Add a general-purpose property bag to Compilation.

src/Compilers/Core/Portable/CodeAnalysis.csproj

@@ -51,6 +51,7 @@
     <Compile Include="Binding\AbstractLookupSymbolsInfo.cs" />
     <Compile Include="CaseInsensitiveComparison.cs" />
     <Compile Include="CodeGen\ILEmitStyle.cs" />
+    <Compile Include="Compilation\CompilationContext.cs" />
     <Compile Include="DiagnosticAnalyzer\AnalyzerDriver.CompilationData.cs" />
     <Compile Include="DiagnosticAnalyzer\SuppressMessageInfo.cs" />
     <Compile Include="Diagnostic\SuppressionInfo.cs" />

src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -32,6 +32,11 @@ namespace Microsoft.CodeAnalysis
     /// </summary>
     public abstract partial class Compilation
     {
+        /// <summary>
+        /// For use only in <see cref="Microsoft.CodeAnalysis.Collections.CompilationContext"/>.
+        /// </summary>
+        internal ConcurrentDictionary<object, object> _compilationContext = new ConcurrentDictionary<object, object>();
+
         /// <summary>
         /// Returns true if this is a case sensitive compilation, false otherwise.  Case sensitivity
         /// affects compilation features such as name lookup as well as choosing what names to emit

src/Compilers/Core/Portable/Compilation/CompilationContext.cs

@@ -0,0 +1,66 @@
+using System;
+
+namespace Microsoft.CodeAnalysis.Collections
+{
+    /// <summary>
+    /// A mutable typesafe dictionary from a pair of compilation and key (of type <see cref="CompilationContext.Key{T}"/>)
+    /// to a value (of type T). All keys and values associated with a compilation are reachable for GC purposes as a
+    /// consequence of this API for only as long as the compilation is reachable.
+    /// </summary>
+    public class CompilationContext
+    {
+        private static CompilationContext _instance = new CompilationContext();
+        public static CompilationContext Instance => _instance;
+        private CompilationContext() { }
+
+        public sealed class Key<T> { }
+
+        public bool TryGetValue<T>(Compilation compilation, Key<T> key, out T value)
+        {
+            if (compilation == null) throw new ArgumentNullException(nameof(compilation));
+            if (key == null) throw new ArgumentNullException(nameof(key));
+            object tempValue;
+            if (compilation._compilationContext.TryGetValue(key, out tempValue))
+            {
+                value = (T)tempValue;
+                return true;
+            }
+            else
+            {
+                value = default(T);
+                return false;
+            }
+        }
+
+        public bool TryAdd<T>(Compilation compilation, Key<T> key, T value)
+        {
+            if (compilation == null) throw new ArgumentNullException(nameof(compilation));
+            if (key == null) throw new ArgumentNullException(nameof(key));
+            return compilation._compilationContext.TryAdd(key, value);
+        }
+
+        public bool TryRemove<T>(Compilation compilation, Key<T> key, out T value)
+        {
+            if (compilation == null) throw new ArgumentNullException(nameof(compilation));
+            if (key == null) throw new ArgumentNullException(nameof(key));
+            object tempValue;
+            if (compilation._compilationContext.TryRemove(key, out tempValue))
+            {
+                value = (T)tempValue;
+                return true;
+            }
+            else
+            {
+                value = default(T);
+                return false;
+            }
+        }
+
+        public T GetOrAdd<T>(Compilation compilation, Key<T> key, T value)
+        {
+            if (compilation == null) throw new ArgumentNullException(nameof(compilation));
+            if (key == null) throw new ArgumentNullException(nameof(key));
+            return (T)compilation._compilationContext.GetOrAdd(key, value);
+        }
+    }
+}

src/Compilers/Core/Portable/PublicAPI.Unshipped.txt

@@ -1,12 +1,18 @@
 *REMOVED*static Microsoft.CodeAnalysis.SyntaxNodeExtensions.NormalizeWhitespace<TNode>(this TNode node, string indentation = "    ", bool elasticTrivia = false) -> TNode
+Microsoft.CodeAnalysis.Collections.CompilationContext
+Microsoft.CodeAnalysis.Collections.CompilationContext.GetOrAdd<T>(Microsoft.CodeAnalysis.Compilation compilation, Microsoft.CodeAnalysis.Collections.CompilationContext.Key<T> key, T value) -> T
+Microsoft.CodeAnalysis.Collections.CompilationContext.Key<T>
+Microsoft.CodeAnalysis.Collections.CompilationContext.TryAdd<T>(Microsoft.CodeAnalysis.Compilation compilation, Microsoft.CodeAnalysis.Collections.CompilationContext.Key<T> key, T value) -> bool
+Microsoft.CodeAnalysis.Collections.CompilationContext.TryGetValue<T>(Microsoft.CodeAnalysis.Compilation compilation, Microsoft.CodeAnalysis.Collections.CompilationContext.Key<T> key, out T value) -> bool
+Microsoft.CodeAnalysis.Collections.CompilationContext.TryRemove<T>(Microsoft.CodeAnalysis.Compilation compilation, Microsoft.CodeAnalysis.Collections.CompilationContext.Key<T> key, out T value) -> bool
 Microsoft.CodeAnalysis.CommandLineArguments.ScriptArguments.get -> System.Collections.Immutable.ImmutableArray<string>
 Microsoft.CodeAnalysis.CommandLineParser.IsInteractive.get -> bool
 Microsoft.CodeAnalysis.Compilation.GetSubmissionResultType(out bool hasValue) -> Microsoft.CodeAnalysis.ITypeSymbol
 Microsoft.CodeAnalysis.Compilation.PreviousSubmission.get -> Microsoft.CodeAnalysis.Compilation
 Microsoft.CodeAnalysis.Compilation.ScriptClass.get -> Microsoft.CodeAnalysis.INamedTypeSymbol
 Microsoft.CodeAnalysis.Compilation.WithPreviousSubmission(Microsoft.CodeAnalysis.Compilation newPreviousSubmission) -> Microsoft.CodeAnalysis.Compilation
-Microsoft.CodeAnalysis.CompilationOptions.ReportSuppressedDiagnostics.get -> bool
 Microsoft.CodeAnalysis.CompilationOptions.Deterministic.get -> bool
+Microsoft.CodeAnalysis.CompilationOptions.ReportSuppressedDiagnostics.get -> bool
 Microsoft.CodeAnalysis.CompilationOptions.WithReportSuppressedDiagnostics(bool value) -> Microsoft.CodeAnalysis.CompilationOptions
 Microsoft.CodeAnalysis.Diagnostic.GetSuppressionInfo(Microsoft.CodeAnalysis.Compilation compilation) -> Microsoft.CodeAnalysis.Diagnostics.SuppressionInfo
 Microsoft.CodeAnalysis.DiagnosticDescriptor.GetEffectiveSeverity(Microsoft.CodeAnalysis.CompilationOptions compilationOptions) -> Microsoft.CodeAnalysis.ReportDiagnostic
@@ -54,6 +60,7 @@ Microsoft.CodeAnalysis.StrongNameProvider.StrongNameProvider() -> void
 abstract Microsoft.CodeAnalysis.Diagnostic.IsSuppressed.get -> bool
 abstract Microsoft.CodeAnalysis.ParseOptions.CommonWithKind(Microsoft.CodeAnalysis.SourceCodeKind kind) -> Microsoft.CodeAnalysis.ParseOptions
 override Microsoft.CodeAnalysis.SyntaxTree.ToString() -> string
+static Microsoft.CodeAnalysis.Collections.CompilationContext.Instance.get -> Microsoft.CodeAnalysis.Collections.CompilationContext
 static Microsoft.CodeAnalysis.Diagnostic.Create(string id, string category, Microsoft.CodeAnalysis.LocalizableString message, Microsoft.CodeAnalysis.DiagnosticSeverity severity, Microsoft.CodeAnalysis.DiagnosticSeverity defaultSeverity, bool isEnabledByDefault, int warningLevel, bool isSuppressed, Microsoft.CodeAnalysis.LocalizableString title = null, Microsoft.CodeAnalysis.LocalizableString description = null, string helpLink = null, Microsoft.CodeAnalysis.Location location = null, System.Collections.Generic.IEnumerable<Microsoft.CodeAnalysis.Location> additionalLocations = null, System.Collections.Generic.IEnumerable<string> customTags = null, System.Collections.Immutable.ImmutableDictionary<string, string> properties = null) -> Microsoft.CodeAnalysis.Diagnostic
 static Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzerExtensions.WithAnalyzers(this Microsoft.CodeAnalysis.Compilation compilation, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer> analyzers, Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzersOptions analysisOptions) -> Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers
 static Microsoft.CodeAnalysis.Diagnostics.Telemetry.AnalyzerTelemetry.GetAnalyzerActionCountsAsync(this Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers compilationWithAnalyzers, Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer analyzer, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Diagnostics.Telemetry.AnalyzerTelemetry.ActionCounts>
@@ -62,4 +69,4 @@ static Microsoft.CodeAnalysis.SyntaxNodeExtensions.NormalizeWhitespace<TNode>(th
 static Microsoft.CodeAnalysis.SyntaxNodeExtensions.NormalizeWhitespace<TNode>(this TNode node, string indentation, bool elasticTrivia) -> TNode
 virtual Microsoft.CodeAnalysis.MetadataReferenceResolver.ResolveMissingAssemblies.get -> bool
 virtual Microsoft.CodeAnalysis.MetadataReferenceResolver.ResolveMissingAssembly(Microsoft.CodeAnalysis.AssemblyIdentity identity) -> Microsoft.CodeAnalysis.PortableExecutableReference
-virtual Microsoft.CodeAnalysis.SourceReferenceResolver.ReadText(string resolvedPath) -> Microsoft.CodeAnalysis.Text.SourceText
+virtual Microsoft.CodeAnalysis.SourceReferenceResolver.ReadText(string resolvedPath) -> Microsoft.CodeAnalysis.Text.SourceText