Update code to use GetFirstLocation() instead of Locations[0] or Locations.First() (#80709)

Author: CyrusNajmabadi

src/Compilers/CSharp/Portable/Symbols/Source/ExtensionGroupingInfo.cs

@@ -474,7 +474,7 @@ static void checkCollisions(IEnumerable<SourceNamedTypeSymbol> extensions, Func<
                         alreadyReportedExtensions ??= PooledHashSet<SourceNamedTypeSymbol>.GetInstance();
                         if (alreadyReportedExtensions.Add(extension))
                         {
-                            diagnostics.Add(ErrorCode.ERR_ExtensionBlockCollision, extension.Locations[0]);
+                            diagnostics.Add(ErrorCode.ERR_ExtensionBlockCollision, extension.GetFirstLocation());
                         }
                     }
                 }

src/Compilers/Core/Portable/Emit/EditAndContinue/DefinitionMap.cs

@@ -353,7 +353,7 @@ protected abstract void GetStateMachineFieldMapFromMetadata(
                 {
                     diagnostics.Add(MessageProvider.CreateDiagnostic(
                         MessageProvider.ERR_InvalidDebugInfo,
-                        method.Locations.First(),
+                        method.GetFirstLocation(),
                         method,
                         MetadataTokens.GetToken(methodHandle),
                         method.ContainingAssembly,
@@ -438,7 +438,7 @@ protected abstract void GetStateMachineFieldMapFromMetadata(
                     {
                         diagnostics.Add(MessageProvider.CreateDiagnostic(
                             MessageProvider.ERR_InvalidDebugInfo,
-                            method.Locations.First(),
+                            method.GetFirstLocation(),
                             method,
                             MetadataTokens.GetToken(localSignature),
                             method.ContainingAssembly,
@@ -479,7 +479,7 @@ private void ReportMissingStateMachineAttribute(DiagnosticBag diagnostics, IMeth
         {
             diagnostics.Add(MessageProvider.CreateDiagnostic(
                 MessageProvider.ERR_EncUpdateFailedMissingSymbol,
-                method.Locations.First(),
+                method.GetFirstLocation(),
                 CodeAnalysisResources.Attribute,
                 stateMachineAttributeFullName));
         }

src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs

@@ -1453,7 +1453,7 @@ private static Location GetNamedEntityLocation(INamedEntity errorEntity)
 
         protected static Location GetSymbolLocation(ISymbolInternal symbolOpt)
         {
-            return symbolOpt != null && !symbolOpt.Locations.IsDefaultOrEmpty ? symbolOpt.Locations[0] : Location.None;
+            return symbolOpt?.GetFirstLocationOrNone() ?? Location.None;
         }
 
         internal TypeAttributes GetTypeAttributes(ITypeDefinition typeDef)

src/Compilers/Core/Portable/Symbols/ISymbolInternal.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Immutable;
 using System.Reflection.Metadata;
 using System.Threading;
@@ -89,6 +90,21 @@ internal interface ISymbolInternal
         /// </summary>
         bool IsDefinition { get; }
 
+        /// <summary>
+        /// Similar to getting the first location from <see cref="Locations"/>.  However, this can be more efficient as
+        /// an intermediary array may not need to be created.  This can often be advantageous for perf as most symbols
+        /// only have a single location, and most clients only need the first location for some purpose (like error
+        /// reporting).
+        /// </summary>
+        /// <exception cref="InvalidOperationException">If the symbol has no locations.</exception>
+        Location GetFirstLocation();
+
+        /// <summary>
+        /// Equivalent to calling <see cref="GetFirstLocation"/>,  except that if <see cref="Locations"/> is empty this
+        /// will return <see cref="Location.None"/>.
+        /// </summary>
+        Location GetFirstLocationOrNone();
+
         /// <summary>
         /// Gets the locations where the symbol was originally defined, either in source or
         /// metadata. Some symbols (for example, partial classes) may be defined in more than one

src/Compilers/VisualBasic/Portable/Analysis/FlowAnalysis/DataFlowPass.vb

@@ -197,10 +197,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             If Not local.IsFunctionValue AndAlso Not String.IsNullOrEmpty(local.Name) Then
                 If _writtenVariables.Contains(local) Then
                     If local.IsConst Then
-                        Me.diagnostics.Add(ERRID.WRN_UnusedLocalConst, local.Locations(0), If(local.Name, "dummy"))
+                        Me.diagnostics.Add(ERRID.WRN_UnusedLocalConst, local.GetFirstLocation(), If(local.Name, "dummy"))
                     End If
                 Else
-                    Me.diagnostics.Add(ERRID.WRN_UnusedLocal, local.Locations(0), If(local.Name, "dummy"))
+                    Me.diagnostics.Add(ERRID.WRN_UnusedLocal, local.GetFirstLocation(), If(local.Name, "dummy"))
                 End If
             End If
         End Sub

src/Compilers/VisualBasic/Portable/Binding/Binder_Conversions.vb

@@ -1569,7 +1569,7 @@ DoneWithDiagnostics:
                 If delegateParam.IsByRef OrElse delegateParam.OriginalDefinition.Type.IsTypeParameter() Then
                     Dim restrictedType As TypeSymbol = Nothing
                     If delegateParam.Type.IsRestrictedTypeOrArrayType(restrictedType) Then
-                        ReportDiagnostic(diagnostics, lambda.LambdaSymbol.Parameters(delegateParam.Ordinal).Locations(0),
+                        ReportDiagnostic(diagnostics, lambda.LambdaSymbol.Parameters(delegateParam.Ordinal).GetFirstLocation(),
                                          ERRID.ERR_RestrictedType1, restrictedType)
                     End If
                 End If

src/Compilers/VisualBasic/Portable/Binding/Binder_Lambda.vb

@@ -117,7 +117,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                                                                unboundType,
                                                                unboundParam.IsByRef,
                                                                unboundParam.Syntax,
-                                                               unboundParam.Locations(0))
+                                                               unboundParam.GetFirstLocation())
             Next
 
             If parameters.Length <> targetSignature.ParameterTypes.Length Then
@@ -142,7 +142,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                                                                    unboundType,
                                                                    unboundParam.IsByRef,
                                                                    unboundParam.Syntax,
-                                                                   unboundParam.Locations(0))
+                                                                   unboundParam.GetFirstLocation())
                 Next
             End If
 

src/Compilers/VisualBasic/Portable/Binding/ExecutableCodeBinder.vb

@@ -136,7 +136,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                         Dim bestLocation As Location = Nothing
                         For Each symbol In labels
                             Debug.Assert(symbol.Locations.Length = 1)
-                            Dim sourceLocation As Location = symbol.Locations(0)
+                            Dim sourceLocation As Location = symbol.GetFirstLocation()
                             If bestSymbol Is Nothing OrElse Me.Compilation.CompareSourceLocations(bestLocation, sourceLocation) > 0 Then
                                 bestSymbol = symbol
                                 bestLocation = sourceLocation

src/Compilers/VisualBasic/Portable/Compilation/ClsComplianceChecker.vb

@@ -763,7 +763,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                 If attributeData.IsTargetAttribute(AttributeDescription.CLSCompliantAttribute) Then
                     Dim attributeClass = attributeData.AttributeClass
                     If attributeClass IsNot Nothing Then
-                        _diagnostics.ReportUseSite(attributeClass, If(symbol.Locations.IsEmpty, NoLocation.Singleton, symbol.Locations(0)))
+                        _diagnostics.ReportUseSite(attributeClass, If(symbol.Locations.IsEmpty, NoLocation.Singleton, symbol.GetFirstLocation()))
                     End If
 
                     If Not attributeData.HasErrors Then
@@ -831,7 +831,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         End Function
 
         Private Sub AddDiagnostic(symbol As Symbol, code As ERRID, ParamArray args As Object())
-            Dim location = If(symbol.Locations.IsEmpty, NoLocation.Singleton, symbol.Locations(0))
+            Dim location = If(symbol.Locations.IsEmpty, NoLocation.Singleton, symbol.GetFirstLocation())
             Me.AddDiagnostic(symbol, code, location, args)
         End Sub
 

src/Compilers/VisualBasic/Portable/Compilation/DocumentationComments/DocumentationCommentCompiler.Includes.vb

@@ -664,7 +664,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                                         ' can be found by the name, just deterministically choose which one to use
                                         If symbolCommentId Is Nothing OrElse
                                                 Me._compilation.CompareSourceLocations(
-                                                    smallestSymbol.Locations(0), symbol.Locations(0)) > 0 Then
+                                                    smallestSymbol.GetFirstLocation(), symbol.GetFirstLocation()) > 0 Then
 
                                             symbolCommentId = id
                                             smallestSymbol = symbol