Support generic interface methods (#251)

* improve diagnostic messages and prevent fatal errors from crashing the compiler.

* fix top level exception catching.

* spelling fix

* change wording of invalidSwizzleExpr diagnostic

* add speculative GenericsApp expr parsing

* add new test case of cascading generics call.

* Fixing bugs in compiling cascaded generic function calls.

Add implementation of DeclaredSubTypeWitness::SubstituteImpl()

This is not needed by the type checker, but needed by IR specialization. When input source contains cascading generic function call, the arguments to `specialize` instruction is currently represented as a substitution. The arg values of this subsittution can be a `DeclaredSubTypeWitness` when a generic function uses one of its generic parameter to specialize another generic function. When the top level generics function is being specialized, this substitution argument, which is a `DeclaredSubTypeWitness`, needs to be substituted with the witness that used to specialize the top level function in the specialized specialize instruction as well.

* add a test case for cascading generic function call.

* parser bug fix

* fixes #255

* add test case for issue #255

* Generate missing `specialize` instruction when calling a generic method from an interface constraint.

When calling a generic method via an interface, we should be generating the following ir:
...
f = lookup_interface_method(...)
f_s = specailize(f, declRef)
...

This commit fixes this  `emitFuncRef` function to emit the needed `specialize` instruction.

* fixes #260

This fix follows the second apporach in the disucssion. It generated mangled name for specialized functions by appending new substitution type names to the original mangled name.

* Disabling removing and re-inserting specailized functions in getSpecalizeFunc()

I am not sure why it is needed, it seems HLSL and GLSL backends are generating forward declarations anyways, so the order of functions in IRModule shouldn't matter.

* cleanup and complete test cases.

* fix warnings

1 files changed, 71 insertions, 33 deletions

diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index 595d58d7e..eb02d98c5 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -77,7 +77,7 @@ namespace Slang
             , sink(sink)
             , outerScope(outerScope)
         {}
-
+        Parser(const Parser & other) = default;
         Session* getSession()
         {
             return translationUnit->compileRequest->mSession;
@@ -1396,6 +1396,69 @@ namespace Slang
         return genericApp;
     }
 
+    static bool isGenericName(Parser* parser, Name* name)
+    {
+        auto lookupResult = lookUp(
+            parser->getSession(),
+            nullptr, // no semantics visitor available yet
+            name,
+            parser->currentScope);
+        if (!lookupResult.isValid() || lookupResult.isOverloaded())
+            return false;
+
+        auto decl = lookupResult.item.declRef.getDecl();
+        if (auto genericDecl = dynamic_cast<GenericDecl*>(decl))
+        {
+            return true;
+        }
+        else
+        {
+            return false;
+        }
+    }
+
+    static RefPtr<Expr> tryParseGenericApp(
+        Parser*                         parser,
+        RefPtr<Expr>    base)
+    {
+        Name * baseName = nullptr;
+        if (auto varExpr = base->As<VarExpr>())
+            baseName = varExpr->name;
+        // if base is a known generics, parse as generics
+        if (baseName && isGenericName(parser, baseName))
+            return parseGenericApp(parser, base);
+
+        // otherwise, we speculate as generics, and fallback to comparison when parsing failed
+        TokenSpan tokenSpan;
+        tokenSpan.mBegin = parser->tokenReader.mCursor;
+        tokenSpan.mEnd = parser->tokenReader.mEnd;
+        DiagnosticSink newSink;
+        newSink.sourceManager = parser->sink->sourceManager;
+        Parser newParser(*parser);
+        newParser.sink = &newSink;
+        auto speculateParseRs = parseGenericApp(&newParser, base);
+        if (newSink.errorCount == 0)
+        {
+            // disambiguate based on FOLLOW set
+            switch (peekTokenType(&newParser))
+            {
+            case TokenType::Dot:
+            case TokenType::LParent:
+            case TokenType::RParent:
+            case TokenType::RBracket:
+            case TokenType::Colon:
+            case TokenType::Comma:
+            case TokenType::QuestionMark:
+            case TokenType::Semicolon:
+            case TokenType::OpEql:
+            case TokenType::OpNeq:
+            {
+                return parseGenericApp(parser, base);
+            }
+            }
+        }
+        return base;
+    }
     static RefPtr<Expr> parseMemberType(Parser * parser, RefPtr<Expr> base)
     {
         RefPtr<MemberExpr> memberExpr = new MemberExpr();
@@ -2624,28 +2687,6 @@ namespace Slang
         return stmt;
     }
 
-    static bool isGenericName(Parser* parser, Name* name)
-    {
-        auto lookupResult = lookUp(
-            parser->getSession(),
-            nullptr, // no semantics visitor available yet
-            name,
-            parser->currentScope);
-        if(!lookupResult.isValid() || lookupResult.isOverloaded())
-            return false;
-
-        auto decl = lookupResult.item.declRef.getDecl();
-        if( auto genericDecl = dynamic_cast<GenericDecl*>(decl) )
-        {
-            return true;
-        }
-        else
-        {
-            return false;
-        }
-    }
-
-
     static bool isTypeName(Parser* parser, Name* name)
     {
         auto lookupResult = lookUp(
@@ -3367,24 +3408,18 @@ namespace Slang
         }
 #endif
     }
-
+    
     // We *might* be looking at an application of a generic to arguments,
     // but we need to disambiguate to make sure.
     static RefPtr<Expr> maybeParseGenericApp(
         Parser*                             parser,
 
         // TODO: need to support more general expressions here
-        RefPtr<VarExpr>     base)
+        RefPtr<Expr>     base)
     {
         if(peekTokenType(parser) != TokenType::OpLess)
             return base;
-
-        if(!isGenericName(parser, base->name))
-            return base;
-
-        // Okay, seems likely that we are looking at a generic app
-
-        return parseGenericApp(parser, base);
+        return tryParseGenericApp(parser, base);
     }
 
     static RefPtr<Expr> parsePrefixExpr(Parser* parser);
@@ -3769,7 +3804,10 @@ namespace Slang
                     parser->ReadToken(TokenType::Dot); 
                     memberExpr->name = expectIdentifier(parser).name;
 
-                    expr = memberExpr;
+                    if (peekTokenType(parser) == TokenType::OpLess)
+                        expr = maybeParseGenericApp(parser, memberExpr);
+                    else
+                        expr = memberExpr;
                 }
                 break;
             }