Allow constexpr macro definitions to be evaluated as constant

Author: tannergooding

sources/ClangSharp.PInvokeGenerator/PInvokeGenerator.VisitDecl.cs

@@ -3406,6 +3406,26 @@ private bool IsConstant(string targetTypeName, Expr initExpr)
 
                 case CX_StmtClass.CX_StmtClass_CallExpr:
                 {
+                    var callExpr = (CallExpr)initExpr;
+
+                    if (callExpr.DirectCallee.IsInlined)
+                    {
+                        var evaluateResult = callExpr.Handle.Evaluate;
+
+                        switch (evaluateResult.Kind)
+                        {
+                            case CXEvalResultKind.CXEval_Int:
+                            {
+                                return true;
+                            }
+
+                            case CXEvalResultKind.CXEval_Float:
+                            {
+                                return true;
+                            }
+                        }
+                    }
+
                     return false;
                 }
 

sources/ClangSharp.PInvokeGenerator/PInvokeGenerator.VisitStmt.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text;
@@ -68,6 +69,51 @@ private void VisitCallExpr(CallExpr callExpr)
             var outputBuilder = StartCSharpCode();
             var calleeDecl = callExpr.CalleeDecl;
 
+            if (callExpr.DirectCallee.IsInlined)
+            {
+                var evalResult = callExpr.Handle.Evaluate;
+                var canonicalType = callExpr.Type.CanonicalType;
+
+                switch (evalResult.Kind)
+                {
+                    case CXEvalResultKind.CXEval_Int:
+                    {
+                        if (canonicalType.Handle.IsUnsigned)
+                        {
+                            outputBuilder.Write(evalResult.AsUnsigned);
+                        }
+                        else
+                        {
+                            outputBuilder.Write(evalResult.AsLongLong);
+                        }
+
+                        StopCSharpCode();
+                        return;
+                    }
+
+                    case CXEvalResultKind.CXEval_Float:
+                    {
+                        if (canonicalType.Kind == CXTypeKind.CXType_Float)
+                        {
+                            outputBuilder.Write((float)evalResult.AsDouble);
+                        }
+                        else
+                        {
+                            outputBuilder.Write(evalResult.AsDouble);
+                        }
+
+                        StopCSharpCode();
+                        return;
+                    }
+
+                    case CXEvalResultKind.CXEval_StrLiteral:
+                    {
+                        AddDiagnostic(DiagnosticLevel.Info, "Possible string constant");
+                        break;
+                    }
+                }
+            }
+
             if (calleeDecl is null)
             {
                 Visit(callExpr.Callee);