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, 54 insertions, 6 deletions

diff --git a/source/slang/check.cpp b/source/slang/check.cpp
index 6bb7c232f..320b22bdb 100644
--- a/source/slang/check.cpp
+++ b/source/slang/check.cpp
@@ -1588,6 +1588,44 @@ namespace Slang
             return true;
         }
 
+        bool doesGenericSignatureMatchRequirement(
+            GenericDecl * genDecl,
+            DeclRef<GenericDecl> requirementGenDecl)
+        {
+            // TODO: genDecl should be a DeclRef to capture the environment generic variables needed to get 
+            // a concrete type for a generic constraint super type (e.g. when this member belongs to a generic type)
+
+            if (genDecl->Members.Count() != requirementGenDecl.getDecl()->Members.Count())
+                return false;
+            for (UInt i = 0; i < genDecl->Members.Count(); i++)
+            {
+                auto genMbr = genDecl->Members[i];
+                auto requiredGenMbr = genDecl->Members[i];
+                if (auto genTypeMbr = genMbr.As<GenericTypeParamDecl>())
+                {
+                    if (auto requiredGenTypeMbr = requiredGenMbr.As<GenericTypeParamDecl>())
+                    {
+                    }
+                    else
+                        return false;
+                }
+                else if (auto genTypeConstraintMbr = genMbr.As<GenericTypeConstraintDecl>())
+                {
+                    if (auto requiredTypeConstraintMbr = requiredGenMbr.As<GenericTypeConstraintDecl>())
+                    {
+                        if (!genTypeConstraintMbr->sup->Equals(requiredTypeConstraintMbr->sup))
+                        {
+                            return false;
+                        }
+                    }
+                    else
+                        return false;
+                }
+            }
+            return doesMemberSatisfyRequirement(genDecl->inner.Ptr(),
+                DeclRef<Decl>(requirementGenDecl.getDecl()->inner.Ptr(), requirementGenDecl.substitutions));
+        }
+
         // Does the given `memberDecl` work as an implementation
         // to satisfy the requirement `requiredMemberDeclRef`
         // from an interface?
@@ -1634,6 +1672,13 @@ namespace Slang
                         requiredInitDecl);
                 }
             }
+            else if (auto genDecl = dynamic_cast<GenericDecl*>(memberDecl))
+            {
+                if (auto requiredGenDeclRef = requiredMemberDeclRef.As<GenericDecl>())
+                {
+                    return doesGenericSignatureMatchRequirement(genDecl, requiredGenDeclRef);
+                }
+            }
             else if (auto subStructTypeDecl = dynamic_cast<AggTypeDecl*>(memberDecl))
             {
                 // this is a sub type (e.g. nested struct declaration) in an aggregate type
@@ -4462,9 +4507,13 @@ namespace Slang
 
             DeclRef<Decl> innerDeclRef(GetInner(baseGenericRef), subst);
 
+            RefPtr<Expr> base;
+            if (auto mbrExpr = baseExpr.As<MemberExpr>())
+                base = mbrExpr->BaseExpression;
+
             return ConstructDeclRefExpr(
                 innerDeclRef,
-                nullptr,
+                base,
                 originalExpr->loc);
         }
 
@@ -5738,7 +5787,6 @@ namespace Slang
             // declarations with the same name, so this becomes a specialized case of
             // overload resolution.
 
-
             // Start by checking the base expression and arguments.
             auto& baseExpr = genericAppExpr->FunctionExpr;
             baseExpr = CheckTerm(baseExpr);
@@ -6095,9 +6143,9 @@ namespace Slang
                 case 'w': case 'a': elementIndex = 3; break;
                 default:
                     // An invalid character in the swizzle is an error
-                    if (!isRewriteMode())
+                    if (!isRewriteMode() && !anyError)
                     {
-                        getSink()->diagnose(swizExpr, Diagnostics::unimplemented, "invalid component name for swizzle");
+                        getSink()->diagnose(swizExpr, Diagnostics::invalidSwizzleExpr, swizzleText, baseElementType->ToString());
                     }
                     anyError = true;
                     continue;
@@ -6109,9 +6157,9 @@ namespace Slang
                 // Make sure the index is in range for the source type
                 if (elementIndex >= limitElement)
                 {
-                    if (!isRewriteMode())
+                    if (!isRewriteMode() && !anyError)
                     {
-                        getSink()->diagnose(swizExpr, Diagnostics::unimplemented, "swizzle component out of range for type");
+                        getSink()->diagnose(swizExpr, Diagnostics::invalidSwizzleExpr, swizzleText, baseElementType->ToString());
                     }
                     anyError = true;
                     continue;