From 817603e87350f96b2cf1fd57158fe59da8de4be3 Mon Sep 17 00:00:00 2001
From: Andy Gocke <angocke@microsoft.com>
Date: Fri, 17 Jan 2020 14:50:31 -0800
Subject: [PATCH] Remove capturing lambda from binding hot path (#41055)

Capturing lambdas should be avoided in core compiler code
as they generate excess allocations

Fixes #41054
---
 .../Portable/Binder/Binder_Expressions.cs     | 25 ++++++++++++-------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
index ce1bc9413ca..fdd8adeffd4 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
@@ -274,15 +274,22 @@ internal BoundExpression BindToNaturalType(BoundExpression expression, Diagnosti
                     }
                     break;
                 case BoundTupleLiteral sourceTuple:
-                    result = new BoundConvertedTupleLiteral(
-                        sourceTuple.Syntax,
-                        sourceTuple,
-                        wasTargetTyped: false,
-                        sourceTuple.Arguments.SelectAsArray(e => BindToNaturalType(e, diagnostics, reportDefaultMissingType)),
-                        sourceTuple.ArgumentNamesOpt,
-                        sourceTuple.InferredNamesOpt,
-                        sourceTuple.Type, // same type to keep original element names
-                        sourceTuple.HasErrors).WithSuppression(sourceTuple.IsSuppressed);
+                    {
+                        var boundArgs = ArrayBuilder<BoundExpression>.GetInstance(sourceTuple.Arguments.Length);
+                        foreach (var arg in sourceTuple.Arguments)
+                        {
+                            boundArgs.Add(BindToNaturalType(arg, diagnostics, reportDefaultMissingType));
+                        }
+                        result = new BoundConvertedTupleLiteral(
+                            sourceTuple.Syntax,
+                            sourceTuple,
+                            wasTargetTyped: false,
+                            boundArgs.ToImmutableAndFree(),
+                            sourceTuple.ArgumentNamesOpt,
+                            sourceTuple.InferredNamesOpt,
+                            sourceTuple.Type, // same type to keep original element names
+                            sourceTuple.HasErrors).WithSuppression(sourceTuple.IsSuppressed);
+                    }
                     break;
                 case BoundDefaultLiteral defaultExpr:
                     {
-- 
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