Support `expand` on concrete tuple values. (#8106)

Closes #8061.

Along with the fix, also enhanced coercion/overload resolution to filter
candidates based on the target type, allowing
`tests\language-feature\higher-order-functions\overloaded.slang` to
pass.

1 files changed, 34 insertions, 27 deletions

diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 7f7c39929..7e9740b53 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -118,10 +118,6 @@ public:
 
     bool hasSeenCompletionToken = false;
 
-    // Track whether or not we are inside a generics that has variadic parameters.
-    // If so we will enable the new `expand` and `each` keyword.
-    bool isInVariadicGenerics = false;
-
     TokenReader tokenReader;
     DiagnosticSink* sink;
     SourceLoc lastErrorLoc;
@@ -1619,9 +1615,6 @@ static void ParseGenericDeclImpl(Parser* parser, GenericDecl* decl, const TFunc&
 {
     parser->ReadToken(TokenType::OpLess);
     parser->genericDepth++;
-    bool oldIsInVariadicGenerics = parser->isInVariadicGenerics;
-    SLANG_DEFER(parser->isInVariadicGenerics = oldIsInVariadicGenerics);
-
     for (;;)
     {
         const TokenType tokenType = parser->tokenReader.peekTokenType();
@@ -1635,11 +1628,6 @@ static void ParseGenericDeclImpl(Parser* parser, GenericDecl* decl, const TFunc&
         auto genericParam = ParseGenericParamDecl(parser, decl);
         AddMember(decl, genericParam);
 
-        if (as<GenericTypePackParamDecl>(genericParam))
-        {
-            parser->isInVariadicGenerics = true;
-        }
-
         // Make sure we make forward progress.
         if (parser->tokenReader.getCursor() == currentCursor)
             advanceToken(parser);
@@ -1869,7 +1857,6 @@ static Stmt* parseOptBody(Parser* parser)
     unparsedStmt->currentScope = parser->currentScope;
     unparsedStmt->outerScope = parser->outerScope;
     unparsedStmt->sourceLanguage = parser->getSourceLanguage();
-    unparsedStmt->isInVariadicGenerics = parser->isInVariadicGenerics;
     parser->FillPosition(unparsedStmt);
     List<Token>& tokens = unparsedStmt->tokens;
     int braceDepth = 0;
@@ -8616,6 +8603,32 @@ static Expr* parseEachExpr(Parser* parser, SourceLoc loc)
     return eachExpr;
 }
 
+// Check if a specific contextual keyword is available and not shadowed by user-defined decls.
+static bool isKeywordAvailable(Parser* parser, const char* keyword)
+{
+    if (!parser->semanticsVisitor || !parser->currentLookupScope)
+        return true;
+    if (lookUp(
+            parser->astBuilder,
+            parser->semanticsVisitor,
+            parser->semanticsVisitor->getName(keyword),
+            parser->currentLookupScope)
+            .isValid())
+        return false;
+    return true;
+}
+
+// Advance the token reader if the next token is a keyword and the keyword is not shadowed.
+static bool advanceIfAvailableKeyword(Parser* parser, const char* keyword)
+{
+    if (parser->LookAheadToken(keyword) && isKeywordAvailable(parser, keyword))
+    {
+        parser->ReadToken();
+        return true;
+    }
+    return false;
+}
+
 static Expr* parsePrefixExpr(Parser* parser)
 {
     auto tokenType = peekTokenType(parser);
@@ -8650,18 +8663,13 @@ static Expr* parsePrefixExpr(Parser* parser)
             {
                 return parseSPIRVAsmExpr(parser, tokenLoc);
             }
-            else if (parser->isInVariadicGenerics)
+            else if (advanceIfAvailableKeyword(parser, "expand"))
             {
-                // If we are inside a variadic generic, we also need to recognize
-                // the new `expand` and `each` keyword for dealing with variadic packs.
-                if (AdvanceIf(parser, "expand"))
-                {
-                    return parseExpandExpr(parser, tokenLoc);
-                }
-                else if (AdvanceIf(parser, "each"))
-                {
-                    return parseEachExpr(parser, tokenLoc);
-                }
+                return parseExpandExpr(parser, tokenLoc);
+            }
+            else if (advanceIfAvailableKeyword(parser, "each"))
+            {
+                return parseEachExpr(parser, tokenLoc);
             }
             return parsePostfixExpr(parser);
         }
@@ -8795,7 +8803,6 @@ Stmt* parseUnparsedStmt(
     SemanticsVisitor* semanticsVisitor,
     TranslationUnitRequest* translationUnit,
     SourceLanguage sourceLanguage,
-    bool isInVariadicGenerics,
     TokenSpan const& tokens,
     DiagnosticSink* sink,
     Scope* currentScope,
@@ -8819,7 +8826,6 @@ Stmt* parseUnparsedStmt(
     parser.semanticsVisitor = semanticsVisitor;
     parser.currentScope = parser.currentLookupScope = currentScope;
     parser.currentModule = semanticsVisitor->getShared()->getModule()->getModuleDecl();
-    parser.isInVariadicGenerics = isInVariadicGenerics;
     return parser.parseBlockStatement();
 }
 
@@ -9388,7 +9394,8 @@ static NodeBase* parseMagicTypeModifier(Parser* parser, void* /*userData*/)
     {
         modifier->magicNodeType = syntaxClass;
     }
-    // TODO: print diagnostic if the magic type name doesn't correspond to an actual ASTNodeType.
+    // TODO: print diagnostic if the magic type name doesn't correspond to an actual
+    // ASTNodeType.
     parser->ReadToken(TokenType::RParent);
 
     return modifier;