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, 16 insertions, 0 deletions

diff --git a/source/slang/decl-defs.h b/source/slang/decl-defs.h
index f27ab9ba6..c9860f9bf 100644
--- a/source/slang/decl-defs.h
+++ b/source/slang/decl-defs.h
@@ -127,6 +127,22 @@ ABSTRACT_SYNTAX_CLASS(CallableDecl, ContainerDecl)
     })
 
     SYNTAX_FIELD(TypeExp, ReturnType)
+
+    // Fields related to redeclaration, so that we
+    // can support multiple specialized varaitions
+    // of the "same" logical function.
+    //
+    // This should also help us to support redeclaration
+    // of functions when handling HLSL/GLSL.
+
+    // The "primary" declaration of the function, which will
+    // be used whenever we need to unique things.
+    FIELD_INIT(CallableDecl*, primaryDecl, nullptr)
+
+    // The next declaration of the "same" function (that is,
+    // with the same `primaryDecl`).
+    FIELD_INIT(CallableDecl*, nextDecl, nullptr);
+
 END_SYNTAX_CLASS()
 
 // Base class for callable things that may also have a body that is evaluated to produce their result