From 7ada00790c88f4d7f9dfd365a3a78e67da642c01 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Fri, 17 May 2019 14:33:38 +0200
Subject: [PATCH] cgo: print better error messages for unknown types

Types used in a program may not be implemented. Print a nice error
message explaining the situation, instead of just prepending C. to the
type spelling (and hoping the user knows what that undefined reference
means).
---
 cgo/libclang.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/cgo/libclang.go b/cgo/libclang.go
index cca4487e..ce6df766 100644
--- a/cgo/libclang.go
+++ b/cgo/libclang.go
@@ -613,9 +613,15 @@ func (p *cgoPackage) makeASTType(typ C.CXType, pos token.Pos) ast.Expr {
 		}
 	}
 	if typeName == "" {
+		// Report this as an error.
+		spelling := getString(C.clang_getTypeSpelling(typ))
+		p.errors = append(p.errors, scanner.Error{
+			Pos: p.fset.PositionFor(pos, true),
+			Msg: fmt.Sprintf("unknown C type: %v (libclang type kind %d)", spelling, typ.kind),
+		})
 		// Fallback, probably incorrect but at least the error points to an odd
 		// type name.
-		typeName = "C." + getString(C.clang_getTypeSpelling(typ))
+		typeName = "C." + spelling
 	}
 	return &ast.Ident{
 		NamePos: pos,