Fix T49136: full constant Curves with zero Fac input crashes in assert.

The if branches were reordered when the original patch was
committed, which broke the implicit non-NULL guarantee on link.

To prevent re-occurrence, add a couple of unit tests.

1 files changed, 6 insertions, 5 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 4f54b86fe4a..0304d6d95d1 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -4846,12 +4846,8 @@ void CurvesNode::constant_fold(const ConstantFolder& folder, ShaderInput *value_
 {
 	ShaderInput *fac_in = input("Fac");
 
-	/* remove no-op node */
-	if(!fac_in->link && fac == 0.0f) {
-		folder.bypass(value_in->link);
-	}
 	/* evaluate fully constant node */
-	else if(folder.all_inputs_constant()) {
+	if(folder.all_inputs_constant()) {
 		if (curves.size() == 0)
 			return;
 
@@ -4864,6 +4860,11 @@ void CurvesNode::constant_fold(const ConstantFolder& folder, ShaderInput *value_
 
 		folder.make_constant(interp(value, result, fac));
 	}
+	/* remove no-op node */
+	else if(!fac_in->link && fac == 0.0f) {
+		/* link is not null because otherwise all inputs are constant */
+		folder.bypass(value_in->link);
+	}
 }
 
 void CurvesNode::compile(SVMCompiler& compiler, int type, ShaderInput *value_in, ShaderOutput *value_out)