template and generic-lambda signatures to remain const lvalues during substitution. src/expr.c now calls `make_template_pa…
Out of Scope Changes check		The changes stay within issue #423. The source changes extract and reuse template-parameter-object operand construction. The added pending-change note, regression source, and regression runner entries…

Full details: Title check

Explanation

The title names the main change: class-type non-type template parameter objects from enclosing templates, as referenced in member template signatures, and it cites the GH #423 issue. The raw summary and objectives confirm the change adds a variable-operand helper and corrects rescanning so these references are no longer rebuilt as prvalues. The title is specific and on-topic, so it passes.

Full details: Linked Issues check

Explanation

Issue #423 requires class-type NTTP references in enclosing-template member-template and generic-lambda signatures to remain const lvalues during substitution. src/expr.c now calls make_template_param_object_variable_operand during rescanning. src/exprutil.c constructs the const lvalue operand. The regression test tests/tests/regressions/gh-423.sft.cpp covers address-taking deduction, a generic lambda, a partial specialization, member access, and the reported auto NTTP case. The test includes compile-time type and value assertions for C++20 compiler modes.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #423. The source changes extract and reuse template-parameter-object operand construction. The added pending-change note, regression source, and regression runner entries document and test the same behavior. No unrelated product behavior or unrelated files appear in the reviewed diff.

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[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/exprutil.c	80.00%	0 Missing and 1 partial ⚠️

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[nv-cmeerw]

Looks good to me.