Improve logic to find target symbol locations

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/UnsupportedCSharpLanguageVersionAnalyzer.cs

@@ -4,7 +4,6 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.Linq;
 using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -76,7 +75,7 @@ public sealed class UnsupportedCSharpLanguageVersionAnalyzer : DiagnosticAnalyze
                         typeSymbols.TryGetValue(attributeName, out INamedTypeSymbol? attributeSymbol) &&
                         SymbolEqualityComparer.Default.Equals(attributeClass, attributeSymbol))
                     {
-                        context.ReportDiagnostic(Diagnostic.Create(UnsupportedCSharpLanguageVersionError, context.Symbol.Locations.FirstOrDefault()));
+                        context.ReportDiagnostic(Diagnostic.Create(UnsupportedCSharpLanguageVersionError, context.Symbol.GetLocationFromAttributeDataOrDefault(attribute)));
 
                         // If we created a diagnostic for this symbol, we can stop. Even if there's multiple attributes, no need for repeated errors
                         return;

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/WinRTClassUsingNotifyPropertyChangedAttributesAnalyzer.cs

@@ -4,7 +4,6 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.Linq;
 using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -79,7 +78,7 @@ public sealed class WinRTClassUsingNotifyPropertyChangedAttributesAnalyzer : Dia
                     {
                         context.ReportDiagnostic(Diagnostic.Create(
                             GeneratorAttributeNamesToDiagnosticsMap[attributeClass.Name],
-                            context.Symbol.Locations.FirstOrDefault(),
+                            context.Symbol.GetLocationFromAttributeDataOrDefault(attribute),
                             context.Symbol));
                     }
                 }

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/WinRTGeneratedBindableCustomPropertyWithBasesMemberAnalyzer.cs

@@ -6,7 +6,6 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.Linq;
 using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -56,7 +55,7 @@ public sealed class WinRTGeneratedBindableCustomPropertyWithBasesMemberAnalyzer
                 }
 
                 // We only care about it if it's using [GeneratedBindableCustomProperty]
-                if (!typeSymbol.HasAttributeWithType(generatedBindableCustomPropertySymbol))
+                if (!typeSymbol.TryGetAttributeWithType(generatedBindableCustomPropertySymbol, out AttributeData? generatedBindableCustomPropertyAttribute))
                 {
                     return;
                 }
@@ -66,7 +65,7 @@ public sealed class WinRTGeneratedBindableCustomPropertyWithBasesMemberAnalyzer
                 {
                     context.ReportDiagnostic(Diagnostic.Create(
                         WinRTGeneratedBindableCustomPropertyWithBaseObservablePropertyOnField,
-                        typeSymbol.Locations.FirstOrDefault(),
+                        typeSymbol.GetLocationFromAttributeDataOrDefault(generatedBindableCustomPropertyAttribute),
                         typeSymbol,
                         fieldSymbol.ContainingType,
                         fieldSymbol.Name));
@@ -77,7 +76,7 @@ public sealed class WinRTGeneratedBindableCustomPropertyWithBasesMemberAnalyzer
                 {
                     context.ReportDiagnostic(Diagnostic.Create(
                         WinRTGeneratedBindableCustomPropertyWithBaseRelayCommand,
-                        typeSymbol.Locations.FirstOrDefault(),
+                        typeSymbol.GetLocationFromAttributeDataOrDefault(generatedBindableCustomPropertyAttribute),
                         typeSymbol,
                         methodSymbol));
                 }

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/WinRTRelayCommandIsNotGeneratedBindableCustomPropertyCompatibleAnalyzer.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
-using System.Linq;
 using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -50,7 +49,7 @@ public sealed class WinRTRelayCommandIsNotGeneratedBindableCustomPropertyCompati
                 }
 
                 // If the method is not using [RelayCommand], we can skip it
-                if (!methodSymbol.HasAttributeWithType(relayCommandSymbol))
+                if (!methodSymbol.TryGetAttributeWithType(relayCommandSymbol, out AttributeData? relayCommandAttribute))
                 {
                     return;
                 }
@@ -60,7 +59,7 @@ public sealed class WinRTRelayCommandIsNotGeneratedBindableCustomPropertyCompati
                 {
                     context.ReportDiagnostic(Diagnostic.Create(
                         WinRTRelayCommandIsNotGeneratedBindableCustomPropertyCompatible,
-                        methodSymbol.Locations.FirstOrDefault(),
+                        methodSymbol.GetLocationFromAttributeDataOrDefault(relayCommandAttribute),
                         methodSymbol));
                 }
             }, SymbolKind.Method);

src/CommunityToolkit.Mvvm.SourceGenerators/Extensions/ISymbolExtensions.cs

@@ -175,4 +175,31 @@ internal static class ISymbolExtensions
             accessibility == Accessibility.Public ||
             accessibility == Accessibility.Internal && symbol.ContainingAssembly.GivesAccessTo(assembly);
     }
+
+    /// <summary>
+    /// Gets the location of a given symbol that is in the same syntax tree of a specified attribute, or the first one.
+    /// </summary>
+    /// <param name="symbol">The input <see cref="ISymbol"/> instance to check.</param>
+    /// <param name="attributeData">The target <see cref="AttributeData"/> instance.</param>
+    /// <returns>The best <see cref="Location"/> match.</returns>
+    public static Location? GetLocationFromAttributeDataOrDefault(this ISymbol symbol, AttributeData attributeData)
+    {
+        Location? firstLocation = null;
+
+        // Get the syntax tree where the attribute application is located. We use
+        // it to try to find the symbol location that belongs to the same file.
+        SyntaxTree? attributeTree = attributeData.ApplicationSyntaxReference?.SyntaxTree;
+
+        foreach (Location location in symbol.Locations)
+        {
+            if (location.SourceTree == attributeTree)
+            {
+                return location;
+            }
+
+            firstLocation ??= location;
+        }
+
+        return firstLocation;
+    }
 }