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REPL: warn when a non-last module-level expression result is discarded (BT-979)#1022

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jamesc merged 1 commit intomainfrom
worktree-BT-979
Mar 1, 2026
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REPL: warn when a non-last module-level expression result is discarded (BT-979)#1022
jamesc merged 1 commit intomainfrom
worktree-BT-979

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@jamesc jamesc commented Feb 28, 2026 •
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Summary

  • Enable the effect-free statement lint on module.expressions by default, so REPL users see warnings when expression results are silently discarded (e.g., #{#x => 1} #{#y => 2} where the first map literal is discarded)
  • Add skip_module_expression_lint flag to CompilerOptions so bootstrap-test compilation can opt out (test fixtures intentionally use top-level expressions with // => assertions)
  • Expand REPL warning filter to include Severity::Lint diagnostics

Linear issue: https://linear.app/beamtalk/issue/BT-979

Key Changes

  • CompilerOptions gains skip_module_expression_lint: bool (default false)
  • check_effect_free_statements now checks module.expressions unless the flag is set
  • REPL compiler port surfaces Severity::Lint warnings to users
  • Bootstrap-test compilation sets the flag to true to suppress false positives
  • 4 new tests, 1 updated test, all 4,838 tests pass

Test plan

  • Existing effect-free lint tests pass
  • New module-level lint tests verify detection and opt-out
  • Bootstrap-test compilation doesn't produce false positives
  • Full CI passes (just ci)

🤖 Generated with Claude Code

Summary by CodeRabbit

  • Improvements
    • REPL now displays linting hints for effect-free statements, providing enhanced feedback during interactive development.
    • Adjusted compiler linting behavior for module-level expressions in test fixtures.

@jamesc @claude
feat: warn when non-last module-level expression result is discarded …
28bacd6 
…BT-979

- Enable effect-free lint check on module.expressions by default
- Add skip_module_expression_lint flag to CompilerOptions for bootstrap-test opt-out
- Include Severity::Lint in REPL compiler port warnings so users see the hint
- Add tests for module-level expression linting (default-on and opt-out)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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coderabbitai bot commented Feb 28, 2026 •
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📥 Commits

Reviewing files that changed from the base of the PR and between 213f695 and 28bacd6.

📒 Files selected for processing (7)
  • crates/beamtalk-cli/src/commands/test_stdlib.rs
  • crates/beamtalk-cli/src/main.rs
  • crates/beamtalk-compiler-port/src/main.rs
  • crates/beamtalk-core/src/lib.rs
  • crates/beamtalk-core/src/lint/effect_free_statement.rs
  • crates/beamtalk-core/src/semantic_analysis/mod.rs
  • crates/beamtalk-core/src/semantic_analysis/validators.rs
📝 Walkthrough

Walkthrough

Adds a new skip_module_expression_lint boolean field to CompilerOptions to conditionally suppress linting of top-level module expressions. The flag is threaded through the semantic analysis pipeline and set to true during test fixture compilation while defaulting to false elsewhere, allowing effect-free statement checks on module-level expressions to be opted out.

Changes

Cohort / File(s) Summary
CompilerOptions Struct Definition
crates/beamtalk-core/src/lib.rs		 Added public field skip_module_expression_lint: bool to control effect-free lint checks on module expressions (defaults to false).
Compilation Options Initialization
crates/beamtalk-cli/src/main.rs, crates/beamtalk-compiler-port/src/main.rs		 Updated CompilerOptions initialization to use ..Default::default() pattern and wired skip_module_expression_lint flag from options through compilation pipeline.
Effect-Free Statement Linting
crates/beamtalk-core/src/semantic_analysis/validators.rs, crates/beamtalk-core/src/lint/effect_free_statement.rs		 Updated check_effect_free_statements() signature to accept skip_module_expression_lint boolean parameter; added tests verifying module-level expression linting behavior with and without the flag.
Semantic Analysis Pipeline
crates/beamtalk-core/src/semantic_analysis/mod.rs		 Threaded skip_module_expression_lint flag through internal analyse_full() function and updated callers (analyse_with_options) to propagate the option from CompilerOptions.
Test Fixture Compilation
crates/beamtalk-cli/src/commands/test_stdlib.rs		 Set skip_module_expression_lint: true when compiling test fixtures to suppress module-level expression lint checks (BT-979).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

  • #990 — Introduces the effect-free-statement lint that this PR extends with conditional skipping of module-expression checks.
  • #994 — Refactors module expression traversal in validators.rs, directly affecting the same code paths modified here.
  • #992 — Modifies the semantic analysis pipeline entry point (analyse_full) to add a separate lint pass, sharing infrastructure with this PR's analysis-level changes.
🚥 Pre-merge checks | ✅ 3
✅ Passed checks (3 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly summarizes the main change: enabling linting to warn about discarded non-last module-level expressions in the REPL.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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@jamesc jamesc merged commit 38aef01 into main Mar 1, 2026
5 checks passed
@jamesc jamesc deleted the worktree-BT-979 branch March 1, 2026 08:05
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