Don't offer 'convert if to condition' if it crosses a directive

src/EditorFeatures/CSharpTest/UseConditionalExpression/UseConditionalExpressionForReturnTests.cs

@@ -821,6 +821,26 @@ IEnumerable<bool> M(int a)
     {
         yield return a != 0;
     }
+}");
+        }
+
+        [WorkItem(36117, "https://github.com/dotnet/roslyn/issues/36117")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseConditionalExpression)]
+        public async Task TestMissingWhenCrossingPreprocessorDirective()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"
+class C
+{
+    int M()
+    {
+        bool check = true;
+#if DEBUG
+        [||]if (check)
+            return 3;
+#endif
+        return 2;
+    }
 }");
         }
     }

src/Features/Core/Portable/UseConditionalExpression/AbstractUseConditionalExpressionDiagnosticAnalyzer.cs

@@ -39,8 +39,7 @@ protected sealed override void InitializeWorker(AnalysisContext context)
         private void AnalyzeOperation(OperationAnalysisContext context)
         {
             var ifOperation = (IConditionalOperation)context.Operation;
-            var ifStatement = ifOperation.Syntax as TIfStatementSyntax;
-            if (ifStatement == null)
+            if (!(ifOperation.Syntax is TIfStatementSyntax ifStatement))
             {
                 return;
             }

src/Features/Core/Portable/UseConditionalExpression/ForReturn/UseConditionalExpressionForReturnHelpers.cs

@@ -35,8 +35,7 @@ internal static class UseConditionalExpressionForReturnHelpers
 
             if (falseStatement == null)
             {
-                var parentBlock = ifOperation.Parent as IBlockOperation;
-                if (parentBlock == null)
+                if (!(ifOperation.Parent is IBlockOperation parentBlock))
                 {
                     return false;
                 }

src/Features/Core/Portable/UseConditionalExpression/UseConditionalExpressionHelpers.cs

 // 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;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editing;
-using Microsoft.CodeAnalysis.Formatting;
-using Microsoft.CodeAnalysis.Formatting.Rules;
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Operations;
-using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.UseConditionalExpression
 {
@@ -23,9 +14,21 @@ internal static class UseConditionalExpressionHelpers
             ISyntaxFactsService syntaxFacts, IConditionalOperation ifOperation,
             IOperation whenTrue, IOperation whenFalse)
         {
-            // Will likely screw things up if the if directive spans any preprocessor directives.
-            // So do not offer for now.
-            if (syntaxFacts.SpansPreprocessorDirective(ifOperation.Syntax))
+            // Will likely screw things up if the if directive spans any preprocessor directives. So
+            // do not offer for now.  Note: we pass in both the node for the ifOperation and the
+            // whenFalse portion.  The whenFalse portion isn't necessary under the ifOperation.  For
+            // example in:
+            //
+            //  ```c#
+            //  #if DEBUG
+            //  if (check)
+            //      return 3;
+            //  #endif  
+            //  return 2;
+            //  ```
+            //
+            // In this case, we want to see that this cross the `#endif`
+            if (syntaxFacts.SpansPreprocessorDirective(ifOperation.Syntax, whenFalse.Syntax))
             {
                 return false;
             }

src/Workspaces/CSharp/Portable/Extensions/SyntaxTokenExtensions.cs

@@ -70,6 +70,13 @@ public static bool IsFirstTokenOnLine(this SyntaxToken token, SourceText text)
             return tokenLine > previousTokenLine;
         }
 
+        /// <summary>
+        /// Determines if there is preprocessor trivia *between* any of the <paramref name="tokens"/>
+        /// provided.  The <paramref name="tokens"/> will be deduped and then ordered by position.
+        /// Specifically, the first token will not have it's leading trivia checked, and the last
+        /// token will not have it's trailing trivia checked.  All other trivia will be checked to
+        /// see if it contains a preprocessor directive.
+        /// </summary>
         public static bool SpansPreprocessorDirective(this IEnumerable<SyntaxToken> tokens)
         {
             // we want to check all leading trivia of all tokens (except the 
@@ -79,7 +86,11 @@ public static bool SpansPreprocessorDirective(this IEnumerable<SyntaxToken> toke
             var first = true;
             var previousToken = default(SyntaxToken);
 
-            foreach (var token in tokens)
+            // Allow duplicate nodes/tokens to be passed in.  Also, allow the nodes/tokens
+            // to not be in any particular order when passed in.
+            var orderedTokens = tokens.Distinct().OrderBy(t => t.SpanStart);
+
+            foreach (var token in orderedTokens)
             {
                 if (first)
                 {
@@ -103,9 +114,7 @@ public static bool SpansPreprocessorDirective(this IEnumerable<SyntaxToken> toke
         }
 
         private static bool SpansPreprocessorDirective(SyntaxTriviaList list)
-        {
-            return list.Any(t => t.GetStructure() is DirectiveTriviaSyntax);
-        }
+            => list.Any(t => t.GetStructure() is DirectiveTriviaSyntax);
 
         /// <summary>
         /// Retrieves all trivia after this token, including it's trailing trivia and

src/Workspaces/Core/Portable/LanguageServices/SyntaxFactsService/ISyntaxFactsServiceExtensions.cs

 // 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.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -119,6 +120,9 @@ private static bool IsWordOrNumber(this ISyntaxFactsService syntaxFacts, SyntaxT
         public static bool SpansPreprocessorDirective(this ISyntaxFactsService service, SyntaxNode node)
             => service.SpansPreprocessorDirective(SpecializedCollections.SingletonEnumerable(node));
 
+        public static bool SpansPreprocessorDirective(this ISyntaxFactsService service, params SyntaxNode[] nodes)
+            => service.SpansPreprocessorDirective(nodes);
+
         public static bool IsWhitespaceOrEndOfLineTrivia(this ISyntaxFactsService syntaxFacts, SyntaxTrivia trivia)
             => syntaxFacts.IsWhitespaceTrivia(trivia) || syntaxFacts.IsEndOfLineTrivia(trivia);