Fix RCS1176 (#1140)

Author: josefpihrt

ChangeLog.md

@@ -31,7 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix [RCS1154](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1154) ([#1105](https://github.com/JosefPihrt/Roslynator/pull/1105)).
 - Fix [RCS1211](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1211) ([#1095](https://github.com/JosefPihrt/Roslynator/pull/1095)).
 - Fix [RCS0005](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS0005) ([#1114](https://github.com/JosefPihrt/Roslynator/pull/1114)).
-- Fix [RCS1176](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1176.md) ([#1122](https://github.com/JosefPihrt/Roslynator/pull/1122)).
+- Fix [RCS1176](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1176.md) ([#1122](https://github.com/JosefPihrt/Roslynator/pull/1122), [#1140](https://github.com/JosefPihrt/Roslynator/pull/1140)).
 - Fix [RCS1085](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1085.md) ([#1120](https://github.com/josefpihrt/roslynator/pull/1120)).
 - Fix [RCS1208](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1208.md) ([#1119](https://github.com/JosefPihrt/Roslynator/pull/1119)).
 - [CLI] Fix member full declaration in generated documentation (command `generate-doc`) ([#1130](https://github.com/josefpihrt/roslynator/pull/1130)).

src/CSharp/CSharp/CSharpTypeAnalysis.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Josef Pihrt and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Threading;
 using Microsoft.CodeAnalysis;
@@ -502,7 +503,68 @@ public static bool IsExplicitThatCanBeImplicit(
         if (typeSymbol.IsKind(SymbolKind.ErrorType, SymbolKind.DynamicType))
             return false;
 
+        if (declarationExpression.Parent is ArgumentSyntax argument)
+            return AnalyzeArgument(argument, semanticModel, cancellationToken);
+
         return true;
+
+        static bool AnalyzeArgument(ArgumentSyntax argument, SemanticModel semanticModel, CancellationToken cancellationToken)
+        {
+            IParameterSymbol parameterSymbol = semanticModel.DetermineParameter(argument, cancellationToken: cancellationToken);
+
+            if (parameterSymbol is null)
+                return false;
+
+            if (SymbolEqualityComparer.Default.Equals(parameterSymbol.Type, parameterSymbol.OriginalDefinition.Type))
+                return true;
+
+            if (parameterSymbol.ContainingSymbol is IMethodSymbol methodSymbol)
+            {
+                ImmutableArray<ITypeSymbol> typeParameterList = methodSymbol.TypeArguments;
+
+                ITypeParameterSymbol typeParameterSymbol = null;
+                for (int i = 0; i < typeParameterList.Length; i++)
+                {
+                    if (SymbolEqualityComparer.Default.Equals(typeParameterList[i], parameterSymbol.Type))
+                    {
+                        typeParameterSymbol = methodSymbol.TypeParameters[i];
+                        break;
+                    }
+                }
+
+                if (typeParameterSymbol is not null
+                    && argument.Parent is ArgumentListSyntax argumentList
+                    && argumentList.Parent is InvocationExpressionSyntax invocation)
+                {
+                    switch (invocation.Expression.Kind())
+                    {
+                        case SyntaxKind.IdentifierName:
+                            return false;
+
+                        case SyntaxKind.GenericName:
+                            return true;
+
+                        case SyntaxKind.SimpleMemberAccessExpression:
+                            var memberAccess = (MemberAccessExpressionSyntax)invocation.Expression;
+
+                            if (memberAccess.Name.IsKind(SyntaxKind.IdentifierName))
+                                return false;
+
+                            if (memberAccess.Name.IsKind(SyntaxKind.GenericName))
+                                return true;
+
+                            Debug.Fail(memberAccess.Name.Kind().ToString());
+                            break;
+
+                        default:
+                            Debug.Fail(invocation.Expression.Kind().ToString());
+                            break;
+                    }
+                }
+            }
+
+            return false;
+        }
     }
 
     public static bool IsExplicitThatCanBeImplicit(

src/Tests/Analyzers.Tests/RCS1176UseVarInsteadOfExplicitTypeWhenTypeIsNotObviousTests.cs

@@ -116,6 +116,46 @@ void M()
 ");
     }
 
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseVarInsteadOfExplicitTypeWhenTypeIsNotObvious)]
+    public async Task Test_TryParse_GenericType()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using System;
+#nullable enable
+
+class C
+{
+    void M()
+    {
+        bool TryParse<T>(string? s, out T t)
+        {
+            t = default!;
+            return false;
+        }
+
+        TryParse<IntPtr>(""wasted"", out [|IntPtr|] i);
+    }
+}
+", @"
+using System;
+#nullable enable
+
+class C
+{
+    void M()
+    {
+        bool TryParse<T>(string? s, out T t)
+        {
+            t = default!;
+            return false;
+        }
+
+        TryParse<IntPtr>(""wasted"", out var i);
+    }
+}
+");
+    }
+
     [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseVarInsteadOfExplicitTypeWhenTypeIsNotObvious)]
     public async Task TestNoDiagnostic_ForEach_DeclarationExpression()
     {
@@ -237,6 +277,53 @@ void M()
         Type? nullableType = type;
     }
 }
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseVarInsteadOfExplicitTypeWhenTypeIsNotObvious)]
+    public async Task TestNoDiagnostic_InferredType_Invocation_IdentifierName()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+#nullable enable
+
+class C
+{
+    void M()
+    {
+        bool TryParse<T>(string? s, out T t)
+        {
+            t = default!;
+            return false;
+        }
+
+        TryParse(""wasted"", out IntPtr i);
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseVarInsteadOfExplicitTypeWhenTypeIsNotObvious)]
+    public async Task TestNoDiagnostic_InferredType_Invocation_MemberAccessExpression()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+#nullable enable
+
+static class C
+{
+    static void M()
+    {
+
+        C.TryParse(""wasted"", out IntPtr i);
+    }
+
+    static bool TryParse<T>(string? s, out T t)
+    {
+        t = default!;
+        return false;
+    }
+}
 ");
     }
 }