Avoid creating programs with number of variables less than number of parameters

core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java

@@ -326,6 +326,11 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
 
         Program program = new Program();
         method.setProgram(program);
+
+        for (int i = 0; i <= method.parameterCount(); ++i) {
+            program.createVariable();
+        }
+
         BasicBlock block = program.createBasicBlock();
         Variable exceptionVar = program.createVariable();
         ConstructInstruction newExceptionInsn = new ConstructInstruction();

core/src/main/java/org/teavm/model/optimization/UnusedVariableElimination.java

@@ -29,6 +29,10 @@ public class UnusedVariableElimination implements MethodOptimization {
         boolean[] escaping = VariableEscapeAnalyzer.findEscapingVariables(program);
         boolean[] used = new boolean[escaping.length];
 
+        for (int i = 0; i <= method.parameterCount(); ++i) {
+            used[i] = true;
+        }
+
         int[] stack = new int[graph.size() * 2];
         int top = 0;
         for (int i = 0; i < used.length; ++i) {

core/src/main/java/org/teavm/model/util/TypeInferer.java

@@ -28,7 +28,7 @@ public class TypeInferer {
     GraphBuilder arrayElemBuilder;
 
     public void inferTypes(ProgramReader program, MethodReference method) {
-        int sz = Math.max(method.parameterCount(), program.variableCount());
+        int sz = program.variableCount();
         types = new VariableType[sz];
 
         types[0] = VariableType.OBJECT;