diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index af0df131e9c..8f3f28964c1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13202,12 +13202,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             const paramSymbol = createSymbol(
                 SymbolFlags.FunctionScopedVariable | (isOptional && !isRestParam ? SymbolFlags.Optional : 0),
                 paramName || `arg${i}` as __String,
+                isRestParam ? CheckFlags.RestParameter : isOptional ? CheckFlags.OptionalParameter : 0,
             );
             paramSymbol.links.type = isRestParam ? createArrayType(unionParamType) : unionParamType;
             params[i] = paramSymbol;
         }
         if (needsExtraRestElement) {
-            const restParamSymbol = createSymbol(SymbolFlags.FunctionScopedVariable, "args" as __String);
+            const restParamSymbol = createSymbol(SymbolFlags.FunctionScopedVariable, "args" as __String, CheckFlags.RestParameter);
             restParamSymbol.links.type = createArrayType(getTypeAtPosition(shorter, longestCount));
             if (shorter === right) {
                 restParamSymbol.links.type = instantiateType(restParamSymbol.links.type, mapper);
diff --git a/tests/baselines/reference/completionEntryForUnionMethod.baseline b/tests/baselines/reference/completionEntryForUnionMethod.baseline
index 8592e21eae6..58065fd8d6a 100644
--- a/tests/baselines/reference/completionEntryForUnionMethod.baseline
+++ b/tests/baselines/reference/completionEntryForUnionMethod.baseline
@@ -6,25 +6,25 @@
 // | (method) Array<T>.concat(...items: ConcatArray<string | number>[]): (string | number)[] (+1 overload)
 // | (method) Array<T>.every<S>(predicate: (value: string | number, index: number, array: (string | number)[]) => value is S, thisArg?: any): this is S[] (+1 overload)
 // | (method) Array<T>.filter<S>(predicate: (value: string | number, index: number, array: (string | number)[]) => value is S, thisArg?: any): S[] (+1 overload)
-// | (method) Array<T>.forEach(callbackfn: ((value: string, index: number, array: string[]) => void) & ((value: number, index: number, array: number[]) => void), thisArg: any): void
-// | (method) Array<T>.indexOf(searchElement: never, fromIndex: number): number
+// | (method) Array<T>.forEach(callbackfn: ((value: string, index: number, array: string[]) => void) & ((value: number, index: number, array: number[]) => void), thisArg?: any): void
+// | (method) Array<T>.indexOf(searchElement: never, fromIndex?: number): number
 // | (method) Array<T>.join(separator?: string): string
-// | (method) Array<T>.lastIndexOf(searchElement: never, fromIndex: number): number
+// | (method) Array<T>.lastIndexOf(searchElement: never, fromIndex?: number): number
 // | (property) Array<T>.length: number
-// | (method) Array<T>.map<unknown>(callbackfn: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg: any): unknown[]
+// | (method) Array<T>.map<unknown>(callbackfn: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg?: any): unknown[]
 // | (method) Array<T>.pop(): string | number
-// | (method) Array<T>.push(items: never[]): number
+// | (method) Array<T>.push(...items: never[]): number
 // | (method) Array<T>.reduce(callbackfn: (previousValue: string | number, currentValue: string | number, currentIndex: number, array: (string | number)[]) => string | number): string | number (+2 overloads)
 // | (method) Array<T>.reduceRight(callbackfn: (previousValue: string | number, currentValue: string | number, currentIndex: number, array: (string | number)[]) => string | number): string | number (+2 overloads)
 // | (method) Array<T>.reverse(): string[] | number[]
 // | (method) Array<T>.shift(): string | number
 // | (method) Array<T>.slice(start?: number, end?: number): string[] | number[]
-// | (method) Array<T>.some(predicate: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg: any): boolean
-// | (method) Array<T>.sort(compareFn: ((a: string, b: string) => number) & ((a: number, b: number) => number)): string[] | number[]
+// | (method) Array<T>.some(predicate: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg?: any): boolean
+// | (method) Array<T>.sort(compareFn?: ((a: string, b: string) => number) & ((a: number, b: number) => number)): string[] | number[]
 // | (method) Array<T>.splice(start: number, deleteCount?: number): string[] | number[] (+2 overloads)
 // | (method) Array<T>.toLocaleString(): string
 // | (method) Array<T>.toString(): string
-// | (method) Array<T>.unshift(items: never[]): number
+// | (method) Array<T>.unshift(...items: never[]): number
 // | ----------------------------------------------------------------------
 
 [
@@ -1263,6 +1263,10 @@
               "text": "thisArg",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -1413,6 +1417,10 @@
               "text": "fromIndex",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -1676,6 +1684,10 @@
               "text": "fromIndex",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -2120,6 +2132,10 @@
               "text": "thisArg",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -2340,6 +2356,10 @@
               "text": "(",
               "kind": "punctuation"
             },
+            {
+              "text": "...",
+              "kind": "punctuation"
+            },
             {
               "text": "items",
               "kind": "parameterName"
@@ -3803,6 +3823,10 @@
               "text": "thisArg",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -3929,6 +3953,10 @@
               "text": "compareFn",
               "kind": "parameterName"
             },
+            {
+              "text": "?",
+              "kind": "punctuation"
+            },
             {
               "text": ":",
               "kind": "punctuation"
@@ -4589,6 +4617,10 @@
               "text": "(",
               "kind": "punctuation"
             },
+            {
+              "text": "...",
+              "kind": "punctuation"
+            },
             {
               "text": "items",
               "kind": "parameterName"
diff --git a/tests/cases/fourslash/completionEntryForUnionMethod.ts b/tests/cases/fourslash/completionEntryForUnionMethod.ts
index 2804a373fd2..48dce525f32 100644
--- a/tests/cases/fourslash/completionEntryForUnionMethod.ts
+++ b/tests/cases/fourslash/completionEntryForUnionMethod.ts
@@ -3,7 +3,7 @@
 ////var y: Array<string>|Array<number>;
 ////y.map/**/(
 
-const text = "(method) Array<T>.map<unknown>(callbackfn: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg: any): unknown[]";
+const text = "(method) Array<T>.map<unknown>(callbackfn: ((value: string, index: number, array: string[]) => unknown) & ((value: number, index: number, array: number[]) => unknown), thisArg?: any): unknown[]";
 const documentation = "Calls a defined callback function on each element of an array, and returns an array that contains the results.";
 
 verify.quickInfoAt("", text, documentation);
diff --git a/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts b/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts
new file mode 100644
index 00000000000..dce4bfdf0ad
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoSignatureOptionalParameterFromUnion1.ts
@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts'/>
+
+// https://github.com/microsoft/TypeScript/issues/55574
+
+//// declare const optionals:
+////   | ((a?: { a: true }) => unknown)
+////   | ((b?: { b: true }) => unknown);
+////
+//// /**/optionals();
+
+verify.quickInfoAt(
+  "",
+  `const optionals: (arg0?: {
+    a: true;
+} & {
+    b: true;
+}) => unknown`,
+);
diff --git a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion1.ts b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion1.ts
new file mode 100644
index 00000000000..f407a3a4713
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion1.ts
@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts'/>
+
+// based on https://github.com/microsoft/TypeScript/issues/55574
+
+//// declare const rest:
+////   | ((v: { a: true }, ...rest: string[]) => unknown)
+////   | ((v: { b: true }) => unknown);
+////
+//// /**/rest({ a: true, b: true }, "foo", "bar");
+
+verify.quickInfoAt(
+  "",
+  `const rest: (v: {
+    a: true;
+} & {
+    b: true;
+}, ...rest: string[]) => unknown`,
+);
diff --git a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts
new file mode 100644
index 00000000000..d53beebd5d8
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion2.ts
@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts'/>
+
+// https://github.com/microsoft/TypeScript/issues/55574
+
+//// declare const rest:
+////   | ((a?: { a: true }, ...rest: string[]) => unknown)
+////   | ((b?: { b: true }) => unknown);
+////
+//// /**/rest({ a: true, b: true }, "foo", "bar");
+
+verify.quickInfoAt(
+  "",
+  `const rest: (arg0?: {
+    a: true;
+} & {
+    b: true;
+}, ...rest: string[]) => unknown`,
+);
diff --git a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion3.ts b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion3.ts
new file mode 100644
index 00000000000..506ab9942bd
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion3.ts
@@ -0,0 +1,22 @@
+/// <reference path='fourslash.ts'/>
+
+//// declare const fn:
+////   | ((a: { x: number }, b: { x: number }) => number)
+////   | ((...a: { y: number }[]) => number);
+////
+//// /**/fn();
+
+verify.quickInfoAt(
+  "",
+  `const fn: (a: {
+    x: number;
+} & {
+    y: number;
+}, b: {
+    x: number;
+} & {
+    y: number;
+}, ...args: {
+    y: number;
+}[]) => number`,
+);
diff --git a/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion4.ts b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion4.ts
new file mode 100644
index 00000000000..40e1882307e
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoSignatureRestParameterFromUnion4.ts
@@ -0,0 +1,22 @@
+/// <reference path='fourslash.ts'/>
+
+//// declare const fn:
+////   | ((a?: { x: number }, b?: { x: number }) => number)
+////   | ((...a: { y: number }[]) => number);
+////
+//// /**/fn();
+
+verify.quickInfoAt(
+  "",
+  `const fn: (a?: {
+    x: number;
+} & {
+    y: number;
+}, b?: {
+    x: number;
+} & {
+    y: number;
+}, ...args: {
+    y: number;
+}[]) => number`,
+);