feat(semantic/cfg): propagate unreachable edges through subgraphs. (#3648)

From this:

![Screenshot 2024-06-12 230152](https://github.com/oxc-project/oxc/assets/3788964/b489cee8-62ec-4483-9c9b-6e3d9858fec2)

To this:

![Screenshot 2024-06-12 230031](https://github.com/oxc-project/oxc/assets/3788964/674a6e42-5311-4ca6-940b-65d8e3ccc0f4)

crates/oxc_semantic/examples/cfg.rs

@@ -5,7 +5,10 @@ use oxc_allocator::Allocator;
 use oxc_parser::Parser;
 use oxc_semantic::{DebugDot, DisplayDot, EdgeType, SemanticBuilder};
 use oxc_span::SourceType;
-use petgraph::dot::{Config, Dot};
+use petgraph::{
+    dot::{Config, Dot},
+    visit::EdgeRef,
+};
 
 // Instruction:
 // 1. create a `test.js`,
@@ -91,8 +94,10 @@ fn main() -> std::io::Result<()> {
             &|_graph, edge| {
                 let weight = edge.weight();
                 let label = format!("label = \"{weight:?}\"");
-                if matches!(weight, EdgeType::Unreachable) {
+                if matches!(weight, EdgeType::Unreachable)
-                    format!("{label}, style = \"dotted\"")
+                    || semantic.semantic.cfg().basic_block(edge.source()).unreachable
+                {
+                    format!("{label}, style = \"dotted\" ")
                 } else {
                     label
                 }

crates/oxc_semantic/src/control_flow/builder/mod.rs

@@ -4,6 +4,7 @@ use crate::ReturnInstructionKind;
 use context::Ctx;
 
 pub use context::{CtxCursor, CtxFlags};
+use petgraph::Direction;
 
 use super::{
     AstNodeId, BasicBlock, BasicBlockId, CompactStr, ControlFlowGraph, EdgeType, ErrorEdgeKind,
@@ -56,6 +57,17 @@ impl<'a> ControlFlowGraphBuilder<'a> {
         self.basic_block_mut(self.current_node_ix)
     }
 
+    /// # Panics
+    pub fn basic_block(&self, basic_block: BasicBlockId) -> &BasicBlock {
+        let idx = *self
+            .graph
+            .node_weight(basic_block)
+            .expect("expected `self.current_node_ix` to be a valid node index in self.graph");
+        self.basic_blocks
+            .get(idx)
+            .expect("expected `self.current_node_ix` to be a valid node index in self.graph")
+    }
+
     /// # Panics
     pub fn basic_block_mut(&mut self, basic_block: BasicBlockId) -> &mut BasicBlock {
         let idx = *self
@@ -99,6 +111,20 @@ impl<'a> ControlFlowGraphBuilder<'a> {
     }
 
     pub fn add_edge(&mut self, a: BasicBlockId, b: BasicBlockId, weight: EdgeType) {
+        if matches!(weight, EdgeType::NewFunction) {
+            self.basic_block_mut(b).unreachable = false;
+        } else if self.basic_block(a).unreachable {
+            if self.graph.edges_directed(b, Direction::Incoming).count() == 0 {
+                self.basic_block_mut(b).unreachable = true;
+            }
+        } else if !self
+            .basic_block(b)
+            .instructions()
+            .iter()
+            .any(|it| matches!(it, Instruction { kind: InstructionKind::Unreachable, .. }))
+        {
+            self.basic_block_mut(b).unreachable = false;
+        }
         self.graph.add_edge(a, b, weight);
     }
 
@@ -193,12 +219,13 @@ impl<'a> ControlFlowGraphBuilder<'a> {
     pub fn append_unreachable(&mut self) {
         let current_node_ix = self.current_node_ix;
         let basic_block_with_unreachable_graph_ix = self.new_basic_block_normal();
+        self.push_instruction(InstructionKind::Unreachable, None);
+        self.current_basic_block().unreachable = true;
         self.add_edge(
             current_node_ix,
             basic_block_with_unreachable_graph_ix,
             EdgeType::Unreachable,
         );
-        self.push_instruction(InstructionKind::Unreachable, None);
     }
 
     #[inline]

crates/oxc_semantic/src/control_flow/dot.rs

@@ -3,7 +3,10 @@ use oxc_ast::{
     AstKind,
 };
 use oxc_syntax::node::AstNodeId;
-use petgraph::dot::{Config, Dot};
+use petgraph::{
+    dot::{Config, Dot},
+    visit::EdgeRef,
+};
 
 use crate::{
     AstNode, AstNodes, BasicBlock, ControlFlowGraph, EdgeType, Instruction, InstructionKind,
@@ -56,7 +59,9 @@ impl DisplayDot for ControlFlowGraph {
                 &|_graph, edge| {
                     let weight = edge.weight();
                     let label = format!("label = \"{weight:?}\" ");
-                    if matches!(weight, EdgeType::Unreachable) {
+                    if matches!(weight, EdgeType::Unreachable)
+                        || self.basic_block(edge.source()).unreachable
+                    {
                         format!("{label}, style = \"dotted\" ")
                     } else {
                         label
@@ -115,7 +120,9 @@ impl DebugDot for ControlFlowGraph {
                 &|_graph, edge| {
                     let weight = edge.weight();
                     let label = format!("label = \"{weight:?}\" ");
-                    if matches!(weight, EdgeType::Unreachable) {
+                    if matches!(weight, EdgeType::Unreachable)
+                        || self.basic_block(edge.source()).unreachable
+                    {
                         format!("{label}, style = \"dotted\" ")
                     } else {
                         label

crates/oxc_semantic/src/control_flow/mod.rs

@@ -116,11 +116,12 @@ pub enum CallType {
 #[derive(Debug)]
 pub struct BasicBlock {
     pub instructions: Vec<Instruction>,
+    pub unreachable: bool,
 }
 
 impl BasicBlock {
     fn new() -> Self {
-        BasicBlock { instructions: Vec::new() }
+        BasicBlock { instructions: Vec::new(), unreachable: false }
     }
 
     pub fn instructions(&self) -> &Vec<Instruction> {

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@break_from_a_label_in_global_scope.js-2.snap

@@ -9,9 +9,9 @@ digraph {
     2 [ label = "unreachable" ]
     3 [ label = "" ]
     1 -> 0 [ label = "Error(Implicit)" ]
-    2 -> 0 [ label = "Error(Implicit)" ]
+    2 -> 0 [ label = "Error(Implicit)" , style = "dotted" ]
     1 -> 2 [ label = "Unreachable" , style = "dotted" ]
     3 -> 0 [ label = "Error(Implicit)" ]
-    2 -> 3 [ label = "Normal" ]
+    2 -> 3 [ label = "Normal" , style = "dotted" ]
     1 -> 3 [ label = "Jump" ]
 }

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@class_extend_super.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@do_while_break.js-2.snap

@@ -25,14 +25,14 @@ digraph {
     6 -> 2 [ label = "Error(Implicit)" ]
     4 -> 6 [ label = "Normal" ]
     7 -> 2 [ label = "Error(Implicit)" ]
-    8 -> 2 [ label = "Error(Implicit)" ]
+    8 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     7 -> 8 [ label = "Unreachable" , style = "dotted" ]
-    9 -> 2 [ label = "Error(Implicit)" ]
+    9 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     10 -> 2 [ label = "Error(Implicit)" ]
     6 -> 7 [ label = "Normal" ]
-    8 -> 9 [ label = "Normal" ]
+    8 -> 9 [ label = "Normal" , style = "dotted" ]
-    9 -> 10 [ label = "Normal" ]
+    9 -> 10 [ label = "Normal" , style = "dotted" ]
-    9 -> 7 [ label = "Backedge" ]
+    9 -> 7 [ label = "Backedge" , style = "dotted" ]
     7 -> 10 [ label = "Jump" ]
     11 -> 2 [ label = "Error(Implicit)" ]
     3 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@fn_return_obj_expr_with_computed_key.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@if_else.js-2.snap

@@ -28,18 +28,18 @@ digraph {
     4 -> 6 [ label = "Normal" ]
     5 -> 6 [ label = "Normal" ]
     7 -> 2 [ label = "Error(Implicit)" ]
-    8 -> 2 [ label = "Error(Implicit)" ]
+    8 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     7 -> 8 [ label = "Unreachable" , style = "dotted" ]
     9 -> 2 [ label = "Error(Implicit)" ]
-    10 -> 2 [ label = "Error(Implicit)" ]
+    10 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     9 -> 10 [ label = "Unreachable" , style = "dotted" ]
-    11 -> 2 [ label = "Error(Implicit)" ]
+    11 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Normal" ]
-    8 -> 11 [ label = "Normal" ]
+    8 -> 11 [ label = "Normal" , style = "dotted" ]
     6 -> 7 [ label = "Jump" ]
     3 -> 9 [ label = "Normal" ]
-    10 -> 11 [ label = "Normal" ]
+    10 -> 11 [ label = "Normal" , style = "dotted" ]
-    12 -> 2 [ label = "Error(Implicit)" ]
+    12 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     11 -> 12 [ label = "Unreachable" , style = "dotted" ]
     13 -> 0 [ label = "Error(Implicit)" ]
     1 -> 13 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@if_stmt_in_for_in.js-2.snap

@@ -30,21 +30,21 @@ digraph {
     6 -> 2 [ label = "Error(Implicit)" ]
     7 -> 2 [ label = "Error(Implicit)" ]
     8 -> 2 [ label = "Error(Implicit)" ]
-    9 -> 2 [ label = "Error(Implicit)" ]
+    9 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     8 -> 9 [ label = "Unreachable" , style = "dotted" ]
     10 -> 2 [ label = "Error(Implicit)" ]
     11 -> 2 [ label = "Error(Implicit)" ]
     12 -> 2 [ label = "Error(Implicit)" ]
-    13 -> 2 [ label = "Error(Implicit)" ]
+    13 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     12 -> 13 [ label = "Unreachable" , style = "dotted" ]
     14 -> 2 [ label = "Error(Implicit)" ]
     10 -> 11 [ label = "Normal" ]
-    13 -> 14 [ label = "Normal" ]
+    13 -> 14 [ label = "Normal" , style = "dotted" ]
     11 -> 12 [ label = "Jump" ]
     10 -> 14 [ label = "Normal" ]
     15 -> 2 [ label = "Error(Implicit)" ]
     6 -> 7 [ label = "Normal" ]
-    9 -> 15 [ label = "Normal" ]
+    9 -> 15 [ label = "Normal" , style = "dotted" ]
     7 -> 8 [ label = "Jump" ]
     6 -> 10 [ label = "Normal" ]
     14 -> 15 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@labeled_block_break.js-2.snap

@@ -21,11 +21,11 @@ digraph {
     2 -> 4 [ label = "Normal" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     6 -> 0 [ label = "Error(Implicit)" ]
-    7 -> 0 [ label = "Error(Implicit)" ]
+    7 -> 0 [ label = "Error(Implicit)" , style = "dotted" ]
     6 -> 7 [ label = "Unreachable" , style = "dotted" ]
     8 -> 0 [ label = "Error(Implicit)" ]
     4 -> 5 [ label = "Normal" ]
-    7 -> 8 [ label = "Normal" ]
+    7 -> 8 [ label = "Normal" , style = "dotted" ]
     5 -> 6 [ label = "Jump" ]
     4 -> 8 [ label = "Normal" ]
     9 -> 0 [ label = "Error(Implicit)" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@labelled_try_break.js-2.snap

@@ -22,20 +22,20 @@ digraph {
     1 -> 3 [ label = "NewFunction" ]
     5 -> 2 [ label = "Error(Implicit)" ]
     5 -> 4 [ label = "Finalize" ]
-    6 -> 2 [ label = "Error(Implicit)" ]
+    6 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
-    6 -> 4 [ label = "Finalize" ]
+    6 -> 4 [ label = "Finalize" , style = "dotted" ]
     5 -> 6 [ label = "Unreachable" , style = "dotted" ]
     7 -> 2 [ label = "Error(Implicit)" ]
     4 -> 7 [ label = "Normal" ]
-    8 -> 2 [ label = "Error(Implicit)" ]
+    8 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     7 -> 8 [ label = "Unreachable" , style = "dotted" ]
-    9 -> 2 [ label = "Error(Implicit)" ]
+    9 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 5 [ label = "Normal" ]
-    8 -> 9 [ label = "Join" ]
+    8 -> 9 [ label = "Join" , style = "dotted" ]
     10 -> 2 [ label = "Error(Implicit)" ]
-    9 -> 10 [ label = "Normal" ]
+    9 -> 10 [ label = "Normal" , style = "dotted" ]
     7 -> 10 [ label = "Jump" ]
-    11 -> 2 [ label = "Error(Implicit)" ]
+    11 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     10 -> 11 [ label = "Unreachable" , style = "dotted" ]
     12 -> 0 [ label = "Error(Implicit)" ]
     1 -> 12 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@member_access_with_numbered_index.js-2.snap

@@ -14,9 +14,9 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
-    5 -> 2 [ label = "Error(Implicit)" ]
+    5 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     4 -> 5 [ label = "Unreachable" , style = "dotted" ]
     6 -> 0 [ label = "Error(Implicit)" ]
     1 -> 6 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@member_access_with_unreachable.js-2.snap

@@ -14,9 +14,9 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
-    5 -> 2 [ label = "Error(Implicit)" ]
+    5 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     4 -> 5 [ label = "Unreachable" , style = "dotted" ]
     6 -> 0 [ label = "Error(Implicit)" ]
     1 -> 6 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@nested_computed_member_expression.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@private_in.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@simple_spread.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@spread_in_a_spread.js-2.snap

@@ -13,7 +13,7 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@switch_in_while.js-2.snap

@@ -21,13 +21,13 @@ digraph {
     4 -> 0 [ label = "Error(Implicit)" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     4 -> 5 [ label = "Jump" ]
-    6 -> 0 [ label = "Error(Implicit)" ]
+    6 -> 0 [ label = "Error(Implicit)" , style = "dotted" ]
     5 -> 6 [ label = "Unreachable" , style = "dotted" ]
     7 -> 0 [ label = "Error(Implicit)" ]
     8 -> 0 [ label = "Error(Implicit)" ]
     7 -> 8 [ label = "Jump" ]
     4 -> 7 [ label = "Normal" ]
-    6 -> 7 [ label = "Normal" ]
+    6 -> 7 [ label = "Normal" , style = "dotted" ]
     3 -> 4 [ label = "Normal" ]
     3 -> 7 [ label = "Normal" ]
     9 -> 0 [ label = "Error(Implicit)" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@switch_statement.js-2.snap

@@ -33,7 +33,7 @@ digraph {
     4 -> 2 [ label = "Error(Implicit)" ]
     5 -> 2 [ label = "Error(Implicit)" ]
     4 -> 5 [ label = "Jump" ]
-    6 -> 2 [ label = "Error(Implicit)" ]
+    6 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     5 -> 6 [ label = "Unreachable" , style = "dotted" ]
     7 -> 2 [ label = "Error(Implicit)" ]
     8 -> 2 [ label = "Error(Implicit)" ]
@@ -41,12 +41,12 @@ digraph {
     9 -> 2 [ label = "Error(Implicit)" ]
     10 -> 2 [ label = "Error(Implicit)" ]
     9 -> 10 [ label = "Jump" ]
-    11 -> 2 [ label = "Error(Implicit)" ]
+    11 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     10 -> 11 [ label = "Unreachable" , style = "dotted" ]
     12 -> 2 [ label = "Error(Implicit)" ]
     13 -> 2 [ label = "Error(Implicit)" ]
     12 -> 13 [ label = "Jump" ]
-    14 -> 2 [ label = "Error(Implicit)" ]
+    14 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     13 -> 14 [ label = "Unreachable" , style = "dotted" ]
     15 -> 2 [ label = "Error(Implicit)" ]
     16 -> 2 [ label = "Error(Implicit)" ]
@@ -54,14 +54,14 @@ digraph {
     17 -> 2 [ label = "Error(Implicit)" ]
     18 -> 2 [ label = "Error(Implicit)" ]
     17 -> 18 [ label = "Jump" ]
-    19 -> 2 [ label = "Error(Implicit)" ]
+    19 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     18 -> 19 [ label = "Unreachable" , style = "dotted" ]
     4 -> 7 [ label = "Normal" ]
     4 -> 9 [ label = "Normal" ]
     4 -> 12 [ label = "Normal" ]
     4 -> 15 [ label = "Normal" ]
     4 -> 17 [ label = "Normal" ]
-    6 -> 7 [ label = "Normal" ]
+    6 -> 7 [ label = "Normal" , style = "dotted" ]
     3 -> 4 [ label = "Normal" ]
     7 -> 9 [ label = "Normal" ]
     7 -> 12 [ label = "Normal" ]
@@ -72,21 +72,21 @@ digraph {
     9 -> 12 [ label = "Normal" ]
     9 -> 15 [ label = "Normal" ]
     9 -> 17 [ label = "Normal" ]
-    11 -> 12 [ label = "Normal" ]
+    11 -> 12 [ label = "Normal" , style = "dotted" ]
     3 -> 9 [ label = "Normal" ]
     12 -> 15 [ label = "Normal" ]
     12 -> 17 [ label = "Normal" ]
-    14 -> 15 [ label = "Normal" ]
+    14 -> 15 [ label = "Normal" , style = "dotted" ]
     3 -> 12 [ label = "Normal" ]
     15 -> 17 [ label = "Normal" ]
     16 -> 17 [ label = "Normal" ]
     3 -> 15 [ label = "Normal" ]
     3 -> 17 [ label = "Normal" ]
     20 -> 2 [ label = "Error(Implicit)" ]
-    19 -> 20 [ label = "Normal" ]
+    19 -> 20 [ label = "Normal" , style = "dotted" ]
     5 -> 20 [ label = "Jump" ]
     10 -> 20 [ label = "Jump" ]
-    21 -> 2 [ label = "Error(Implicit)" ]
+    21 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     20 -> 21 [ label = "Unreachable" , style = "dotted" ]
     22 -> 0 [ label = "Error(Implicit)" ]
     1 -> 22 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@two_functions.js-2.snap

@@ -17,13 +17,13 @@ digraph {
     1 -> 0 [ label = "Error(Implicit)" ]
     3 -> 2 [ label = "Error(Implicit)" ]
     1 -> 3 [ label = "NewFunction" ]
-    4 -> 2 [ label = "Error(Implicit)" ]
+    4 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     3 -> 4 [ label = "Unreachable" , style = "dotted" ]
     5 -> 0 [ label = "Error(Implicit)" ]
     1 -> 5 [ label = "Normal" ]
     7 -> 6 [ label = "Error(Implicit)" ]
     5 -> 7 [ label = "NewFunction" ]
-    8 -> 6 [ label = "Error(Implicit)" ]
+    8 -> 6 [ label = "Error(Implicit)" , style = "dotted" ]
     7 -> 8 [ label = "Unreachable" , style = "dotted" ]
     9 -> 0 [ label = "Error(Implicit)" ]
     5 -> 9 [ label = "Normal" ]

crates/oxc_semantic/tests/integration/snapshots/integration__cfg__cfg_files@while.js-2.snap

@@ -26,14 +26,14 @@ digraph {
     4 -> 6 [ label = "Normal" ]
     5 -> 6 [ label = "Normal" ]
     7 -> 2 [ label = "Error(Implicit)" ]
-    8 -> 2 [ label = "Error(Implicit)" ]
+    8 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     7 -> 8 [ label = "Unreachable" , style = "dotted" ]
     9 -> 2 [ label = "Error(Implicit)" ]
     3 -> 4 [ label = "Normal" ]
     4 -> 7 [ label = "Jump" ]
-    8 -> 4 [ label = "Backedge" ]
+    8 -> 4 [ label = "Backedge" , style = "dotted" ]
     4 -> 9 [ label = "Normal" ]
-    10 -> 2 [ label = "Error(Implicit)" ]
+    10 -> 2 [ label = "Error(Implicit)" , style = "dotted" ]
     9 -> 10 [ label = "Unreachable" , style = "dotted" ]
     11 -> 0 [ label = "Error(Implicit)" ]
     1 -> 11 [ label = "Normal" ]