resources/sksl/runtime_errors/IllegalIndexing.rts

// Legal cases that should not produce errors:
void literal_index()    { int a[2]; a[0] = 0; a[1] = a[0]; }
void const_var_index()  { int a[2]; const int b = 0; a[b] = 0; }
void loop_index()       { int a[2]; for (int i = 0; i <  2; ++i) { a[i]             = i; } }
void loop_expr_binary() { int a[2]; for (int i = 0; i <  2; ++i) { a[1 - i]         = i; } }
void loop_expr_unary()  { int a[2]; for (int i = 0; i > -2; --i) { a[-i]            = i; } }
void loop_swizzle()     { int a[2]; for (int i = 0; i <  2; ++i) { a[i.x]           = i; } }
void loop_ternary()     { int a[2]; for (int i = 0; i <  2; ++i) { a[i > 0 ? i : 0] = i; } }

void loop_type_coerce() { float a[2]; for (float i = 0; i < 2; ++i) { a[int(i)] = i; } }

void loop_nested() {
    int a[3];
    for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j) {
      a[i + j] = j;
    }
}

uniform int u;

// Illegal cases that should produce errors:
void uniform_index()    { int a[2]; a[u] = 0; }
void param_index(int p) { int a[2]; a[p] = 0; }

// Legal in SkSL when optimization is enabled:
void func_index()      { int a[2]; a[int(abs(-1))] = 0; }

/*%%*
error: 23: index expression must be constant
error: 24: index expression must be constant
*%%*/