Fix for #7840: add missing check for DynamicAttribute type

src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs

@@ -2879,6 +2879,17 @@ internal bool HasDynamicEmitAttributes()
                 (object)GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_DynamicAttribute__ctorTransformFlags) != null;
         }
 
+        /// <summary>
+        /// Returns whether the compilation has the Boolean type and if it's good.
+        /// </summary>
+        /// <returns>Returns true if Boolean is present and healthy.</returns>
+        internal bool CanEmitBoolean()
+        {
+            var boolType = GetSpecialType(SpecialType.System_Boolean);
+            var diagnostic = boolType.GetUseSiteDiagnostic();
+            return (diagnostic == null) || (diagnostic.Severity != DiagnosticSeverity.Error);
+        }
+
         internal override AnalyzerDriver AnalyzerForLanguage(ImmutableArray<DiagnosticAnalyzer> analyzers, AnalyzerManager analyzerManager)
         {
             Func<SyntaxNode, SyntaxKind> getKind = node => node.Kind();

src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedFieldSymbolBase.cs

@@ -45,14 +45,11 @@ internal override void AddSynthesizedAttributes(ModuleCompilationState compilati
 
             CSharpCompilation compilation = this.DeclaringCompilation;
 
-            // Assume that someone checked earlier that the attribute ctor is available and has no use-site errors.
             AddSynthesizedAttribute(ref attributes, compilation.TrySynthesizeAttribute(WellKnownMember.System_Runtime_CompilerServices_CompilerGeneratedAttribute__ctor));
 
-            // TODO (tomat): do we need to emit dynamic attribute on any synthesized field?
-            if (this.Type.ContainsDynamic())
+            if (this.Type.ContainsDynamic() && compilation.HasDynamicEmitAttributes() && compilation.CanEmitBoolean())
             {
-                // Assume that someone checked earlier that the attribute ctor is available and has no use-site errors.
-                AddSynthesizedAttribute(ref attributes, compilation.SynthesizeDynamicAttribute(this.Type, customModifiersCount: 0));
+                AddSynthesizedAttribute(ref attributes, compilation.SynthesizeDynamicAttribute(this.Type, this.CustomModifiers.Length));
             }
         }
 

src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedImplementationMethod.cs

@@ -81,9 +81,9 @@ internal override void AddSynthesizedAttributes(ModuleCompilationState compilati
         {
             base.AddSynthesizedAttributes(compilationState, ref attributes);
 
-            if (this.ReturnType.ContainsDynamic())
+            var compilation = this.DeclaringCompilation;
+            if (this.ReturnType.ContainsDynamic() && compilation.HasDynamicEmitAttributes() && compilation.CanEmitBoolean())
             {
-                var compilation = this.DeclaringCompilation;
                 AddSynthesizedAttribute(ref attributes, compilation.SynthesizeDynamicAttribute(this.ReturnType, this.ReturnTypeCustomModifiers.Length));
             }
         }

src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedParameterSymbol.cs

@@ -159,14 +159,9 @@ internal override void AddSynthesizedAttributes(ModuleCompilationState compilati
             // this is a no-op.  Emitting an error here, or when the original parameter was bound, would
             // adversely effect the compilation or potentially change overload resolution.  
             var compilation = this.DeclaringCompilation;
-            if (Type.ContainsDynamic() && compilation.HasDynamicEmitAttributes())
+            if (Type.ContainsDynamic() && compilation.HasDynamicEmitAttributes() && compilation.CanEmitBoolean())
             {
-                var boolType = compilation.GetSpecialType(SpecialType.System_Boolean);
-                var diagnostic = boolType.GetUseSiteDiagnostic();
-                if ((diagnostic == null) || (diagnostic.Severity != DiagnosticSeverity.Error))
-                {
-                    AddSynthesizedAttribute(ref attributes, compilation.SynthesizeDynamicAttribute(this.Type, this.CustomModifiers.Length, this.RefKind));
-                }
+                AddSynthesizedAttribute(ref attributes, compilation.SynthesizeDynamicAttribute(this.Type, this.CustomModifiers.Length, this.RefKind));
             }
         }