Add granular inlay hint suppression options for better noise reduction

[Copilot]

Inlay hints currently show everywhere with limited options to suppress them when context makes them redundant. This adds four new suppression capabilities to reduce visual noise while preserving hints for ambiguous cases.

Changes

Parameter hints - flexible name matching

• SuppressForParametersThatMatchArgumentName now ignores case and underscores
• fooBar parameter now matches _fooBar, FooBar, FOO_BAR arguments

Parameter hints - bidirectional suffix matching

• SuppressForParametersThatDifferOnlyBySuffix now works both directions
• Suppresses hints for fooBar ↔ fooBar_ and fooBarX ↔ fooBar

Parameter hints - member access matching

• New option: SuppressForParametersThatMatchMemberName
• Suppresses when member access matches parameter name (case-insensitive)

Vector2 bar = new(foo.X, foo.Y);  // No hints shown for x/y parameters

Type hints - target-typed suppression

• New options: SuppressForTargetTypedNew, SuppressForTargetTypedCollectionExpressions
• Suppresses type hints when type is locally apparent from declaration

Vector2 foo = new(1, 2);     // No hint for Vector2
int[] bar = [1, 2, 3];       // No hint for int[]

All new options default to enabled to reduce clutter out-of-the-box.

Implementation notes

• NormalizeIdentifier() strips leading _/@ and all underscores, then uses case-insensitive comparison
• ParameterDiffersOnlyBySuffix() handles individual argument/parameter pairs, distinct from existing ParametersDifferOnlyBySuffix() which checks if all parameters in a call share the same prefix pattern
• IsTargetTyped() detects variable declarations, assignments, and return statements where type flows from context

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Improve inlay hint suppression options</issue_title>
<issue_description>## Is your feature request related to a problem? Please describe.
I find inlay hints extremely useful, but when enabled, they show up everywhere, and the options to suppress them when they're not necessary are very lacking

Describe the solution you would like

dotnet.inlayHints.suppressInlayHintsForParametersThatMatchArgumentName should (or have an option to) ignore case and punctuation:

void fn(int fooBar) { }

// Hidden:
fn(fooBar);

// Not hidden:
fn(/*fooBar: */_fooBar);
fn(/*fooBar: */FooBar);
fn(/*fooBar: */FOO_BAR);

dotnet.inlayHints.suppressInlayHintsForParametersThatDifferOnlyBySuffix doesn't seem to work at all:

fn(/*fooBar: */fooBar_);

void fn2(int fooBar_) { }

fn2(/*fooBar_: */fooBar);

There should be an option to hide inlay hints for parameters ending with a member access that matches argument name:

Vector2 bar = new(/*x: */foo.X, /*y: */foo.Y);

There should be an option to hide inlay hints for collection indexer parameters:

someArr[/*index: */i];

And there should be an option to hide locally apparent type hints for target-typed new and collection expressions:

// Caused by `csharp.inlayHints.enableInlayHintsForImplicitObjectCreation`:
Vector2 foo = new/*Vector2*/(1, 2);

// Caused by `csharp.inlayHints.enableInlayHintsForTypes`:
int[] bar = /*int[]*/[1, 2, 3];

These options would reduce the clutter of unneeded hints while keeping hints for more ambiguous cases

Applicable Scenarios

When someone is using inlay hints for parameters, implicit object creation, and types</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Improve inlay hint suppression options vscode-csharp#8862

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[CyrusNajmabadi]

Remember that all options are things we have to effectively maintain forever. Let's just make sure that anything we're adding is something we feel is very sensible and has reasonable semantics and clarity that is sufficient for the ecosystem.

I'm generally ok with more in this area. I just want to avoid us getting into option-explosion land.

[JoeRobich]

Let's just make sure that anything we're adding is something we feel is very sensible and has reasonable semantics and clarity that is sufficient for the ecosystem.

@CyrusNajmabadi How about a SuppressHintWhenApparent?

[CyrusNajmabadi]

I like that. It definitely gives us flexibility to adjust things in the future

[akhera99]

/pr-val

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