Merge dev16.0-preview2-vs-deps to master-vs-deps

docs/Language Feature Status.md

@@ -25,6 +25,7 @@ efforts behind them.
 | [Alternative interpolated verbatim strings](https://github.com/dotnet/csharplang/issues/1630) | master | Merged to dev16 preview1 | [jcouv](https://github.com/jcouv) | [cston](https://github.com/cston) | [jcouv](https://github.com/jcouv)
 | [stackalloc in nested contexts](https://github.com/dotnet/csharplang/issues/1412) | [nested-stackalloc](https://github.com/dotnet/roslyn/tree/features/nested-stackalloc) | [In Progress](https://github.com/dotnet/roslyn/issues/28968) | [gafter](https://github.com/gafter) | - | [gafter](https://github.com/gafter)
 | [Unmanaged generic structs](https://github.com/dotnet/csharplang/issues/1744) | master | [In Progress](https://github.com/dotnet/roslyn/issues/31374) | [RikkiGibson](https://github.com/RikkiGibson) | - | [jaredpar](https://github.com/jaredpar) |
+| [Static local functions](https://github.com/dotnet/csharplang/issues/1565) | master | [Implemented](https://github.com/dotnet/roslyn/issues/32069) | [cston](https://github.com/cston) | [jaredpar](https://github.com/jaredpar) | [jcouv](https://github.com/jcouv)
 
 # VB 16.0
 

docs/features/async-streams.md

@@ -125,7 +125,7 @@ See more details about those types at https://blogs.msdn.microsoft.com/dotnet/20
 
 Compared to the state machine for a regular async method, the `MoveNext()` for an async-iterator method adds logic:
 - to support handling a `yield return` statement, which saves the current value and fulfills the promise with result `true`,
-- to support handling a `yield break` statement, which sets the dispose mode on and jumps to the closest `finally` or exit,
+- to support handling a `yield break` statement, which sets the dispose mode on and jumps to the enclosing `finally` or exit,
 - to dispatch execution to `finally` blocks (when disposing),
 - to exit the method, which fulfills the promise with result `false`,
 - to catch exceptions, which set the exception into the promise.
@@ -168,12 +168,13 @@ IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken token)
     {StateMachineType} result;
     if (initialThreadId == /*managedThreadId*/ && state == StateMachineStates.FinishedStateMachine)
     {
-        state = StateMachineStates.NotStartedStateMachine;
+        state = InitialState; // -3
+        disposeMode = false;
         result = this;
     }
     else
     {
-        result = new {StateMachineType}(StateMachineStates.NotStartedStateMachine);
+        result = new {StateMachineType}(InitialState);
     }
     /* copy all of the parameter proxies */
 }
@@ -197,26 +198,26 @@ In contrast, async methods continue running autonomously until they are done. Th
 
 In summary, disposal of an async-iterator works based on four design elements:
 - `yield return` (jumps to finally when resuming in dispose mode)
-- `yield break` (enters dispose mode and jumps to finally)
-- `finally` (after a `finally` we jump to the next one)
+- `yield break` (enters dispose mode and jumps to enclosing finally)
+- `finally` (after a `finally` we jump to the next enclosing one)
 - `DisposeAsync` (enters dispose mode and resumes execution)
 
 The caller of an async-iterator method should only call `DisposeAsync()` when the method completed or was suspended by a `yield return`.
 `DisposeAsync` sets a flag on the state machine ("dispose mode") and (if the method wasn't completed) resumes the execution from the current state.
 The state machine can resume execution from a given state (even those located within a `try`).
-When the execution is resumed in dispose mode, it jumps straight to the relevant `finally`.
+When the execution is resumed in dispose mode, it jumps straight to the enclosing `finally`.
 `finally` blocks may involve pauses and resumes, but only for `await` expressions. As a result of the restrictions imposed on `yield return` (described above), dispose mode never runs into a `yield return`.
-Once a `finally` block completes, the execution in dispose mode jumps to the next relevant `finally`, or the end of the method once we reach the top-level.
+Once a `finally` block completes, the execution in dispose mode jumps to the next enclosing `finally`, or the end of the method once we reach the top-level.
 
-Reaching a `yield break` also sets the dispose mode flag and jumps to the next relevant `finally` (or end of the method).
+Reaching a `yield break` also sets the dispose mode flag and jumps to the enclosing `finally` (or end of the method).
 By the time we return control to the caller (completing the promise as `false` by reaching the end of the method) all disposal was completed,
 and the state machine is left in finished state. So `DisposeAsync()` has no work left to do.
 
 Looking at disposal from the perspective of a given `finally` block, the code in that block can get executed:
 - by normal execution (ie. after the code in the `try` block),
 - by raising an exception inside the `try` block (which will execute the necessary `finally` blocks and terminate the method in Finished state),
-- by calling `DisposeAsync()` (which resumes execution in dispose mode and jumps to the relevant finally),
-- following a `yield break` (which enters dispose mode and jumps to the relevant finally),
+- by calling `DisposeAsync()` (which resumes execution in dispose mode and jumps to the enclosing finally),
+- following a `yield break` (which enters dispose mode and jumps to the enclosing finally),
 - in dispose mode, following a nested `finally`.
 
 A `yield return` is lowered as:
@@ -240,16 +241,19 @@ disposeMode = true;
 ```C#
 ValueTask IAsyncDisposable.DisposeAsync()
 {
-    disposeMode = true;
-    if (state == StateMachineStates.FinishedStateMachine ||
-        state == StateMachineStates.NotStartedStateMachine)
+    if (state >= StateMachineStates.NotStartedStateMachine /* -1 */)
+    {
+        throw new NotSupportedException();
+    }
+    if (state == StateMachineStates.FinishedStateMachine /* -2 */)
     {
         return default;
     }
+    disposeMode = true;
     _valueOrEndPromise.Reset();
     var inst = this;
     _builder.Start(ref inst);
-    return new ValueTask(this, _valueOrEndPromise.Version); // note this leverages the state machine's implementation of IValueTaskSource
+    return new ValueTask(this, _valueOrEndPromise.Version);  // note this leverages the state machine's implementation of IValueTaskSource
 }
 ```
 
@@ -286,39 +290,46 @@ finallyEntryLabel:
 }
 ```
 
-In both cases, we will add a `if (disposeMode) /* jump to next finally or exit */` after the block for `finally` logic.
+In both cases, we will add a `if (disposeMode) /* jump to enclosing finally or exit */` after the block for `finally` logic.
 
 #### State values and transitions
 
 The enumerable starts with state -2.
-Calling GetAsyncEnumerator sets the state to -1, or returns a fresh enumerator (also with state -1).
+Calling GetAsyncEnumerator sets the state to -3, or returns a fresh enumerator (also with state -3).
 
 From there, MoveNext will either:
-- reach the end of the method (-2)
-- reach a `yield break` (-1, dispose mode = true)
-- reach a `yield return` or `await` (N)
+- reach the end of the method (-2, we're done and disposed)
+- reach a `yield break` (state unchanged, dispose mode = true)
+- reach a `yield return` (-N, decreasing from -4)
+- reach an `await` (N, increasing from 0)
 
-From suspended state N, MoveNext will resume execution (-1).
-But if the suspension was a `yield return`, you could also call DisposeAsync, which resumes execution (-1) in dispose mode.
+From suspended state N or -N, MoveNext will resume execution (-1).
+But if the suspension was a `yield return` (-N), you could also call DisposeAsync, which resumes execution (-1) in dispose mode.
 
 When in dispose mode, MoveNext continues to suspend (N) and resume (-1) until the end of the method is reached (-2).
 
+The result of invoking `DisposeAsync` from states -1 or N is unspecified. This compiler throws `NotSupportException` for those cases.
+
 ```
-   GetAsyncEnumerator    suspension (yield return, await)
--2 -----------------> -1 -------------------------------> N
- ^                   |  ^                                 |   Dispose mode = false
- | done and disposed |  |          resuming               |
- +-------------------+  +---------------------------------+
- |                   |                                    |
- |                   |                                    |
- |             yield |                                    |
- |             break |           DisposeAsync             |
- |                   |  +---------------------------------+
- |                   |  |
- |                   |  |
- | done and disposed v  v     suspension (await)
- +------------------- -1 -------------------------------> N
-                        ^                                 |   Dispose mode = true
-                        |          resuming               |
-                        +---------------------------------+
+        DisposeAsync                              await
+ +------------------------+             +------------------------> N
+ |                        |             |                          |
+ v   GetAsyncEnumerator   |             |        resuming          |
+-2 --------------------> -3 --------> -1 <-------------------------+    Dispose mode = false
+ ^                                   |  |                          |
+ |         done and disposed         |  |      yield return        |
+ +-----------------------------------+  +-----------------------> -N
+ |                                   |                             |
+ |                                   |                             |
+ |                             yield |                             |
+ |                             break |           DisposeAsync      |
+ |                                   |  +--------------------------+
+ |                                   |  |
+ |                                   |  |
+ |         done and disposed         v  v    suspension (await)
+ +----------------------------------- -1 ------------------------> N
+                                        ^                          |    Dispose mode = true
+                                        |         resuming         |
+                                        +--------------------------+
 ```
+

src/Compilers/CSharp/Portable/Binder/Binder_NameConflicts.cs

@@ -1,12 +1,7 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System.Collections.Immutable;
-using System.Diagnostics;
-using System.Linq;
-using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
-using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Collections;
 using Microsoft.CodeAnalysis.PooledObjects;
 
 namespace Microsoft.CodeAnalysis.CSharp
@@ -33,6 +28,7 @@ private static Location GetLocation(Symbol symbol)
         internal void ValidateParameterNameConflicts(
             ImmutableArray<TypeParameterSymbol> typeParameters,
             ImmutableArray<ParameterSymbol> parameters,
+            bool allowShadowingNames,
             DiagnosticBag diagnostics)
         {
             PooledHashSet<string> tpNames = null;
@@ -51,7 +47,7 @@ internal void ValidateParameterNameConflicts(
                     {
                         // Type parameter declaration name conflicts are detected elsewhere
                     }
-                    else
+                    else if (!allowShadowingNames)
                     {
                         ValidateDeclarationNameConflictsInScope(tp, diagnostics);
                     }
@@ -81,7 +77,7 @@ internal void ValidateParameterNameConflicts(
                         // The parameter name '{0}' is a duplicate
                         diagnostics.Add(ErrorCode.ERR_DuplicateParamName, GetLocation(p), name);
                     }
-                    else
+                    else if (!allowShadowingNames)
                     {
                         ValidateDeclarationNameConflictsInScope(p, diagnostics);
                     }
@@ -95,30 +91,41 @@ internal void ValidateParameterNameConflicts(
         /// <remarks>
         /// Don't call this one directly - call one of the helpers.
         /// </remarks>
-        protected bool ValidateNameConflictsInScope(Symbol symbol, Location location, string name, DiagnosticBag diagnostics)
+        private bool ValidateNameConflictsInScope(Symbol symbol, Location location, string name, DiagnosticBag diagnostics)
         {
             if (string.IsNullOrEmpty(name))
             {
                 return false;
             }
 
-            bool error = false;
+            bool allowShadowing = Compilation.IsFeatureEnabled(MessageID.IDS_FeatureStaticLocalFunctions);
+
             for (Binder binder = this; binder != null; binder = binder.Next)
             {
                 // no local scopes enclose members
-                if (binder is InContainerBinder || error)
+                if (binder is InContainerBinder)
                 {
-                    break;
+                    return false;
                 }
 
                 var scope = binder as LocalScopeBinder;
-                if (scope != null)
+                if (scope?.EnsureSingleDefinition(symbol, name, location, diagnostics) == true)
+                {
+                    return true;
+                }
+
+                // If shadowing is enabled, avoid checking for conflicts outside of local functions.
+                if (allowShadowing)
                 {
-                    error |= scope.EnsureSingleDefinition(symbol, name, location, diagnostics);
+                    var containingMethod = (binder as InMethodBinder)?.ContainingMemberOrLambda as MethodSymbol;
+                    if (containingMethod?.MethodKind == MethodKind.LocalFunction)
+                    {
+                        return false;
+                    }
                 }
             }
 
-            return error;
+            return false;
         }
     }
 }

src/Compilers/CSharp/Portable/Binder/Binder_Patterns.cs

@@ -167,7 +167,7 @@ internal BoundConstantPattern BindConstantPattern(
                 convertedExpression = new BoundConversion(
                     convertedExpression.Syntax, convertedExpression, Conversion.NoConversion, isBaseConversion: false, @checked: false,
                     explicitCastInCode: false, constantValueOpt: constantValueOpt, conversionGroupOpt: default, type: CreateErrorType(), hasErrors: true)
-                    { WasCompilerGenerated = true };
+                { WasCompilerGenerated = true };
             }
 
             return new BoundConstantPattern(node, convertedExpression, constantValueOpt ?? ConstantValue.Bad, inputType, hasErrors);
@@ -796,7 +796,7 @@ private static FieldSymbol CheckIsTupleElement(SyntaxNode node, NamedTypeSymbol
 
             if (foundElement is null || foundElement.TupleElementIndex != tupleIndex)
             {
-                diagnostics.Add(ErrorCode.ERR_TupleElementNameMismatch, node.Location, name, $"Item{tupleIndex+1}");
+                diagnostics.Add(ErrorCode.ERR_TupleElementNameMismatch, node.Location, name, $"Item{tupleIndex + 1}");
             }
 
             return foundElement;