From 364e43264b9f69957ddaed8890392d82fb25c822 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Tue, 4 Oct 2022 15:21:17 -0700
Subject: Fix `ApplyExtensionToType` on own type being extended. (#2430)

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-check-decl.cpp | 10 +++++++++-
 source/slang/slang.natvis         |  7 ++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

(limited to 'source')

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index a7cd768b1..b18e1c4da 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -5226,9 +5226,17 @@ namespace Slang
             constraints.loc = extDecl->loc;
             constraints.genericDecl = extGenericDecl;
 
+            // Inside the body of an extension declaration, we may end up trying to apply that
+            // extension to its own target type.
+            // If we see that we are in that case, we can apply the extension declaration as - is,
+            // without any additional substitutions.
+            if (extDecl->targetType->equals(type))
+            {
+                return extDeclRef;
+            }
+
             if (!TryUnifyTypes(constraints, extDecl->targetType.Ptr(), type))
                 return DeclRef<ExtensionDecl>();
-
             auto constraintSubst = trySolveConstraintSystem(&constraints, DeclRef<Decl>(extGenericDecl, nullptr).as<GenericDecl>());
             if (!constraintSubst)
             {
diff --git a/source/slang/slang.natvis b/source/slang/slang.natvis
index 6c8f15ec9..ee868be62 100644
--- a/source/slang/slang.natvis
+++ b/source/slang/slang.natvis
@@ -282,6 +282,8 @@
         <DisplayString Condition="nameAndLoc.name!=0">{nameAndLoc.name->text}: {astNodeType}</DisplayString>
         <DisplayString Condition="nameAndLoc.name==0">{astNodeType}</DisplayString>
         <Expand>
+            <Item Name="[Name]" Condition="nameAndLoc.name!=0">nameAndLoc.name->text</Item>
+            <Item Name="[Parent]">parentDecl</Item>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::ContainerDecl">(Slang::ContainerDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::ExtensionDecl">(Slang::ExtensionDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::StructDecl">(Slang::StructDecl*)&amp;astNodeType</ExpandedItem>
@@ -322,6 +324,7 @@
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::EmptyDecl">(Slang::EmptyDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::SyntaxDecl">(Slang::SyntaxDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::DeclGroup">(Slang::DeclGroup*)&amp;astNodeType</ExpandedItem>
+            
             <Item Name="Decl">(Slang::DeclBase*)this,nd</Item>
         </Expand>
     </Type>
@@ -369,7 +372,7 @@
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::EmptyDecl">(Slang::EmptyDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::SyntaxDecl">(Slang::SyntaxDecl*)&amp;astNodeType</ExpandedItem>
             <ExpandedItem Condition="astNodeType == Slang::ASTNodeType::DeclGroup">(Slang::DeclGroup*)&amp;astNodeType</ExpandedItem>
-            <Item Name="Decl">(Slang::DeclBase*)this,nd</Item>
+            <Item Name="Decl">(Slang::Decl*)this,nd</Item>
         </Expand>
     </Type>
 
@@ -473,8 +476,6 @@
     <Type Name="Slang::AggTypeDecl">
         <DisplayString>{nameAndLoc.name}: {astNodeType}</DisplayString>
         <Expand>
-            <Item Name="[Name]">nameAndLoc.name</Item>
-            <Item Name="[Parent]">parentDecl</Item>
             <Item Name="[Members]">members</Item>
         </Expand>
     </Type>
-- 
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