Add an experimental flag-gated in-process compile path for hot reload sessions

FSharp.slnx

@@ -43,6 +43,11 @@
       <BuildType Solution="Proto|*" Project="Release" />
     </Project>
   </Folder>
+  <Folder Name="/Tests/HotReloadDemo/">
+    <Project Path="tests/projects/HotReloadDemo/HotReloadDemoApp/HotReloadDemoApp.fsproj">
+      <BuildType Solution="Proto|*" Project="Debug" />
+    </Project>
+  </Folder>
   <Folder Name="/Tests/FSharp.Compiler.Service.Tests support/">
     <Project Path="tests/service/data/CSharp_Analysis/CSharp_Analysis.csproj">
       <BuildType Solution="Proto|*" Project="Debug" />

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -23,7 +23,7 @@
 * Fix internal error (FS0193) when calling an indexed property setter with a named argument that matches an indexer parameter. ([Issue #16034](https://github.com/dotnet/fsharp/issues/16034), [PR #19851](https://github.com/dotnet/fsharp/pull/19851))
 * Fix missing FS1182 ("unused binding") warning for unused `let` function bindings inside class types. ([Issue #13849](https://github.com/dotnet/fsharp/issues/13849), [PR #19805](https://github.com/dotnet/fsharp/pull/19805))
 * Fix internal compiler error FS1110 in `task { let! }` (and other computation expressions) when a generic IL extension method whose `this`-parameter is a method-level type variable is in scope (e.g. `open ReactiveUI`). Regression from PR #19536. ([Issue #19936](https://github.com/dotnet/fsharp/issues/19936))
-* Fix inner mutually-recursive `let rec ... and ...` functions under `--realsig+` not being lifted to top-level static methods (TLR), causing `FSharpFunc` closure allocations and loss of `tail.` opcodes — the large struct-mutual-recursion perf regression reported in [Issue #17607](https://github.com/dotnet/fsharp/issues/17607). ([PR #19882](https://github.com/dotnet/fsharp/pull/19882))
+* Fix inner mutually-recursive `let rec ... and ...` functions under `--realsig+` not being lifted to top-level static methods (TLR), causing `FSharpFunc` closure allocations and loss of `tail.` opcodes - the large struct-mutual-recursion perf regression reported in [Issue #17607](https://github.com/dotnet/fsharp/issues/17607). ([PR #19882](https://github.com/dotnet/fsharp/pull/19882))
 * Fix `TypeLoadException` ("Specialize tried to implicitly override a method with weaker type parameter constraints") and the related CLR crash with constrained inline calls by stripping constraints from closure-class typars in `EraseClosures.convIlxClosureDef`. ([Issue #14492](https://github.com/dotnet/fsharp/issues/14492), [Issue #19075](https://github.com/dotnet/fsharp/issues/19075), [PR #19882](https://github.com/dotnet/fsharp/pull/19882))
 * Fix `FieldAccessException` at runtime when the optimizer relocates a read of a `protected` (family) base-class field into a method outside the field's family (e.g. a trivial member inlined into module/startup code under `--optimize+`). Protected (family) IL field access is no longer hoisted out of its declaring family by inlining or method-splitting. ([Issue #19963](https://github.com/dotnet/fsharp/issues/19963), [PR #19964](https://github.com/dotnet/fsharp/pull/19964))
 
@@ -128,6 +128,10 @@
 
 ### Added
 
+* Added internal synthesized-name replay infrastructure for compiler-generated names, preserving normal compilation output while enabling future hot reload name stability work.
+* Add an internal typed-tree diff utility for future F# hot reload edit classification. It is not called by normal compilation. ([PR #19941](https://github.com/dotnet/fsharp/pull/19941))
+* Added internal F# hot reload delta emitter and symbol matcher infrastructure with direct emitter test coverage.
+* Added an experimental, internal, flag-gated in-process compile path for hot reload sessions. `FSHARP_HOTRELOAD_INPROCESS_COMPILE` refreshes the output assembly and PDB from the latest checked project before delta emission, while `FSHARP_HOTRELOAD_INCREMENTAL_EMIT` enables a nested per-file optimized-tree cache.
 * Added `FSharpMemberOrFunctionOrValue.IsPropertyAccessor` convenience property that returns true for compiler-generated property accessors (`get_X` / `set_X`). ([Issue #18157](https://github.com/dotnet/fsharp/issues/18157), [PR #19883](https://github.com/dotnet/fsharp/pull/19883))
 * Added warning FS3884 when a function or delegate value is used as an interpolated string argument. ([PR #19289](https://github.com/dotnet/fsharp/pull/19289))
 * Symbols: add ObsoleteDiagnosticInfo ([PR #19359](https://github.com/dotnet/fsharp/pull/19359))
@@ -140,6 +144,10 @@
 * Checker: recover on checking language version ([PR ##19970](https://github.com/dotnet/fsharp/pull/19970))
 * Implied argument names for function-to-delegate coercions now fall back to the delegate's `Invoke` parameter names when the function has no recoverable names (e.g. a partial application like `System.Func<int, int>((+) 1)`), instead of synthetic `delegateArg0`, `delegateArg1`, … names. ([PR #20001](https://github.com/dotnet/fsharp/pull/20001))
 * Add internal `ResetCompilerGeneratedNameState` to `CompilerGlobalState` name generators so warm-checker re-compilation can produce fresh-process-identical generated names. ([PR #20017](https://github.com/dotnet/fsharp/pull/20017))
+* Add Roslyn-format EnC CustomDebugInformation codec and portable PDB method CDI emission support to AbstractIL. ([PR #20018](https://github.com/dotnet/fsharp/pull/20018))
+* Add internal ECMA-335 Edit-and-Continue metadata delta writer to AbstractIL. ([PR #20019](https://github.com/dotnet/fsharp/pull/20019))
+* Add internal `ResetCompilerGeneratedNameState` to `CompilerGlobalState` name generators so warm-checker re-compilation can produce fresh-process-identical generated names. ([PR #20017](https://github.com/dotnet/fsharp/pull/20017))
+* Add experimental hot reload support: `--test:HotReloadDeltas` baseline capture in fsc, EnC metadata/IL/PDB delta emission, rude-edit detection, and an `FSharpChecker` session API (`CreateHotReloadSession`, with `AddProject`/`EmitDelta`/`Commit`/`Discard`). Off by default; flag-off compilation is unchanged. ([Issue #11636](https://github.com/dotnet/fsharp/issues/11636), [PR #19941](https://github.com/dotnet/fsharp/pull/19941))
 
 ### Improved
 
@@ -151,4 +159,4 @@
 * Exception field serialization (`GetObjectData` and field-restoring constructor) is now gated behind `langversion:11` (`LanguageFeature.ExceptionFieldSerializationSupport`). With langversion ≤10, exception codegen is unchanged from pre-#19342 behavior. ([PR #19746](https://github.com/dotnet/fsharp/pull/19746))
 
 ### Breaking Changes
-* Optimizer: don't inline named functions in debug builds ([PR #19548](https://github.com/dotnet/fsharp/pull/19548)
+* Optimizer: don't inline named functions in debug builds ([PR #19548](https://github.com/dotnet/fsharp/pull/19548)

release-notes.md

@@ -18,6 +18,7 @@ These release notes track our current efforts to document changes to the F# proj
 
 ### FSharp Compiler Service (main)
 
+* Added internal hot reload baseline reading for recorded EnC state and synthesized-name snapshot PDB data.
 * In FSharpParsingOptions, rename ConditionalCompilationDefines --> ConditionalDefines
 * Some syntax tree nodes have changed, e.g. introduction of SyntaxTree trivia
 * Resolved expressions (FSharpExpr) now reveal debug points, you must match them explicitly using `DebugPoint(dp, expr)`