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, 18 insertions, 0 deletions

diff --git a/source/slang/mangle.cpp b/source/slang/mangle.cpp
index dca48f671..38c2b29a8 100644
--- a/source/slang/mangle.cpp
+++ b/source/slang/mangle.cpp
@@ -350,6 +350,24 @@ namespace Slang
             DeclRef<Decl>(declRef.decl, declRef.substitutions));
     }
 
+    String mangleSpecializedFuncName(String baseName, RefPtr<Substitutions> subst)
+    {
+        ManglingContext context;
+        emitRaw(&context, baseName.Buffer());
+        emitRaw(&context, "_G");
+        while (subst)
+        {
+            if (auto genSubst = subst.As<GenericSubstitution>())
+            {
+                for (auto a : genSubst->args)
+                    emitVal(&context, a);
+                break;
+            }
+            subst = subst->outer;
+        }
+        return context.sb.ProduceString();
+    }
+
     String getMangledName(Decl* decl)
     {
         return getMangledName(makeDeclRef(decl));