Merging features/stackalloc-init into dev15.7.x

[VSadov]

As of #25382 , the feature branch meets requirements for the merge to the release branch.

The testplan is at: #25160

The IDE manual pass has been completed (see below).

[VSadov]

Testing tags

• 🔍 = Scenarios that are regularly tested against internal builds
• ⏩ = Scenarios that must work as expected before new language features are merged

When doing a test pass, copy this page and consider using these status indicators:

• ✅ = Tested & Approved (possibly with linked bugs)
• ❌ = Merge blocking
• 🚧 = Non-blocking bugs
• 🆗 = Issue has been fixed
• 🆓 = No expected impact
• ❓ = Open question

¹ Feature updated by compiler team, with appropriate unit tests.

² Feature requires more complete testing by IDE team.

Product Features

Core Scenarios in Editing, Navigating, and Viewing

Category	Feature/Description	C# Signoff/Notes	VB Signoff/Notes
Enable/Disable	⏩ Feature Flags To completely enables/disable new compiler features in the compiler & IDE	✅	N/A
Typing	⏩ General Typing - Type and paste new constructs - Nothing interferes with verbatim typing	✅	N/A
	🔍 ⏩ Completion - Typing new keyword/construct names - Dotting off of new constructs - Matching part of the identifier is highlighted (including word prefix matches) [Visual Studio 2015 Update 1] - Target type preselection [Visual Studio 2017] IntelliSense filtering [Visual Studio 2017]	✅	N/A
	⏩ Formatting - Spacing in and around new constructs - Spacing options - Format Document command Tools > Options settings should be respected	✅	N/A
	⏩ Automatic Brace Completion (C# only) - Auto-insert close brace - Shift+Enter commit of IntelliSense and any pending brace completion sessions (Known issue: #18065)	✅	N/A
	⏩ Indentation - Typing Enter in an unfinished statement indents the next line	✅	N/A
Navigating	🔍 ⏩ Go To Definition - F12 from callsites to definition - Ctrl+click [Visual Studio 2017 version 15.4]	✅	N/A
	⏩ Go To Implementation - Ctrl+F12 to jump from virtual members to their implementations - Jump from inheritable types to their implementations	✅	N/A
	🔍 ⏩ Find All References - Lists references to a symbol in "Find Symbol Results" window - Shows results in hierarchy grouped by definition [Visual Studio 2015] - Results should be groupable/filterable/classified appropriately [Visual Studio 2017] - Find All References on literals [Visual Studio 2017 version 15.3]	✅	N/A
Viewing	🔍 ⏩ Colorization - Keywords, literals, and identifiers colored appropriately in code - Colors should theme appropriately - The "Blue Theme (Additional Contrast)" should have sufficiently dark colors	✅	N/A
	⏩ Error Squiggles - Squiggles appear as expected on reasonable spans	✅	N/A

Code Transformations

Category	Feature/Description	C# Signoff/Notes	VB Signoff/Notes
Refactoring with UI	🔍 Inline Rename (with UI) - Dashboard shows correct information - Highlighted spans are updated appropriately - Rename operation updates the correct set of symbols	✅	N/A
	🔍 Change Signature (with UI) - Updates all direct & cascaded definitions/callsites - Shows appropriate signature & parameter previews in UI - Reorder and Remove in the same session [Visual Studio 2015]	✅	N/A
	🔍 Extract Interface (with UI) - Generated Interface has expected shape - UI shows appropriate method previews	N/A	N/A
	Generate Type (with UI) - Dialog gives all valid options	N/A	N/A
	Generate Overrides [Visual Studio 2017 version 15.3]	N/A	N/A
Refactorings	Rename Tracking - Tracking span tracks & dismisses as expected - Invokable from references [Visual Studio 2015]	✅	N/A
	🔍 Extract Method - Extracted method has the expected signature - All arguments/return values handled correctly - Extracted code block is reasonable - Automatically starts Inline Rename	✅	N/A
	Introduce Variable - Introduced variable has the expected signature and initializer expression - "Introduce for All" correctly finds dupes	N/A	N/A
	Inline Temporary Variable - Inlined values are appropriately expanded/reduced	N/A	N/A
	Organize Usings - Honors "Place 'System' namespace first" option	N/A	N/A
	Convert Get* Methods to Properties Add Description	✅	N/A
	🔍 Encapsulate Field - Select a field and convert it to a property backed by the field - Try selecting multiple fields at once	N/A	N/A
	Modifier Ordering [Visual Studio 2017 version 15.5]	N/A	N/A
	Convert ReferenceEquals to is null [Visual Studio 2017 version 15.5]	:N/A	N/A
	Add Missing Modifiers [Visual Studio 2017 version 15.5]	N/A	N/A
	Convert Lambda to Local Function [Visual Studio 2017 version 15.5]	N/A	N/A
	Move Declaration Near Reference [Visual Studio 2017 version 15.5]	N/A	N/A
	Introduce Pattern Matching [Visual Studio 2017 version 15.5]	N/A	N/A
	Simplify Inferred Tuple Names [Visual Studio 2017 version 15.5]	Requires C# 7.1 or greater N/A	N/A
	Convert keyword and symbol references to doc comment tags [Visual Studio 2017 version 15.5]	N/A	N/A
Fixes	Add Using - Triggers on appropriate constructs - Including NuGet references - Including Referenced Assemblies - Includes spelling fixes	N/A	N/A
	Generate Local - Select an expression and introduce a local variable to represent it - This should start an Inline Rename session	✅	N/A
	Generate Field - Select an expression and introduce a field to represent it - This should start an Inline Rename session	N/A	N/A
	Generate Method/Constructor - Call a nonexistent method or constructor to generate it from its usage - Generated method has the expected signature and accessibility - Add parameter to existing constructor from callsite [Visual Studio 2017 version 15.3]	N/A	N/A
	Generate Constructor from members - Select fields/properties to generate a constructor accepting corresponding arguments - Generated constructor has the expected signature and accessibility	N/A	N/A
	Implement Interface - Only missing methods added - All added methods have the expected signature and accessibility	✅	N/A
	Implement IDisposable - Implement IDisposable and you should see a large block of code properly implementing that particular interface	N/A	N/A
	Implement Abstract Class - Inherit from an abstract class, and you should be able to auto-generate all of the missing members	N/A	N/A
	Remove Unused Variables [Visual Studio 2017 version 15.3]	N/A	N/A
	Remove Unused Usings	N/A	N/A
	Sort Usings	N/A	N/A
	Convert Get Methods to Properties - Name a method GetStuff and convert it to a property called Stuff	N/A	N/A
	Make Method Async/Sync - Add an await to a synchronous method, you should be offered to add the async keyword - Remove all await keywords from an async method, you should be offered to remove the async keyword	N/A	N/A
	Use Object Initializer Over Property Assignment - Create a new instance of a type and then assign each of its properties on subsequent lines - You should be offered to convert that to an object initializer	N/A	N/A
	Insert Digit Separators [Visual Studio 2017 version 15.3]	N/A	N/A
Code Gen	🔍 Snippets - Tab completion, presence in completion list - Insertion via Snippet Picker UI (Ctrl + K, Ctrl + X) or (Ctrl + K, Ctrl + S) - (VB) Snippet Picker UI via ?<Tab> - (VB) Special snippet completion list (p?<esc><tab>)	N/A	N/A
	Event Hookup on Tab (C# only) - Type "+=" after an event name and QuickInfo shows - Invoking should pick good name & launch Inline Rename	N/A	N/A
	End Construct Generation (VB only) - Type Sub Test() and hit enter, the End Sub should be generated automatically	N/A	N/A
	Automatic End Construct Update (VB only) - Type Sub Test() and End Sub, changing Sub to Function in either one should update the other	N/A	N/A
	Spell checking - Type a name that's close to a variable name but off by a character or two - Lightbulb should have option to fix up the spelling - Includes type names that will require a using	N/A	N/A
	Move type to file - Lightbulb to move type to another file when the type name doesn't match the filename - Option to change the file name if the type doesn't match the file name	N/A	N/A
	Convert between properties and Get methods - Offers to change a method named GetStuff to a property named Stuff	N/A	N/A
	Convert auto property to full property [Visual Studio 2017 version 15.5]	N/A	N/A
	Add missing cases Use a switch on a strict subset of an Enum's members - It should offer to generate the rest of the cases	N/A	N/A
	Add null checks for parameters [Visual Studio 2017 version 15.3]	N/A	N/A
	Change base for numeric literals [Visual Studio 2017 version 15.3]	N/A	N/A
	Convert if to switch [Visual Studio 2017 version 15.3]	N/A	N/A
	Resolve git merge conflicts [Visual Studio 2017 version 15.3]	N/A	N/A
	Add argument name [Visual Studio 2017 version 15.3	N/A	N/A
	Fade and remove unreachable code [Visual Studio 2017 version 15.5]	N/A	N/A
	Add missing file banner [Visual Studio 2017 version 15.5]	N/A	N/A
	Deconstruct tuple declaration [Visual Studio 2017 version 15.4]	N/A	N/A

[VSadov]

@dotnet/roslyn-compiler - FYI

[VSadov]

CC:@jaredpar for the merge to dev15.7.x approval.

[VSadov]

@dotnet-bot test windows_debug_vs-integration_prtest please

[jaredpar]

Approved

[VSadov]

Thanks!!