From f8453ccb734c9c5ba81f60ff1c386d39159c7326 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 11 Mar 2026 17:00:26 +0000
Subject: [PATCH] Fix strictPropertyInitialization check to use effective value
 and add tests

Co-authored-by: RyanCavanaugh <6685088+RyanCavanaugh@users.noreply.github.com>
---
 src/compiler/program.ts                       |  2 +-
 ...onalPropertyTypesWithDefaultStrict.symbols | 18 ++++++++++++++++++
 ...tionalPropertyTypesWithDefaultStrict.types | 19 +++++++++++++++++++
 ...lizationDefaultStrictNullChecks.errors.txt | 15 +++++++++++++++
 ...tializationDefaultStrictNullChecks.symbols | 17 +++++++++++++++++
 ...nitializationDefaultStrictNullChecks.types | 19 +++++++++++++++++++
 ...tOptionalPropertyTypesWithDefaultStrict.ts | 12 ++++++++++++
 ...tyInitializationDefaultStrictNullChecks.ts | 12 ++++++++++++
 8 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.symbols
 create mode 100644 tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.types
 create mode 100644 tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.errors.txt
 create mode 100644 tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.symbols
 create mode 100644 tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.types
 create mode 100644 tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts
 create mode 100644 tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 69d10046a4c..23c2a56ef04 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -4070,7 +4070,7 @@ export function createProgram(_rootNamesOrOptions: readonly string[] | CreatePro
     }
 
     function verifyCompilerOptions() {
-        if (options.strictPropertyInitialization && !getStrictOptionValue(options, "strictNullChecks")) {
+        if (getStrictOptionValue(options, "strictPropertyInitialization") && !getStrictOptionValue(options, "strictNullChecks")) {
             createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_without_specifying_option_1, "strictPropertyInitialization", "strictNullChecks");
         }
         if (options.exactOptionalPropertyTypes && !getStrictOptionValue(options, "strictNullChecks")) {
diff --git a/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.symbols b/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.symbols
new file mode 100644
index 00000000000..1adc8dd3413
--- /dev/null
+++ b/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.symbols
@@ -0,0 +1,18 @@
+//// [tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts] ////
+
+=== exactOptionalPropertyTypesWithDefaultStrict.ts ===
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictNullChecks is effectively true, so exactOptionalPropertyTypes
+// should work without producing TS5052.
+
+interface Foo {
+>Foo : Symbol(Foo, Decl(exactOptionalPropertyTypesWithDefaultStrict.ts, 0, 0))
+
+    bar?: string;
+>bar : Symbol(Foo.bar, Decl(exactOptionalPropertyTypesWithDefaultStrict.ts, 4, 15))
+}
+
+const foo: Foo = {};
+>foo : Symbol(foo, Decl(exactOptionalPropertyTypesWithDefaultStrict.ts, 8, 5))
+>Foo : Symbol(Foo, Decl(exactOptionalPropertyTypesWithDefaultStrict.ts, 0, 0))
+
diff --git a/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.types b/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.types
new file mode 100644
index 00000000000..d01e8c73192
--- /dev/null
+++ b/tests/baselines/reference/exactOptionalPropertyTypesWithDefaultStrict.types
@@ -0,0 +1,19 @@
+//// [tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts] ////
+
+=== exactOptionalPropertyTypesWithDefaultStrict.ts ===
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictNullChecks is effectively true, so exactOptionalPropertyTypes
+// should work without producing TS5052.
+
+interface Foo {
+    bar?: string;
+>bar : string | undefined
+>    : ^^^^^^^^^^^^^^^^^^
+}
+
+const foo: Foo = {};
+>foo : Foo
+>    : ^^^
+>{} : {}
+>   : ^^
+
diff --git a/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.errors.txt b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.errors.txt
new file mode 100644
index 00000000000..59e09d61dcd
--- /dev/null
+++ b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.errors.txt
@@ -0,0 +1,15 @@
+error TS5052: Option 'strictPropertyInitialization' cannot be specified without specifying option 'strictNullChecks'.
+
+
+!!! error TS5052: Option 'strictPropertyInitialization' cannot be specified without specifying option 'strictNullChecks'.
+==== strictPropertyInitializationDefaultStrictNullChecks.ts (0 errors) ====
+    // When strict is not specified, it defaults to true in TS 6.0.
+    // strictPropertyInitialization is effectively true via the strict default.
+    // Specifying strictNullChecks: false should produce an error because
+    // strictPropertyInitialization requires strictNullChecks.
+    
+    class C {
+        x: number;
+        constructor() {}
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.symbols b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.symbols
new file mode 100644
index 00000000000..90636cf313f
--- /dev/null
+++ b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.symbols
@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts] ////
+
+=== strictPropertyInitializationDefaultStrictNullChecks.ts ===
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictPropertyInitialization is effectively true via the strict default.
+// Specifying strictNullChecks: false should produce an error because
+// strictPropertyInitialization requires strictNullChecks.
+
+class C {
+>C : Symbol(C, Decl(strictPropertyInitializationDefaultStrictNullChecks.ts, 0, 0))
+
+    x: number;
+>x : Symbol(C.x, Decl(strictPropertyInitializationDefaultStrictNullChecks.ts, 5, 9))
+
+    constructor() {}
+}
+
diff --git a/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.types b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.types
new file mode 100644
index 00000000000..172d5f20639
--- /dev/null
+++ b/tests/baselines/reference/strictPropertyInitializationDefaultStrictNullChecks.types
@@ -0,0 +1,19 @@
+//// [tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts] ////
+
+=== strictPropertyInitializationDefaultStrictNullChecks.ts ===
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictPropertyInitialization is effectively true via the strict default.
+// Specifying strictNullChecks: false should produce an error because
+// strictPropertyInitialization requires strictNullChecks.
+
+class C {
+>C : C
+>  : ^
+
+    x: number;
+>x : number
+>  : ^^^^^^
+
+    constructor() {}
+}
+
diff --git a/tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts b/tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts
new file mode 100644
index 00000000000..0ab42117c3c
--- /dev/null
+++ b/tests/cases/compiler/exactOptionalPropertyTypesWithDefaultStrict.ts
@@ -0,0 +1,12 @@
+// @exactOptionalPropertyTypes: true
+// @noEmit: true
+
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictNullChecks is effectively true, so exactOptionalPropertyTypes
+// should work without producing TS5052.
+
+interface Foo {
+    bar?: string;
+}
+
+const foo: Foo = {};
diff --git a/tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts b/tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts
new file mode 100644
index 00000000000..8094cfc9c85
--- /dev/null
+++ b/tests/cases/compiler/strictPropertyInitializationDefaultStrictNullChecks.ts
@@ -0,0 +1,12 @@
+// @strictNullChecks: false
+// @noEmit: true
+
+// When strict is not specified, it defaults to true in TS 6.0.
+// strictPropertyInitialization is effectively true via the strict default.
+// Specifying strictNullChecks: false should produce an error because
+// strictPropertyInitialization requires strictNullChecks.
+
+class C {
+    x: number;
+    constructor() {}
+}