Add diagnostic warning levels (-Wall/-Wextra/-Wpedantic)

[expipiplus1]

Fixes #11012.

Motivation

The diagnostic system had no notion of warning "levels": every warning was either always on, or had to be individually disabled with -Wno-<id>. There was no way to group advisory/stylistic warnings the way clang/gcc do with -Wall/-Wextra/-Wpedantic.

Proposed solution

Add clang/gcc-style warning groups. Following that model the groups are independent (not nested): a warning tagged with a group is emitted only when that group is enabled, while untagged warnings stay in the always-on default group. Most warnings need no annotation; only opt-in warnings are tagged.

A warning is tagged in slang-diagnostics.lua by passing an all/extra/pedantic sentinel positionally to warning(), alongside its spans:

warning("keyword-used-as-name", 20103,
    "keyword used as a name",
    span { loc = "location", message = "..." },
    pedantic)

The level rides on DiagnosticInfo and gating happens in one place, DiagnosticSink::getEffectiveMessageSeverity. Explicit per-id overrides (-W<name>/-Wno-<name>/-warnings-as-errors) continue to take precedence over group gating.

Control is exposed via the -Wall/-Wextra/-Wpedantic CLI flags and the WarningLevel compiler-API option (SlangWarningLevel).

Staging — pedantic is enabled by default for now. As the first example, keyword-used-as-name (E20103) is tagged pedantic: using a type keyword as a name is legal and usually works, so it is a style/portability hint rather than a likely bug. To avoid silently dropping any warning from today's output, the pedantic group is enabled by default in this PR, so tagging only records the group and changes nothing observable yet. A follow-up will flip pedantic to off-by-default and assign groups to the rest of the catalog.

Change summary

File	Change
include/slang.h	New SlangWarningLevel enum (Default/All/Extra/Pedantic) and CompilerOptionName::WarningLevel = 155 (appended; intValue0 is the group to enable, repeatable).
source/compiler-core/slang-diagnostic-sink.h	New internal WarningLevel enum (static-asserted against the public one), a level field on DiagnosticInfo (defaulted so existing aggregate/DIAGNOSTIC(...) initializers keep compiling), enableWarningLevel/isWarningLevelEnabled, and the enabled-groups bitmask (pedantic on by default for now).
source/compiler-core/slang-diagnostic-sink.cpp	Gate opt-in warnings in getEffectiveMessageSeverity; keep an explicit "enable" override for grouped warnings (see Process report).
source/slang/slang-diagnostics-helpers.lua	Define the all/extra/pedantic sentinels, recognise them in add_diagnostic, carry level through to the processed entry, and export them.
source/slang/slang-diagnostics.lua	Import the sentinels; tag keyword-used-as-name as pedantic.
source/slang/slang-rich-diagnostics.h.lua / .cpp	getWarningLevelEnum mapping and emit the level as the 5th DiagnosticInfo field.
source/slang/slang-options.cpp	Register -Wall/-Wextra/-Wpedantic (one option, three names) and map each to a WarningLevel group value.
source/slang/slang-compiler-options.cpp	Apply the WarningLevel option array to the sink in applySettingsToDiagnosticSink.
tests/diagnostics/warning-levels.slang	End-to-end test of the flag wiring and -Wno precedence.

Concepts and vocabulary

• Warning group / level: the all/extra/pedantic bucket a warning belongs to, mirroring the clang/gcc groups. Default is the implicit always-on group.
• DiagnosticInfo: the static descriptor for each diagnostic (id, severity, name, message — now also level). The Lua catalog generates these for the rich diagnostics; the compiler-core DIAGNOSTIC(...) macro catalogs generate the rest.
• getEffectiveMessageSeverity: the single chokepoint (used by both the legacy and rich diagnostic paths) that resolves a diagnostic's nominal severity into its effective severity after pragmas, per-id overrides, group gating, and warnings-as-errors.
• per-id override (m_severityOverrides): the map behind -W<name>/-Wno-<name>/-warnings-as-errors, keyed by diagnostic id.

Process report

Where the level lives, and why. The Lua catalog is the single source of truth for diagnostics, so the group is declared there and flows to DiagnosticInfo::level. The sink reads info.level directly rather than maintaining a side table. The level field has a default member initializer (WarningLevel::Default); this is what lets the existing 4-element aggregate initializers — both the Lua-generated ones and the DIAGNOSTIC(id, severity, name, msg) macro catalogs in compiler-core — keep compiling unchanged.

Gating. In getEffectiveMessageSeverity, after the existing pragma-tracker step, a warning whose group is not enabled is lowered to Severity::Disable. This sits in the else of the per-id-override check, so an explicit -W<name>/-Wno-<name> always wins over group gating.

One cascading fix — keeping the enable override for grouped warnings. overrideDiagnosticSeverity previously dropped any override equal to the diagnostic's nominal severity. With groups that is wrong: a warning whose group is off has an effective default of "suppressed", so an explicit -W<name> enabling it back to Warning is meaningful and must be kept, otherwise group gating would re-suppress it. The fix restricts the "remove when equal to default" shortcut to WarningLevel::Default diagnostics, where the nominal and effective defaults still coincide.

Input-shape check for the CLI handler. The three flags are registered as a single option with three names, so only -Wall/-Wextra/-Wpedantic ever reach the WarningLevel case; any other spelling is a wiring bug, so the fall-through asserts via SLANG_UNEXPECTED. Exact-match option lookup takes priority over the -W<id> prefix, so these are never confused with -W<name>.

Example chosen conservatively, and no behavior change yet. Only keyword-used-as-name is tagged. Because the pedantic group is on by default in this PR, the warning still appears exactly as before (its existing test passes unchanged), and the new warning-levels.slang test confirms the flags are accepted and that -Wno-keyword-used-as-name still suppresses it. Flipping pedantic off-by-default and grouping the rest of the catalog is intentionally left to follow-up, per the issue.

[coderabbitai]

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📝 Walkthrough

Walkthrough

Adds warning-level grouping across the diagnostic API, Lua diagnostics pipeline, CLI option handling, sink filtering, and validation tests. It tags keyword-used-as-name as pedantic, wires -Wall/-Wextra/-Wpedantic, and adds unit and integration tests for grouped warning behavior.

Changes

Warning Level Groups

Layer / File(s)	Summary
Public API and sink contracts include/slang.h, source/compiler-core/slang-diagnostic-sink.h	Adds public and internal warning-level enums, extends DiagnosticInfo with level, and adds sink enable/query APIs plus the enabled-level bitmask.
Lua diagnostics and rich output source/slang/slang-diagnostics-helpers.lua, source/slang/slang-rich-diagnostics.h.lua, source/slang/slang-rich-diagnostics.cpp, source/slang/slang-diagnostics.lua	Adds warning-level sentinels, records and exports diagnostic levels, maps them for rich diagnostics output, and marks keyword-used-as-name as pedantic.
CLI option parsing and application source/slang/slang-options.cpp, source/slang/slang-compiler-options.cpp, docs/user-guide/08-compiling.md	Registers WarningLevel, parses -Wall/-Wextra/-Wpedantic, applies them to DiagnosticSink, and documents the option.
Severity gating in DiagnosticSink source/compiler-core/slang-diagnostic-sink.cpp	Suppresses warnings when their level is disabled and retains per-id overrides for opt-in warning groups.
Diagnostic validation tests tools/slang-unit-test/unit-test-diagnostic-warning-level.cpp, tests/diagnostics/warning-levels.slang	Adds unit coverage for warning-level gating and integration coverage for pedantic diagnostics, CLI flag behavior, and per-warning suppression.

Related issue: #11012
Suggested reviewers: bmillsNV

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding diagnostic warning levels and the -Wall/-Wextra/-Wpedantic flags.
Description check	✅ Passed	The description matches the changeset and explains the warning-level groups, flags, and default pedantic behavior.
Linked Issues check	✅ Passed	The PR implements diagnostic warning levels, CLI flags, and grouping/default behavior requested by #11012.
Out of Scope Changes check	✅ Passed	The changes stay focused on warning-level support, tests, and docs without unrelated additions.

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[Copilot]

Pull request overview

This PR adds clang/gcc-style diagnostic warning groups to Slang, allowing opt-in “advisory/stylistic” warnings via -Wall / -Wextra / -Wpedantic (and the corresponding public compiler option), while keeping untagged warnings always-on by default.

Changes:

• Introduces a public SlangWarningLevel and CompilerOptionName::WarningLevel, plus an internal WarningLevel carried on DiagnosticInfo.
• Implements warning-group gating in DiagnosticSink::getEffectiveMessageSeverity, while preserving per-diagnostic overrides (-W… / -Wno-…) precedence.
• Adds CLI parsing for -Wall / -Wextra / -Wpedantic and an end-to-end regression test covering group gating and override behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
include/slang.h	Adds public SlangWarningLevel and new CompilerOptionName::WarningLevel.
source/compiler-core/slang-diagnostic-sink.h	Adds internal WarningLevel, DiagnosticInfo::level, and sink enable/query helpers + bitmask.
source/compiler-core/slang-diagnostic-sink.cpp	Implements group gating in effective severity resolution; adjusts override retention logic for grouped warnings.
source/slang/slang-diagnostics-helpers.lua	Adds/export warning-level sentinels and propagates level through diagnostic processing.
source/slang/slang-diagnostics.lua	Imports sentinels and tags implicit-conversion-to-double as pedantic.
source/slang/slang-rich-diagnostics.h.lua	Adds mapping from Lua warning-level strings to C++ WarningLevel enums.
source/slang/slang-rich-diagnostics.cpp	Emits the warning level into generated DiagnosticInfo initializers for rich diagnostics.
source/slang/slang-options.cpp	Registers -Wall/-Wextra/-Wpedantic and maps spellings to SlangWarningLevel option values.
source/slang/slang-compiler-options.cpp	Applies the (repeatable) WarningLevel option array to the diagnostic sink.
tests/diagnostics/warning-levels.slang	Adds an end-to-end test covering default suppression, group enable, per-id enable, and -Wno precedence.

[coderabbitai]

Actionable comments posted: 4

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

source/slang/slang-diagnostics-helpers.lua (1)

392-406: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Handle warning-level sentinels before binding primary_span.

Locationless diagnostics are allowed, but this parser only recognizes is_warning_level inside .... A call like warning("foo", 1, "msg", pedantic) leaves pedantic in primary_span, so the diagnostic stays in the default group and the entry shape becomes invalid.

Suggested fix

 local function add_diagnostic(name, code, severity, message, primary_span, ...)
+  local level = "default"
+  if primary_span and primary_span.is_warning_level then
+    level = primary_span.level
+    primary_span = nil
+  end
+
   local diag = {
     name = name,
     code = code,
     severity = severity,
     message = message,
     primary_span = primary_span,
-    -- Warning group; "default" (always emitted) unless a sentinel below overrides it.
-    level = "default",
+    -- Warning group; "default" (always emitted) unless a sentinel overrides it.
+    level = level,
   }
@@
     for _, s in ipairs(extra_spans) do
       if s.is_warning_level then
+        if diag.level ~= "default" then
+          error("diagnostic '" .. name .. "' specifies more than one warning level")
+        end
         -- A warning-level sentinel (all/extra/pedantic): record the group and skip it; it is
         -- not a span or note.
         diag.level = s.level

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Reviewing files that changed from the base of the PR and between 51959e2 and 7a52885.

📒 Files selected for processing (10)

• include/slang.h
• source/compiler-core/slang-diagnostic-sink.cpp
• source/compiler-core/slang-diagnostic-sink.h
• source/slang/slang-compiler-options.cpp
• source/slang/slang-diagnostics-helpers.lua
• source/slang/slang-diagnostics.lua
• source/slang/slang-options.cpp
• source/slang/slang-rich-diagnostics.cpp
• source/slang/slang-rich-diagnostics.h.lua
• tests/diagnostics/warning-levels.slang

[coderabbitai]

Actionable comments posted: 1

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📒 Files selected for processing (3)

• source/compiler-core/slang-diagnostic-sink.h
• source/slang/slang-diagnostics.lua
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[coderabbitai]

Actionable comments posted: 2

---

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📒 Files selected for processing (6)

• docs/user-guide/08-compiling.md
• source/compiler-core/slang-diagnostic-sink.h
• source/slang/slang-compiler-options.cpp
• source/slang/slang-diagnostics.lua
• tests/diagnostics/warning-levels.slang
• tools/slang-unit-test/unit-test-diagnostic-warning-level.cpp

[github-actions]

Verdict: 🟡 Minor — 1 gap

Adds clang/gcc-style warning groups (WarningLevel::Default/All/Extra/Pedantic) to DiagnosticSink with -Wall/-Wextra/-Wpedantic CLI flags and a public CompilerOptionName::WarningLevel = 155. Gating lives in getEffectiveMessageSeverity; per-id -W<name>/-Wno-<name> overrides win over group gating (with a corresponding fix in overrideDiagnosticSeverity so a -W<name> restoring the nominal severity is not stripped for grouped warnings). Pedantic is on by default as a staging step; only keyword-used-as-name (E20103) is tagged so far.

Changes Overview

Diagnostic sink infrastructure (source/compiler-core/slang-diagnostic-sink.{h,cpp})

• New WarningLevel enum with static_asserts mirroring the public SLANG_WARNING_LEVEL_*. DiagnosticInfo gains a level field (default Default for aggregate-init compat). DiagnosticSink gains enableWarningLevel/isWarningLevelEnabled (bounds-check < 32 before shift), get/setEnabledWarningLevels, an m_enabledWarningLevels bitmask initialized with Pedantic bit set, and parent-sink inheritance of the bitmask. getEffectiveMessageSeverity gates warnings after per-id overrides; overrideDiagnosticSeverity keeps overrides equal to default severity when the diagnostic is in an opt-in group.

Option plumbing (source/slang/slang-compiler-options.cpp, slang-options.cpp, include/slang.h)

• New public SlangWarningLevel enum and CompilerOptionName::WarningLevel = 155 (appended before CountOf). CLI parser maps -Wall/-Wextra/-Wpedantic via string comparison; applySettingsToDiagnosticSink iterates the (allow-duplicate) WarningLevel option array and calls enableWarningLevel for values in {ALL, EXTRA, PEDANTIC}, silently ignoring others.

Lua diagnostic generation (source/slang/slang-diagnostics-helpers.lua, slang-diagnostics.lua, slang-rich-diagnostics.h.lua, slang-rich-diagnostics.cpp)

• Positional all/extra/pedantic sentinels in warning()/err() set diag.level; add_diagnostic recognises them via is_warning_level. Rich-diagnostics template emits WarningLevel::X as the fifth DiagnosticInfo initializer via a new getWarningLevelEnum helper that errors on unknown level names.

Tests (tests/diagnostics/warning-levels.slang, tools/slang-unit-test/unit-test-diagnostic-warning-level.cpp)

• Six unit tests: default gating, additive enabling, per-id override precedence, warnings-as-errors interaction, parent-sink inheritance, out-of-range safety. One .slang file with five slangc runs (default, -Wpedantic, -Wall, -Wextra, all-three, -Wno-<id>).

Docs (docs/command-line-slangc-reference.md, docs/user-guide/08-compiling.md)

• New CLI reference section and new WarningLevel row in the CompilerOptionValue table.

Findings (1 total)

Severity	Location	Finding
🟡 Gap	docs/command-line-slangc-reference.md:260-266	File is auto-generated; hand-authored section diverges from what slangc -help-style markdown -h produces from the registration in slang-options.cpp.