diff --git a/src/lib/es5.d.ts b/src/lib/es5.d.ts
index 4c3c558916ff1..422f8cdfb2bc6 100644
--- a/src/lib/es5.d.ts
+++ b/src/lib/es5.d.ts
@@ -1376,7 +1376,7 @@ interface ArrayConstructor {
     (arrayLength?: number): any[];
     <T>(arrayLength: number): T[];
     <T>(...items: T[]): T[];
-    isArray<T>(arg: T | {}): arg is T extends readonly any[] ? (unknown extends T ? never : readonly any[]) : any[];
+    isArray(arg: any): arg is any[];
     readonly prototype: any[];
 }
 
diff --git a/tests/baselines/reference/consistentUnionSubtypeReduction.js b/tests/baselines/reference/consistentUnionSubtypeReduction.js
deleted file mode 100644
index ce583be6d33e9..0000000000000
--- a/tests/baselines/reference/consistentUnionSubtypeReduction.js
+++ /dev/null
@@ -1,100 +0,0 @@
-//// [consistentUnionSubtypeReduction.ts]
-// https://github.com/microsoft/TypeScript/issues/31155
-
-declare const MyArray: {
-    isArray<T>(arg: T | {}): arg is T extends readonly any[] ? (unknown extends T ? never : readonly any[]) : any[];
-};
-
-declare const a: readonly string[] | string;
-declare const b: string[] | string;
-declare const c: unknown;
-
-if (MyArray.isArray(a)) {
-    a; // readonly string[]
-}
-else {
-    a;  // string
-}
-a; // readonly string[] | string;
-
-if (MyArray.isArray(b)) {
-    b; // string[] | string;
-}
-else {
-    b; // string
-}
-b; // string[] | string;
-
-if (MyArray.isArray(c)) {
-    c; // any[]
-}
-
-
-function f<T>(x: T) {
-    const a: readonly T[] | string = null!;
-    const b: T[] | string = null!;
-    const c: T = null!;
-
-    if (MyArray.isArray(a)) {
-        a; // readonly T[]
-    }
-    else {
-        a; // string
-    }
-    a; // readonly T[] | string;
-
-    if (MyArray.isArray(b)) {
-        b; // T[]
-    }
-    else {
-        b; // string
-    }
-    b;
-
-    if (MyArray.isArray(c)) {
-        c; // T & (T extends readonly any[] ? readonly any[] : any[])
-    }
-}
-
-
-//// [consistentUnionSubtypeReduction.js]
-// https://github.com/microsoft/TypeScript/issues/31155
-if (MyArray.isArray(a)) {
-    a; // readonly string[]
-}
-else {
-    a; // string
-}
-a; // readonly string[] | string;
-if (MyArray.isArray(b)) {
-    b; // string[] | string;
-}
-else {
-    b; // string
-}
-b; // string[] | string;
-if (MyArray.isArray(c)) {
-    c; // any[]
-}
-function f(x) {
-    var a = null;
-    var b = null;
-    var c = null;
-    if (MyArray.isArray(a)) {
-        a; // readonly T[]
-    }
-    else {
-        a; // string
-    }
-    a; // readonly T[] | string;
-    if (MyArray.isArray(b)) {
-        b; // T[]
-    }
-    else {
-        b; // string
-    }
-    b;
-    if (MyArray.isArray(c)) {
-        c; // T & (T extends readonly any[] ? readonly any[] : any[])
-    }
-}
diff --git a/tests/baselines/reference/consistentUnionSubtypeReduction.symbols b/tests/baselines/reference/consistentUnionSubtypeReduction.symbols
deleted file mode 100644
index 44333b25cf617..0000000000000
--- a/tests/baselines/reference/consistentUnionSubtypeReduction.symbols
+++ /dev/null
@@ -1,130 +0,0 @@
-=== tests/cases/compiler/consistentUnionSubtypeReduction.ts ===
-// https://github.com/microsoft/TypeScript/issues/31155
-
-declare const MyArray: {
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
-
-    isArray<T>(arg: T | {}): arg is T extends readonly any[] ? (unknown extends T ? never : readonly any[]) : any[];
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 3, 12))
->arg : Symbol(arg, Decl(consistentUnionSubtypeReduction.ts, 3, 15))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 3, 12))
->arg : Symbol(arg, Decl(consistentUnionSubtypeReduction.ts, 3, 15))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 3, 12))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 3, 12))
-
-};
-
-declare const a: readonly string[] | string;
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 6, 13))
-
-declare const b: string[] | string;
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 7, 13))
-
-declare const c: unknown;
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 8, 13))
-
-if (MyArray.isArray(a)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 6, 13))
-
-    a; // readonly string[]
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 6, 13))
-}
-else {
-    a;  // string
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 6, 13))
-}
-a; // readonly string[] | string;
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 6, 13))
-
-if (MyArray.isArray(b)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 7, 13))
-
-    b; // string[] | string;
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 7, 13))
-}
-else {
-    b; // string
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 7, 13))
-}
-b; // string[] | string;
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 7, 13))
-
-if (MyArray.isArray(c)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 8, 13))
-
-    c; // any[]
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 8, 13))
-}
-
-
-function f<T>(x: T) {
->f : Symbol(f, Decl(consistentUnionSubtypeReduction.ts, 28, 1))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 31, 11))
->x : Symbol(x, Decl(consistentUnionSubtypeReduction.ts, 31, 14))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 31, 11))
-
-    const a: readonly T[] | string = null!;
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 32, 9))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 31, 11))
-
-    const b: T[] | string = null!;
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 33, 9))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 31, 11))
-
-    const c: T = null!;
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 34, 9))
->T : Symbol(T, Decl(consistentUnionSubtypeReduction.ts, 31, 11))
-
-    if (MyArray.isArray(a)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 32, 9))
-
-        a; // readonly T[]
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 32, 9))
-    }
-    else {
-        a; // string
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 32, 9))
-    }
-    a; // readonly T[] | string;
->a : Symbol(a, Decl(consistentUnionSubtypeReduction.ts, 32, 9))
-
-    if (MyArray.isArray(b)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 33, 9))
-
-        b; // T[]
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 33, 9))
-    }
-    else {
-        b; // string
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 33, 9))
-    }
-    b;
->b : Symbol(b, Decl(consistentUnionSubtypeReduction.ts, 33, 9))
-
-    if (MyArray.isArray(c)) {
->MyArray.isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->MyArray : Symbol(MyArray, Decl(consistentUnionSubtypeReduction.ts, 2, 13))
->isArray : Symbol(isArray, Decl(consistentUnionSubtypeReduction.ts, 2, 24))
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 34, 9))
-
-        c; // T & (T extends readonly any[] ? readonly any[] : any[])
->c : Symbol(c, Decl(consistentUnionSubtypeReduction.ts, 34, 9))
-    }
-}
-
diff --git a/tests/baselines/reference/consistentUnionSubtypeReduction.types b/tests/baselines/reference/consistentUnionSubtypeReduction.types
deleted file mode 100644
index 059fb51b16cda..0000000000000
--- a/tests/baselines/reference/consistentUnionSubtypeReduction.types
+++ /dev/null
@@ -1,132 +0,0 @@
-=== tests/cases/compiler/consistentUnionSubtypeReduction.ts ===
-// https://github.com/microsoft/TypeScript/issues/31155
-
-declare const MyArray: {
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
-
-    isArray<T>(arg: T | {}): arg is T extends readonly any[] ? (unknown extends T ? never : readonly any[]) : any[];
->isArray : <T>(arg: T | {}) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->arg : {} | T
-
-};
-
-declare const a: readonly string[] | string;
->a : string | readonly string[]
-
-declare const b: string[] | string;
->b : string | string[]
-
-declare const c: unknown;
->c : unknown
-
-if (MyArray.isArray(a)) {
->MyArray.isArray(a) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->a : string | readonly string[]
-
-    a; // readonly string[]
->a : readonly string[]
-}
-else {
-    a;  // string
->a : string
-}
-a; // readonly string[] | string;
->a : string | readonly string[]
-
-if (MyArray.isArray(b)) {
->MyArray.isArray(b) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->b : string | string[]
-
-    b; // string[] | string;
->b : string[]
-}
-else {
-    b; // string
->b : string
-}
-b; // string[] | string;
->b : string | string[]
-
-if (MyArray.isArray(c)) {
->MyArray.isArray(c) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->c : unknown
-
-    c; // any[]
->c : any[]
-}
-
-
-function f<T>(x: T) {
->f : <T>(x: T) => void
->x : T
-
-    const a: readonly T[] | string = null!;
->a : string | readonly T[]
->null! : null
->null : null
-
-    const b: T[] | string = null!;
->b : string | T[]
->null! : null
->null : null
-
-    const c: T = null!;
->c : T
->null! : null
->null : null
-
-    if (MyArray.isArray(a)) {
->MyArray.isArray(a) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->a : string | readonly T[]
-
-        a; // readonly T[]
->a : readonly T[]
-    }
-    else {
-        a; // string
->a : string
-    }
-    a; // readonly T[] | string;
->a : string | readonly T[]
-
-    if (MyArray.isArray(b)) {
->MyArray.isArray(b) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->b : string | T[]
-
-        b; // T[]
->b : T[]
-    }
-    else {
-        b; // string
->b : string
-    }
-    b;
->b : string | T[]
-
-    if (MyArray.isArray(c)) {
->MyArray.isArray(c) : boolean
->MyArray.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->MyArray : { isArray<T>(arg: {} | T): arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]; }
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
->c : T
-
-        c; // T & (T extends readonly any[] ? readonly any[] : any[])
->c : T & (T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[])
-    }
-}
-
diff --git a/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types b/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types
index 2501ef2882d18..7aff4276be765 100644
--- a/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types
+++ b/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types
@@ -67,9 +67,9 @@ export const updateIfChanged = <T>(t: T) => {
 >assign : { <T, U>(target: T, source: U): T & U; <T, U, V>(target: T, source1: U, source2: V): T & U & V; <T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
 >Array.isArray(u) ? [] : {} : undefined[] | {}
 >Array.isArray(u) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >u : U
 >[] : undefined[]
 >{} : {}
diff --git a/tests/baselines/reference/fixSignatureCaching.types b/tests/baselines/reference/fixSignatureCaching.types
index 8765e8fc310f4..cf367966c0260 100644
--- a/tests/baselines/reference/fixSignatureCaching.types
+++ b/tests/baselines/reference/fixSignatureCaching.types
@@ -1109,9 +1109,9 @@ define(function () {
 >Array : ArrayConstructor
 
         Array.isArray : function (value) { return Object.prototype.toString.call(value) === '[object Array]'; };
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >function (value) { return Object.prototype.toString.call(value) === '[object Array]'; } : (value: any) => boolean
 >value : any
 >Object.prototype.toString.call(value) === '[object Array]' : boolean
diff --git a/tests/baselines/reference/isArray.types b/tests/baselines/reference/isArray.types
index 2e70eca8fb188..bc452b12bef01 100644
--- a/tests/baselines/reference/isArray.types
+++ b/tests/baselines/reference/isArray.types
@@ -5,9 +5,9 @@ var maybeArray: number | number[];
 
 if (Array.isArray(maybeArray)) {
 >Array.isArray(maybeArray) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >maybeArray : number | number[]
 
     maybeArray.length; // OK
diff --git a/tests/baselines/reference/literalFreshnessPropagationOnNarrowing.types b/tests/baselines/reference/literalFreshnessPropagationOnNarrowing.types
index 51ee436e6dd34..8fb03bc413f30 100644
--- a/tests/baselines/reference/literalFreshnessPropagationOnNarrowing.types
+++ b/tests/baselines/reference/literalFreshnessPropagationOnNarrowing.types
@@ -66,9 +66,9 @@ function f2() {
 >a4 : string | false | (string | false)[]
 >Array.isArray(elOrA) ? elOrA : [elOrA] : (string | false)[]
 >Array.isArray(elOrA) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >elOrA : string | false | (string | false)[]
 >elOrA : (string | false)[]
 >[elOrA] : (string | false)[]
@@ -83,9 +83,9 @@ function f2() {
 >...Array.isArray(elOrA) ? elOrA : [elOrA] : string | false
 >Array.isArray(elOrA) ? elOrA : [elOrA] : (string | false)[]
 >Array.isArray(elOrA) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >elOrA : string | false | (string | false)[]
 >elOrA : (string | false)[]
 >[elOrA] : (string | false)[]
diff --git a/tests/baselines/reference/malformedTags.types b/tests/baselines/reference/malformedTags.types
index c5d63bfd3cb5a..c3af959586790 100644
--- a/tests/baselines/reference/malformedTags.types
+++ b/tests/baselines/reference/malformedTags.types
@@ -6,7 +6,7 @@
  */
 var isArray = Array.isArray;
 >isArray : Function
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 
diff --git a/tests/baselines/reference/noIterationTypeErrorsInCFA.types b/tests/baselines/reference/noIterationTypeErrorsInCFA.types
index a008015c7d756..9d0122627ffae 100644
--- a/tests/baselines/reference/noIterationTypeErrorsInCFA.types
+++ b/tests/baselines/reference/noIterationTypeErrorsInCFA.types
@@ -10,9 +10,9 @@ export function doRemove(dds: F | F[]) {
     if (!Array.isArray(dds)) {
 >!Array.isArray(dds) : boolean
 >Array.isArray(dds) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >dds : F | F[]
 
         dds = [dds]
diff --git a/tests/baselines/reference/parserharness.types b/tests/baselines/reference/parserharness.types
index f4af8d0d64b8d..4c047e08d9115 100644
--- a/tests/baselines/reference/parserharness.types
+++ b/tests/baselines/reference/parserharness.types
@@ -3068,13 +3068,13 @@ module Harness {
 >(Array.isArray && Array.isArray(arg)) || arg instanceof Array : boolean
 >(Array.isArray && Array.isArray(arg)) : boolean
 >Array.isArray && Array.isArray(arg) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >Array.isArray(arg) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >arg : any
 >arg instanceof Array : boolean
 >arg : any
diff --git a/tests/baselines/reference/partiallyDiscriminantedUnions.types b/tests/baselines/reference/partiallyDiscriminantedUnions.types
index c9afb116ca3e6..f1d44249c0eb2 100644
--- a/tests/baselines/reference/partiallyDiscriminantedUnions.types
+++ b/tests/baselines/reference/partiallyDiscriminantedUnions.types
@@ -77,9 +77,9 @@ function isShape(s : Shapes): s is Shape {
     return !Array.isArray(s);
 >!Array.isArray(s) : boolean
 >Array.isArray(s) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >s : Shapes
 }
 
diff --git a/tests/baselines/reference/spreadBooleanRespectsFreshness.types b/tests/baselines/reference/spreadBooleanRespectsFreshness.types
index 195582d79391a..cd20dc31944b6 100644
--- a/tests/baselines/reference/spreadBooleanRespectsFreshness.types
+++ b/tests/baselines/reference/spreadBooleanRespectsFreshness.types
@@ -22,9 +22,9 @@ foo1 = [...Array.isArray(foo2) ? foo2 : [foo2]];
 >...Array.isArray(foo2) ? foo2 : [foo2] : FooBase
 >Array.isArray(foo2) ? foo2 : [foo2] : FooArray
 >Array.isArray(foo2) : boolean
->Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array.isArray : (arg: any) => arg is any[]
 >Array : ArrayConstructor
->isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>isArray : (arg: any) => arg is any[]
 >foo2 : Foo
 >foo2 : FooArray
 >[foo2] : FooBase[]
diff --git a/tests/cases/compiler/consistentUnionSubtypeReduction.ts b/tests/cases/compiler/consistentUnionSubtypeReduction.ts
deleted file mode 100644
index 94fd44239a1c0..0000000000000
--- a/tests/cases/compiler/consistentUnionSubtypeReduction.ts
+++ /dev/null
@@ -1,56 +0,0 @@
-// https://github.com/microsoft/TypeScript/issues/31155
-
-declare const MyArray: {
-    isArray<T>(arg: T | {}): arg is T extends readonly any[] ? (unknown extends T ? never : readonly any[]) : any[];
-};
-
-declare const a: readonly string[] | string;
-declare const b: string[] | string;
-declare const c: unknown;
-
-if (MyArray.isArray(a)) {
-    a; // readonly string[]
-}
-else {
-    a;  // string
-}
-a; // readonly string[] | string;
-
-if (MyArray.isArray(b)) {
-    b; // string[] | string;
-}
-else {
-    b; // string
-}
-b; // string[] | string;
-
-if (MyArray.isArray(c)) {
-    c; // any[]
-}
-
-
-function f<T>(x: T) {
-    const a: readonly T[] | string = null!;
-    const b: T[] | string = null!;
-    const c: T = null!;
-
-    if (MyArray.isArray(a)) {
-        a; // readonly T[]
-    }
-    else {
-        a; // string
-    }
-    a; // readonly T[] | string;
-
-    if (MyArray.isArray(b)) {
-        b; // T[]
-    }
-    else {
-        b; // string
-    }
-    b;
-
-    if (MyArray.isArray(c)) {
-        c; // T & (T extends readonly any[] ? readonly any[] : any[])
-    }
-}