What causes "'null' filter is not applicable to primitive type {0}" in JetBrains/intellij-community?

Remove the 'null' filter for primitive-typed values; use 'true'/'false' for boolean or numeric equality filters where supported.

JetBrains/intellij-community · warning · SliceFilterParseException

slice.filter.parse.error.null.filter.not.applicable.for.primitive.type

slice.filter.parse.error.null.filter.not.applicable.for.primitive.type

Error message

'null' filter is not applicable to primitive type {0}

What it means

Thrown by JavaSliceProvider.parseFilter when a slice/view value filter of 'null' is applied to an expression whose type is a Java primitive (int, boolean, char, ...). Primitives cannot be null, so the null filter is meaningless there and a SliceFilterParseException is raised instead of producing an always-empty slice.

Source

Thrown at java/java-impl/src/com/intellij/slicer/JavaSliceProvider.java:122

      actionGroup.add(new CanItBeNullAction(sliceTreeBuilder));
    }
  }

  @Override
  public boolean supportValueFilters(@NotNull PsiElement expression) {
    PsiType type = getType(expression);
    return type != null && !PsiTypes.voidType().equals(type) && !PsiTypes.nullType().equals(type);
  }

  @Override
  public @NotNull SliceValueFilter parseFilter(@NotNull PsiElement expression, @NotNull String filter) throws SliceFilterParseException {
    PsiType type = getType(expression);
    if (type == null) {
      return SliceLanguageSupportProvider.super.parseFilter(expression, filter);
    }
    if (filter.equals("null")) {
      if (type instanceof PsiPrimitiveType) {
        throw new SliceFilterParseException(
          JavaBundle.message("slice.filter.parse.error.null.filter.not.applicable.for.primitive.type", type.getPresentableText()));
      }
      return new JavaValueFilter(DfTypes.NULL);
    }
    if (filter.equals("!null")) {
      if (type instanceof PsiPrimitiveType) {
        throw new SliceFilterParseException(
          JavaBundle.message("slice.filter.parse.error.not.null.filter.not.applicable.for.primitive.type", type.getPresentableText()));
      }
      return new JavaValueFilter(DfTypes.NOT_NULL_OBJECT);
    }
    RelationType relationType = RelationType.EQ;
    if (PsiTypes.byteType().equals(type) ||
        PsiTypes.charType().equals(type) ||
        PsiTypes.shortType().equals(type) ||
        PsiTypes.intType().equals(type) ||
        PsiTypes.longType().equals(type)) {
      for (RelationType relType : RelationType.values()) {

View on GitHub (pinned to be881553f2)

Solutions

Remove the 'null' filter for primitive-typed values; use 'true'/'false' for boolean or numeric equality filters where supported.
If nullability is what you care about, slice a boxed/wrapper expression (Integer) or the point where the value is boxed.
Check the expression's declared type in the slice tree before applying a 'null' filter.

Example fix

// before
int count = compute();
// slice of 'count' + filter 'null' -> throws
// after
Integer boxed = compute();
// slice of 'boxed' + filter 'null' -> valid

Defensive patterns

Strategy: type-guard

Validate before calling

PsiType type = JavaSliceProvider.getType(expression);
if (type instanceof PsiPrimitiveType && "null".equals(filterText)) {
  // reject the filter input early with a user-facing message
}

Type guard

static boolean supportsNullFilter(@Nullable PsiType t) {
  return t != null && !(t instanceof PsiPrimitiveType) && !PsiTypes.voidType().equals(t);
}

Try / catch

try { provider.parseFilter(expression, filter); } catch (SliceFilterParseException e) { /* invalid filter for this value's type; clear the filter box */ }

Prevention

Check the sliced value's type icon/declaration before typing 'null' filters.
Remember primitives can never be null; use boolean/numeric filters instead where offered.
Box the value (or slice at the boxing site) when you really need null-based slicing.

When it happens

Trigger: In the Slice tool window, invoking a value filter and typing 'null' while the sliced expression has a primitive type: slicing an int local, a boolean return value, a char field, etc.

Common situations: Users habitually typing 'null' filters after slicing reference expressions and switching to primitive ones; boxing confusion (Integer vs int) when reading the sliced type; typing 'null' into the filter for a method parameter of primitive type.

Related errors

AI-assisted analysis of JetBrains/intellij-community@be881553f2 (2026-08-14). Data as JSON: /api/errors/0407a94b30661480. Report an issue: GitHub.