Work towards target-specific function overloads (#210)

* Checkpoint: interface conformance work

- Add explicit definition of `saturate` for the GLSL target, which calls through to `clamp`

- Needed to add explicit initializer to `__BuiltinFloatingPointType` to allow initialization from a single `float`, so that the `saturate` implementation can be sure that it can initialize a `T` from `0.0` or `1.0`.

- This triggered errors in overload resolution, because the logic in place could not figure out that the `T` of the outer generic (`saturate<T>()`) conformed to the interface required by the callee.

At this point I have the call to the scalar `clamp()` getting past type-checking, but not the vector or matrix cases.

* More fixups for overload resolution inside generics

- Make sure value parameters are treated the same as type parameters: we only want to solve for the parameters of the generic actually being applied, and not accidentally generate constraints for outer generics (e.g., when checking the body of a generic function).

- Make sure that the diagnostics stuff uses the correct source manager when expanding the location of a builtin.

* Fixes for function redeclaration

- Handle case of redeclaring a generic function
  - Enumerate siblings in the parent of the *generic* not the parent of the *function*
  - Add logic to compare generic signatures
  - When generic signatures match, specialize functions to compatible generic arguments before comparing the function signatures

- Fix redeclaration logic to *not* detect prefix/postifx operators as redeclarations of one another

- Build an explicit representation of function redeclaration groups
  - First declaration is the "primary" and others are stored in a linked list

- Make overload resolution handle redeclared functions
  - Only consider the primary declaration and skip others

1 files changed, 9 insertions, 0 deletions

diff --git a/source/slang/modifier-defs.h b/source/slang/modifier-defs.h
index 9a16a0bdd..c563d35cf 100644
--- a/source/slang/modifier-defs.h
+++ b/source/slang/modifier-defs.h
@@ -49,6 +49,15 @@ SYNTAX_CLASS(TargetIntrinsicModifier, Modifier)
     FIELD(Token, definitionToken)
 END_SYNTAX_CLASS()
 
+// A modifier that marks a declaration as representing a
+// specialization that should be preferred on a particular
+// target.
+SYNTAX_CLASS(SpecializedForTargetModifier, Modifier)
+    // Token that names the target that the operation
+    // has been specialized for.
+    FIELD(Token, targetToken)
+END_SYNTAX_CLASS()
+
 // A modifier to tag something as an intrinsic that requires
 // a certain GLSL extension to be enabled when used
 SYNTAX_CLASS(RequiredGLSLExtensionModifier, Modifier)