From 1da9630a34981601a11ecbafff5f1afaef136031 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 26 Jul 2024 19:09:02 +0200
Subject: [PATCH] Bailout early from `isFunctionObjectType` for evolving arrays
 (#58049)

Co-authored-by: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
---
 src/compiler/checker.ts                       |  3 +
 ...ontainmentEvolvingArrayNoCrash1.errors.txt | 25 +++++++
 ...inContainmentEvolvingArrayNoCrash1.symbols | 36 ++++++++++
 ...hainContainmentEvolvingArrayNoCrash1.types | 68 +++++++++++++++++++
 ...alChainContainmentEvolvingArrayNoCrash1.ts | 18 +++++
 5 files changed, 150 insertions(+)
 create mode 100644 tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.errors.txt
 create mode 100644 tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.symbols
 create mode 100644 tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.types
 create mode 100644 tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 7f05c9b40df..78cee25efc9 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -27381,6 +27381,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function isFunctionObjectType(type: ObjectType): boolean {
+        if (getObjectFlags(type) & ObjectFlags.EvolvingArray) {
+            return false;
+        }
         // We do a quick check for a "bind" property before performing the more expensive subtype
         // check. This gives us a quicker out in the common case where an object type is not a function.
         const resolved = resolveStructuredTypeMembers(type);
diff --git a/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.errors.txt b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.errors.txt
new file mode 100644
index 00000000000..d503ac8d760
--- /dev/null
+++ b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.errors.txt
@@ -0,0 +1,25 @@
+narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts(1,5): error TS7034: Variable 'foo' implicitly has type 'any[]' in some locations where its type cannot be determined.
+narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts(5,5): error TS7005: Variable 'foo' implicitly has an 'any[]' type.
+
+
+==== narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts (2 errors) ====
+    let foo = [];
+        ~~~
+!!! error TS7034: Variable 'foo' implicitly has type 'any[]' in some locations where its type cannot be determined.
+    
+    switch (foo?.length) {
+      case 1:
+        foo[0];
+        ~~~
+!!! error TS7005: Variable 'foo' implicitly has an 'any[]' type.
+    }
+    
+    let bar = [];
+    
+    switch (bar?.length) {
+      case 1: {
+        bar.push("baz");
+        const arr: string[] = bar;
+      }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.symbols b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.symbols
new file mode 100644
index 00000000000..d766eadf659
--- /dev/null
+++ b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.symbols
@@ -0,0 +1,36 @@
+//// [tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts] ////
+
+=== narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts ===
+let foo = [];
+>foo : Symbol(foo, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 0, 3))
+
+switch (foo?.length) {
+>foo?.length : Symbol(Array.length, Decl(lib.es5.d.ts, --, --))
+>foo : Symbol(foo, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 0, 3))
+>length : Symbol(Array.length, Decl(lib.es5.d.ts, --, --))
+
+  case 1:
+    foo[0];
+>foo : Symbol(foo, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 0, 3))
+}
+
+let bar = [];
+>bar : Symbol(bar, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 7, 3))
+
+switch (bar?.length) {
+>bar?.length : Symbol(Array.length, Decl(lib.es5.d.ts, --, --))
+>bar : Symbol(bar, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 7, 3))
+>length : Symbol(Array.length, Decl(lib.es5.d.ts, --, --))
+
+  case 1: {
+    bar.push("baz");
+>bar.push : Symbol(Array.push, Decl(lib.es5.d.ts, --, --))
+>bar : Symbol(bar, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 7, 3))
+>push : Symbol(Array.push, Decl(lib.es5.d.ts, --, --))
+
+    const arr: string[] = bar;
+>arr : Symbol(arr, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 12, 9))
+>bar : Symbol(bar, Decl(narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts, 7, 3))
+  }
+}
+
diff --git a/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.types b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.types
new file mode 100644
index 00000000000..0a5d8998007
--- /dev/null
+++ b/tests/baselines/reference/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.types
@@ -0,0 +1,68 @@
+//// [tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts] ////
+
+=== narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts ===
+let foo = [];
+>foo : any[]
+>    : ^^^^^
+>[] : never[]
+>   : ^^^^^^^
+
+switch (foo?.length) {
+>foo?.length : number
+>            : ^^^^^^
+>foo : any[]
+>    : ^^^^^
+>length : number
+>       : ^^^^^^
+
+  case 1:
+>1 : 1
+>  : ^
+
+    foo[0];
+>foo[0] : any
+>       : ^^^
+>foo : any[]
+>    : ^^^^^
+>0 : 0
+>  : ^
+}
+
+let bar = [];
+>bar : any[]
+>    : ^^^^^
+>[] : never[]
+>   : ^^^^^^^
+
+switch (bar?.length) {
+>bar?.length : number
+>            : ^^^^^^
+>bar : any[]
+>    : ^^^^^
+>length : number
+>       : ^^^^^^
+
+  case 1: {
+>1 : 1
+>  : ^
+
+    bar.push("baz");
+>bar.push("baz") : number
+>                : ^^^^^^
+>bar.push : (...items: any[]) => number
+>         : ^^^^     ^^^^^^^^^^^^      
+>bar : any[]
+>    : ^^^^^
+>push : (...items: any[]) => number
+>     : ^^^^     ^^^^^^^^^^^^      
+>"baz" : "baz"
+>      : ^^^^^
+
+    const arr: string[] = bar;
+>arr : string[]
+>    : ^^^^^^^^
+>bar : string[]
+>    : ^^^^^^^^
+  }
+}
+
diff --git a/tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts b/tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts
new file mode 100644
index 00000000000..d20c1c1160f
--- /dev/null
+++ b/tests/cases/compiler/narrowSwitchOptionalChainContainmentEvolvingArrayNoCrash1.ts
@@ -0,0 +1,18 @@
+// @strict: true
+// @noEmit: true
+
+let foo = [];
+
+switch (foo?.length) {
+  case 1:
+    foo[0];
+}
+
+let bar = [];
+
+switch (bar?.length) {
+  case 1: {
+    bar.push("baz");
+    const arr: string[] = bar;
+  }
+}