ENH: snappyHexMesh: input checking. See #972.

src/mesh/snappyHexMesh/refinementFeatures/refinementFeatures.C

@@ -204,6 +204,14 @@ void Foam::refinementFeatures::read
                 distances_[featI][j] = distLevels[j].first();
                 levels_[featI][j] = distLevels[j].second();
 
+                if (levels_[featI][j] < 0)
+                {
+                    FatalErrorInFunction
+                        << "Feature " << featFileName
+                        << " has illegal refinement level " << levels_[featI][j]
+                        << exit(FatalError);
+                }
+
                 // Check in incremental order
                 if (j > 0)
                 {

src/mesh/snappyHexMesh/refinementSurfaces/refinementSurfaces.C

@@ -207,6 +207,7 @@ Foam::refinementSurfaces::refinementSurfaces
             (
                 globalMinLevel[surfI] < 0
              || globalMaxLevel[surfI] < globalMinLevel[surfI]
+             || globalMaxLevel[surfI] < 0
              || globalLevelIncr[surfI] < 0
             )
             {

src/mesh/snappyHexMesh/shellSurfaces/shellSurfaces.C

@@ -55,6 +55,8 @@ void Foam::shellSurfaces::setAndCheckLevels
     const List<Tuple2<scalar, label>>& distLevels
 )
 {
+    const searchableSurface& shell = allGeometry_[shells_[shellI]];
+
     if (modes_[shellI] != DISTANCE && distLevels.size() != 1)
     {
         FatalErrorInFunction
@@ -73,6 +75,16 @@ void Foam::shellSurfaces::setAndCheckLevels
         distances_[shellI][j] = distLevels[j].first();
         levels_[shellI][j] = distLevels[j].second();
 
+        if (levels_[shellI][j] < -1)
+        {
+            FatalErrorInFunction
+                << "Shell " << shell.name()
+                << " has illegal refinement level "
+                << levels_[shellI][j]
+                << exit(FatalError);
+        }
+
+
         // Check in incremental order
         if (j > 0)
         {
@@ -95,8 +107,6 @@ void Foam::shellSurfaces::setAndCheckLevels
         }
     }
 
-    const searchableSurface& shell = allGeometry_[shells_[shellI]];
-
     if (modes_[shellI] == DISTANCE)
     {
         Info<< "Refinement level according to distance to "