Bug 303504 – REGRESSION(303805@main) GCC 12 build broken as the new generated RenderStyle::display() is not constexpr

• Component: WebCore Misc.
• Status: RESOLVED DUPLICATE

[Lauro Moura]

The GCC 12 stable bots for WPE and GTK broke after 303805@main with the following error:

```
In file included from ../../../Source/WebCore/rendering/style/RenderStyleSetters.h:29,
                 from WebCore/DerivedSources/StyleBuilderGenerated.cpp:8,
                 from WebCore/DerivedSources/unified-sources/UnifiedSource-3a52ce78-198.cpp:8:
../../../Source/WebCore/rendering/style/RenderStyleInlines.h: In member function ‘constexpr bool WebCore::RenderStyle::isDisplayRegionType() const’:
../../../Source/WebCore/rendering/style/RenderStyleInlines.h:228:19: error: call to non-‘constexpr’ function ‘WebCore::DisplayType WebCore::RenderStyle::display() const’
  228 |     return display() == DisplayType::Block
      |            ~~~~~~~^~
In file included from ../../../Source/WebCore/rendering/style/RenderStyleInlines.h:70:
WebCore/PrivateHeaders/WebCore/RenderStyleInlinesGenerated.h:63:20: note: ‘WebCore::DisplayType WebCore::RenderStyle::display() const’ declared here
   63 | inline DisplayType RenderStyle::display() const
      |                    ^~~~~~~~~~~
../../../Source/WebCore/rendering/style/RenderStyleInlines.h: In member function ‘constexpr bool WebCore::RenderStyle::doesDisplayGenerateBlockContainer() const’:
../../../Source/WebCore/rendering/style/RenderStyleInlines.h:270:33: error: call to non-‘constexpr’ function ‘WebCore::DisplayType WebCore::RenderStyle::display() const’
  270 |     auto display = this->display();
      |                    ~~~~~~~~~~~~~^~
<snip long list>
```

As commented by Claudio in the PR[1] earlier today, this is happening because `RenderStyle::display()` lost the constexpr tag as this method is now generated:

```
-    constexpr DisplayType display() const { return static_cast<DisplayType>(m_nonInheritedFlags.effectiveDisplay); }
+    inline DisplayType display() const;
```

[1] https://github.com/WebKit/WebKit/pull/54710#pullrequestreview-3534814541

[Lauro Moura]

*** This bug has been marked as a duplicate of bug 303398 ***