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dotnet · Mar 5, 2018 · b13c65c · b13c65c
1 parent d0bb51d
commit b13c65c
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Showing 3 changed files with 12 additions and 10 deletions.
diff --git a/src/Compilers/CSharp/Portable/CodeGen/EmitConversion.cs b/src/Compilers/CSharp/Portable/CodeGen/EmitConversion.cs
@@ -48,18 +48,21 @@ private void EmitConversionExpression(BoundConversion conversion, bool used)
 
         private void EmitSpecialUserDefinedConversion(BoundConversion conversion, bool used, BoundExpression operand)
         {
-            var typeTo = conversion.Type;
+            var typeTo = (NamedTypeSymbol)conversion.Type;
 
             Debug.Assert((operand.Type.IsArray()) &&
                          this._module.Compilation.IsReadOnlySpanType(typeTo),
-                         "only special kinds of conversions involvling ReadOnlySpan may be handled in emit");
+                         "only special kinds of conversions involving ReadOnlySpan may be handled in emit");
 
-            if (!TryEmitReadonlySpanAsBlobWrapper((NamedTypeSymbol)typeTo, operand, used, inPlace: false))
+            if (!TryEmitReadonlySpanAsBlobWrapper(typeTo, operand, used, inPlace: false))
             {
+                // there are several reasons that could prevent us from emitting a wrapper
+                // in such case we just emit the operand and then invoke the conversion method 
                 EmitExpression(operand, used);
                 if (used)
                 {
-                    _builder.EmitOpCode(ILOpCode.Call, 0);
+                    // consumes 1 argument (array) and produces one result (span)
+                    _builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0);
                     EmitSymbolToken(conversion.SymbolOpt, conversion.Syntax, optArgList: null);
                 }
             }

diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs
@@ -1016,10 +1016,9 @@ private BoundExpression RewriteUserDefinedConversion(
 
             // do not rewrite user defined conversion 
             // - in expression trees or 
-            // - special situations when converting to ReadOnlySpan, which has special support in codegen
-            var doNotLowerToCall = _inExpressionLambda ||
-                                   (rewrittenOperand.Type.IsArray()) &&
-                                   _compilation.IsReadOnlySpanType(rewrittenType);
+            // - special situations when converting from array to ReadOnlySpan, which has special support in codegen
+            bool doNotLowerToCall = _inExpressionLambda ||
+                                    (rewrittenOperand.Type.IsArray()) && _compilation.IsReadOnlySpanType(rewrittenType);
 
             BoundExpression result =
                 doNotLowerToCall

diff --git a/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs b/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs
@@ -1343,9 +1343,9 @@ public ref readonly T Current
                 }
             }
 
-            public static implicit operator ReadOnlySpan<T>(T[] array) => array == null? default: new ReadOnlySpan<T>(array);
+            public static implicit operator ReadOnlySpan<T>(T[] array) => array == null ? default : new ReadOnlySpan<T>(array);
 
-            public static implicit operator ReadOnlySpan<T>(string stringValue) => string.IsNullOrEmpty(stringValue)? default: new ReadOnlySpan<T>((T[])(object)stringValue.ToCharArray());
+            public static implicit operator ReadOnlySpan<T>(string stringValue) => string.IsNullOrEmpty(stringValue) ? default : new ReadOnlySpan<T>((T[])(object)stringValue.ToCharArray());
         }
 
         public readonly ref struct SpanLike<T>