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, 24 insertions, 12 deletions

diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index 439bc7797..b1af6521c 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -55,15 +55,15 @@ namespace Slang
         }
     }
 
-    void IRUse::set(IRValue* usedValue)
+    void IRUse::set(IRValue* usedVal)
     {
         // clear out the old value
-        if (usedValue)
+        if (usedVal)
         {
             *prevLink = nextUse;
         }
 
-        init(user, usedValue);
+        init(user, usedVal);
     }
 
     void IRUse::clear()
@@ -3750,8 +3750,6 @@ namespace Slang
     {
         if( auto subtypeWitness = dynamic_cast<SubtypeWitness*>(val) )
         {
-            // We need to look up the IR value that represents the
-            // given subtype witness.
             String mangledName = getMangledNameForConformanceWitness(
                 subtypeWitness->sub,
                 subtypeWitness->sup);
@@ -3948,8 +3946,11 @@ namespace Slang
         // has already been made. To do that we will need to
         // compute the mangled name of the specialized function,
         // so that we can look for existing declarations.
-
-        String specMangledName = getMangledName(specDeclRef);
+        String specMangledName;
+        if (genericFunc->genericDecl == specDeclRef.decl)
+            specMangledName = getMangledName(specDeclRef);
+        else
+            specMangledName = mangleSpecializedFuncName(genericFunc->mangledName, specDeclRef.substitutions);
 
         // TODO: This is a terrible linear search, and we should
         // avoid it by building a dictionary ahead of time,
@@ -3992,8 +3993,8 @@ namespace Slang
         //
         // TODO: This shouldn't be needed, if we introduce a sorting
         // step before we emit code.
-        specFunc->removeFromParent();
-        specFunc->insertAfter(genericFunc);
+        //specFunc->removeFromParent();
+        //specFunc->insertAfter(genericFunc);
 
         // At this point we've created a new non-generic function,
         // which means we should add it to our work list for
@@ -4026,8 +4027,20 @@ namespace Slang
             auto keyDeclRef = ((IRDeclRef*) requirementKey)->declRef;
 
             // If the keys don't match, continue with the next entry.
-            if(!keyDeclRef.Equals(requirementDeclRef))
-                continue;
+            if (!keyDeclRef.Equals(requirementDeclRef))
+            {
+                // requirementDeclRef may be pointing to the inner decl of a generic decl
+                // in this case we compare keyDeclRef against the parent decl of requiredDeclRef
+                if (auto genRequiredDeclRef = requirementDeclRef.GetParent().As<GenericDecl>())
+                {
+                    if (!keyDeclRef.Equals(genRequiredDeclRef))
+                    {
+                        continue;
+                    }
+                }
+                else
+                    continue;
+            }
 
             // If the keys matched, then we use the value from
             // this entry.
@@ -4178,7 +4191,6 @@ namespace Slang
                             // Use the witness table to look up the value that
                             // satisfies the requirement.
                             auto satisfyingVal = findWitnessVal(witnessTable, requirementDeclRef);
-
                             // We expect to always find something, but lets just
                             // be careful here.
                             if(!satisfyingVal)