---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: invalid.js
---
# Input
```jsx
switch(bar) { case 0: a(); case 1: b() }

switch(foo) { case 0: a(); default: b() }

switch (bar) { case 0: a(); default: b(); case 1: c() }

switch(foo) { case 0: if (a) { break; } default: b() }

switch(foo) { case 0: try { throw 0; } catch (err) {} default: b() }

switch(foo) { case 0: while (a) { break; } default: b() }

switch(foo) { case 0: do { break; } while (a); default: b() }

switch(foo) { case 0: {} default: b() }

switch(foo) { case 0: a(); { /* falls through */ } default: b() }

switch(foo) { case 0: { /* falls through */ } a(); default: b() }

switch(foo) { case 0: if (a) { /* falls through */ } default: b() }

switch(foo) { case 0: { { /* falls through */ } } default: b() }

switch(foo) { case 0: { /* comment */ } default: b() }

switch(foo) { case 0: a(); /* falling through */ default: b() }

switch(foo) { case 0: a(); /* no break */ case 1: b(); }

switch(foo) { case 0: a(); /* no break */ /* todo: fix readability */ default: b() }

switch(foo) { case 0: { a(); /* no break */ /* todo: fix readability */ } default: b() }

switch (a) { case 1: ; case 2: ; case 3: }

function f () {
    switch (a) {
        case 0:
            try { return foo(); } catch {} finally {}
        case 1:
            f();
    }
}

switch (foo) { case 0: {} case 1: case 2: f(); }

```

# Diagnostics
```
invalid.js:39:9 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    37 │ function f () {
    38 │     switch (a) {
  > 39 │         case 0:
       │         ^^^^^^^
  > 40 │             try { return foo(); } catch {} finally {}
       │             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    41 │         case 1:
    42 │             f();
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:1:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
  > 1 │ switch(bar) { case 0: a(); case 1: b() }
      │               ^^^^^^^^^^^^
    2 │ 
    3 │ switch(foo) { case 0: a(); default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:3:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    1 │ switch(bar) { case 0: a(); case 1: b() }
    2 │ 
  > 3 │ switch(foo) { case 0: a(); default: b() }
      │               ^^^^^^^^^^^^
    4 │ 
    5 │ switch (bar) { case 0: a(); default: b(); case 1: c() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:5:16 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    3 │ switch(foo) { case 0: a(); default: b() }
    4 │ 
  > 5 │ switch (bar) { case 0: a(); default: b(); case 1: c() }
      │                ^^^^^^^^^^^^
    6 │ 
    7 │ switch(foo) { case 0: if (a) { break; } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:5:29 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    3 │ switch(foo) { case 0: a(); default: b() }
    4 │ 
  > 5 │ switch (bar) { case 0: a(); default: b(); case 1: c() }
      │                             ^^^^^^^^^^^^^
    6 │ 
    7 │ switch(foo) { case 0: if (a) { break; } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:7:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    5 │ switch (bar) { case 0: a(); default: b(); case 1: c() }
    6 │ 
  > 7 │ switch(foo) { case 0: if (a) { break; } default: b() }
      │               ^^^^^^^^^^^^^^^^^^^^^^^^^
    8 │ 
    9 │ switch(foo) { case 0: try { throw 0; } catch (err) {} default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:9:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
     7 │ switch(foo) { case 0: if (a) { break; } default: b() }
     8 │ 
   > 9 │ switch(foo) { case 0: try { throw 0; } catch (err) {} default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    10 │ 
    11 │ switch(foo) { case 0: while (a) { break; } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:11:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
     9 │ switch(foo) { case 0: try { throw 0; } catch (err) {} default: b() }
    10 │ 
  > 11 │ switch(foo) { case 0: while (a) { break; } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    12 │ 
    13 │ switch(foo) { case 0: do { break; } while (a); default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:13:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    11 │ switch(foo) { case 0: while (a) { break; } default: b() }
    12 │ 
  > 13 │ switch(foo) { case 0: do { break; } while (a); default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    14 │ 
    15 │ switch(foo) { case 0: {} default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:15:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    13 │ switch(foo) { case 0: do { break; } while (a); default: b() }
    14 │ 
  > 15 │ switch(foo) { case 0: {} default: b() }
       │               ^^^^^^^^^^
    16 │ 
    17 │ switch(foo) { case 0: a(); { /* falls through */ } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:17:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    15 │ switch(foo) { case 0: {} default: b() }
    16 │ 
  > 17 │ switch(foo) { case 0: a(); { /* falls through */ } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    18 │ 
    19 │ switch(foo) { case 0: { /* falls through */ } a(); default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:19:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    17 │ switch(foo) { case 0: a(); { /* falls through */ } default: b() }
    18 │ 
  > 19 │ switch(foo) { case 0: { /* falls through */ } a(); default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    20 │ 
    21 │ switch(foo) { case 0: if (a) { /* falls through */ } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:21:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    19 │ switch(foo) { case 0: { /* falls through */ } a(); default: b() }
    20 │ 
  > 21 │ switch(foo) { case 0: if (a) { /* falls through */ } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    22 │ 
    23 │ switch(foo) { case 0: { { /* falls through */ } } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:23:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    21 │ switch(foo) { case 0: if (a) { /* falls through */ } default: b() }
    22 │ 
  > 23 │ switch(foo) { case 0: { { /* falls through */ } } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    24 │ 
    25 │ switch(foo) { case 0: { /* comment */ } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:25:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    23 │ switch(foo) { case 0: { { /* falls through */ } } default: b() }
    24 │ 
  > 25 │ switch(foo) { case 0: { /* comment */ } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^
    26 │ 
    27 │ switch(foo) { case 0: a(); /* falling through */ default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:27:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    25 │ switch(foo) { case 0: { /* comment */ } default: b() }
    26 │ 
  > 27 │ switch(foo) { case 0: a(); /* falling through */ default: b() }
       │               ^^^^^^^^^^^^
    28 │ 
    29 │ switch(foo) { case 0: a(); /* no break */ case 1: b(); }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:29:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    27 │ switch(foo) { case 0: a(); /* falling through */ default: b() }
    28 │ 
  > 29 │ switch(foo) { case 0: a(); /* no break */ case 1: b(); }
       │               ^^^^^^^^^^^^
    30 │ 
    31 │ switch(foo) { case 0: a(); /* no break */ /* todo: fix readability */ default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:31:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    29 │ switch(foo) { case 0: a(); /* no break */ case 1: b(); }
    30 │ 
  > 31 │ switch(foo) { case 0: a(); /* no break */ /* todo: fix readability */ default: b() }
       │               ^^^^^^^^^^^^
    32 │ 
    33 │ switch(foo) { case 0: { a(); /* no break */ /* todo: fix readability */ } default: b() }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:33:15 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    31 │ switch(foo) { case 0: a(); /* no break */ /* todo: fix readability */ default: b() }
    32 │ 
  > 33 │ switch(foo) { case 0: { a(); /* no break */ /* todo: fix readability */ } default: b() }
       │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    34 │ 
    35 │ switch (a) { case 1: ; case 2: ; case 3: }
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:35:14 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    33 │ switch(foo) { case 0: { a(); /* no break */ /* todo: fix readability */ } default: b() }
    34 │ 
  > 35 │ switch (a) { case 1: ; case 2: ; case 3: }
       │              ^^^^^^^^^
    36 │ 
    37 │ function f () {
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:35:24 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    33 │ switch(foo) { case 0: { a(); /* no break */ /* todo: fix readability */ } default: b() }
    34 │ 
  > 35 │ switch (a) { case 1: ; case 2: ; case 3: }
       │                        ^^^^^^^^^
    36 │ 
    37 │ function f () {
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```

```
invalid.js:46:16 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! This case is falling through to the next case.
  
    44 │ }
    45 │ 
  > 46 │ switch (foo) { case 0: {} case 1: case 2: f(); }
       │                ^^^^^^^^^^
    47 │ 
  
  i Add a `break` or `return` statement to the end of this case to prevent fallthrough.
  

```