diff --git a/tests/baselines/reference/controlFlowInstanceof.js b/tests/baselines/reference/controlFlowInstanceof.js
index 7c7833927c..3f2287b462 100644
--- a/tests/baselines/reference/controlFlowInstanceof.js
+++ b/tests/baselines/reference/controlFlowInstanceof.js
@@ -77,6 +77,25 @@ function foo(x: A | undefined) {
         x;  // A
     }
     x;  // A
+}
+
+// X is neither assignable to Y nor a subtype of Y
+// Y is assignable to X, but not a subtype of X
+
+interface X {
+    x?: string;
+}
+
+class Y {
+    y: string;
+}
+
+function goo(x: X) {
+    x;
+    if (x instanceof Y) {
+        x.y;
+    }
+    x;
 }
 
 //// [controlFlowInstanceof.js]
@@ -154,3 +173,12 @@ function foo(x) {
     }
     x; // A
 }
+class Y {
+}
+function goo(x) {
+    x;
+    if (x instanceof Y) {
+        x.y;
+    }
+    x;
+}
diff --git a/tests/baselines/reference/controlFlowInstanceof.symbols b/tests/baselines/reference/controlFlowInstanceof.symbols
index 64b567c154..3189482799 100644
--- a/tests/baselines/reference/controlFlowInstanceof.symbols
+++ b/tests/baselines/reference/controlFlowInstanceof.symbols
@@ -192,3 +192,41 @@ function foo(x: A | undefined) {
     x;  // A
 >x : Symbol(x, Decl(controlFlowInstanceof.ts, 50, 13))
 }
+
+// X is neither assignable to Y nor a subtype of Y
+// Y is assignable to X, but not a subtype of X
+
+interface X {
+>X : Symbol(X, Decl(controlFlowInstanceof.ts, 78, 1))
+
+    x?: string;
+>x : Symbol(X.x, Decl(controlFlowInstanceof.ts, 83, 13))
+}
+
+class Y {
+>Y : Symbol(Y, Decl(controlFlowInstanceof.ts, 85, 1))
+
+    y: string;
+>y : Symbol(Y.y, Decl(controlFlowInstanceof.ts, 87, 9))
+}
+
+function goo(x: X) {
+>goo : Symbol(goo, Decl(controlFlowInstanceof.ts, 89, 1))
+>x : Symbol(x, Decl(controlFlowInstanceof.ts, 91, 13))
+>X : Symbol(X, Decl(controlFlowInstanceof.ts, 78, 1))
+
+    x;
+>x : Symbol(x, Decl(controlFlowInstanceof.ts, 91, 13))
+
+    if (x instanceof Y) {
+>x : Symbol(x, Decl(controlFlowInstanceof.ts, 91, 13))
+>Y : Symbol(Y, Decl(controlFlowInstanceof.ts, 85, 1))
+
+        x.y;
+>x.y : Symbol(Y.y, Decl(controlFlowInstanceof.ts, 87, 9))
+>x : Symbol(x, Decl(controlFlowInstanceof.ts, 91, 13))
+>y : Symbol(Y.y, Decl(controlFlowInstanceof.ts, 87, 9))
+    }
+    x;
+>x : Symbol(x, Decl(controlFlowInstanceof.ts, 91, 13))
+}
diff --git a/tests/baselines/reference/controlFlowInstanceof.types b/tests/baselines/reference/controlFlowInstanceof.types
index 362715914f..e52d1a25b1 100644
--- a/tests/baselines/reference/controlFlowInstanceof.types
+++ b/tests/baselines/reference/controlFlowInstanceof.types
@@ -215,3 +215,42 @@ function foo(x: A | undefined) {
     x;  // A
 >x : A
 }
+
+// X is neither assignable to Y nor a subtype of Y
+// Y is assignable to X, but not a subtype of X
+
+interface X {
+>X : X
+
+    x?: string;
+>x : string
+}
+
+class Y {
+>Y : Y
+
+    y: string;
+>y : string
+}
+
+function goo(x: X) {
+>goo : (x: X) => void
+>x : X
+>X : X
+
+    x;
+>x : X
+
+    if (x instanceof Y) {
+>x instanceof Y : boolean
+>x : X
+>Y : typeof Y
+
+        x.y;
+>x.y : string
+>x : Y
+>y : string
+    }
+    x;
+>x : X
+}
diff --git a/tests/baselines/reference/discriminantsAndTypePredicates.js b/tests/baselines/reference/discriminantsAndTypePredicates.js
new file mode 100644
index 0000000000..66cfe056ab
--- /dev/null
+++ b/tests/baselines/reference/discriminantsAndTypePredicates.js
@@ -0,0 +1,59 @@
+//// [discriminantsAndTypePredicates.ts]
+// Repro from #10145
+
+interface A { type: 'A' }
+interface B { type: 'B' }
+
+function isA(x: A | B): x is A { return x.type === 'A'; }
+function isB(x: A | B): x is B { return x.type === 'B'; }
+
+function foo1(x: A | B): any {
+    x;  // A | B
+    if (isA(x)) {
+        return x;  // A
+    }
+    x;  // B
+    if (isB(x)) {
+        return x;  // B
+    }
+    x;  // never
+}
+
+function foo2(x: A | B): any {
+    x;  // A | B
+    if (x.type === 'A') {
+        return x;  // A
+    }
+    x;  // B
+    if (x.type === 'B') {
+        return x;  // B
+    }
+    x;  // never
+}
+
+//// [discriminantsAndTypePredicates.js]
+// Repro from #10145
+function isA(x) { return x.type === 'A'; }
+function isB(x) { return x.type === 'B'; }
+function foo1(x) {
+    x; // A | B
+    if (isA(x)) {
+        return x; // A
+    }
+    x; // B
+    if (isB(x)) {
+        return x; // B
+    }
+    x; // never
+}
+function foo2(x) {
+    x; // A | B
+    if (x.type === 'A') {
+        return x; // A
+    }
+    x; // B
+    if (x.type === 'B') {
+        return x; // B
+    }
+    x; // never
+}
diff --git a/tests/baselines/reference/discriminantsAndTypePredicates.symbols b/tests/baselines/reference/discriminantsAndTypePredicates.symbols
new file mode 100644
index 0000000000..4f41282393
--- /dev/null
+++ b/tests/baselines/reference/discriminantsAndTypePredicates.symbols
@@ -0,0 +1,94 @@
+=== tests/cases/compiler/discriminantsAndTypePredicates.ts ===
+// Repro from #10145
+
+interface A { type: 'A' }
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>type : Symbol(A.type, Decl(discriminantsAndTypePredicates.ts, 2, 13))
+
+interface B { type: 'B' }
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+>type : Symbol(B.type, Decl(discriminantsAndTypePredicates.ts, 3, 13))
+
+function isA(x: A | B): x is A { return x.type === 'A'; }
+>isA : Symbol(isA, Decl(discriminantsAndTypePredicates.ts, 3, 25))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 5, 13))
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 5, 13))
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>x.type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 5, 13))
+>type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+
+function isB(x: A | B): x is B { return x.type === 'B'; }
+>isB : Symbol(isB, Decl(discriminantsAndTypePredicates.ts, 5, 57))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 6, 13))
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 6, 13))
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+>x.type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 6, 13))
+>type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+
+function foo1(x: A | B): any {
+>foo1 : Symbol(foo1, Decl(discriminantsAndTypePredicates.ts, 6, 57))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+
+    x;  // A | B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+
+    if (isA(x)) {
+>isA : Symbol(isA, Decl(discriminantsAndTypePredicates.ts, 3, 25))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+
+        return x;  // A
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+    }
+    x;  // B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+
+    if (isB(x)) {
+>isB : Symbol(isB, Decl(discriminantsAndTypePredicates.ts, 5, 57))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+
+        return x;  // B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+    }
+    x;  // never
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 8, 14))
+}
+
+function foo2(x: A | B): any {
+>foo2 : Symbol(foo2, Decl(discriminantsAndTypePredicates.ts, 18, 1))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+>A : Symbol(A, Decl(discriminantsAndTypePredicates.ts, 0, 0))
+>B : Symbol(B, Decl(discriminantsAndTypePredicates.ts, 2, 25))
+
+    x;  // A | B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+
+    if (x.type === 'A') {
+>x.type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+>type : Symbol(type, Decl(discriminantsAndTypePredicates.ts, 2, 13), Decl(discriminantsAndTypePredicates.ts, 3, 13))
+
+        return x;  // A
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+    }
+    x;  // B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+
+    if (x.type === 'B') {
+>x.type : Symbol(B.type, Decl(discriminantsAndTypePredicates.ts, 3, 13))
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+>type : Symbol(B.type, Decl(discriminantsAndTypePredicates.ts, 3, 13))
+
+        return x;  // B
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+    }
+    x;  // never
+>x : Symbol(x, Decl(discriminantsAndTypePredicates.ts, 20, 14))
+}
diff --git a/tests/baselines/reference/discriminantsAndTypePredicates.types b/tests/baselines/reference/discriminantsAndTypePredicates.types
new file mode 100644
index 0000000000..f7675b1475
--- /dev/null
+++ b/tests/baselines/reference/discriminantsAndTypePredicates.types
@@ -0,0 +1,104 @@
+=== tests/cases/compiler/discriminantsAndTypePredicates.ts ===
+// Repro from #10145
+
+interface A { type: 'A' }
+>A : A
+>type : "A"
+
+interface B { type: 'B' }
+>B : B
+>type : "B"
+
+function isA(x: A | B): x is A { return x.type === 'A'; }
+>isA : (x: A | B) => x is A
+>x : A | B
+>A : A
+>B : B
+>x : any
+>A : A
+>x.type === 'A' : boolean
+>x.type : "A" | "B"
+>x : A | B
+>type : "A" | "B"
+>'A' : "A"
+
+function isB(x: A | B): x is B { return x.type === 'B'; }
+>isB : (x: A | B) => x is B
+>x : A | B
+>A : A
+>B : B
+>x : any
+>B : B
+>x.type === 'B' : boolean
+>x.type : "A" | "B"
+>x : A | B
+>type : "A" | "B"
+>'B' : "B"
+
+function foo1(x: A | B): any {
+>foo1 : (x: A | B) => any
+>x : A | B
+>A : A
+>B : B
+
+    x;  // A | B
+>x : A | B
+
+    if (isA(x)) {
+>isA(x) : boolean
+>isA : (x: A | B) => x is A
+>x : A | B
+
+        return x;  // A
+>x : A
+    }
+    x;  // B
+>x : B
+
+    if (isB(x)) {
+>isB(x) : boolean
+>isB : (x: A | B) => x is B
+>x : B
+
+        return x;  // B
+>x : B
+    }
+    x;  // never
+>x : never
+}
+
+function foo2(x: A | B): any {
+>foo2 : (x: A | B) => any
+>x : A | B
+>A : A
+>B : B
+
+    x;  // A | B
+>x : A | B
+
+    if (x.type === 'A') {
+>x.type === 'A' : boolean
+>x.type : "A" | "B"
+>x : A | B
+>type : "A" | "B"
+>'A' : "A"
+
+        return x;  // A
+>x : A
+    }
+    x;  // B
+>x : B
+
+    if (x.type === 'B') {
+>x.type === 'B' : boolean
+>x.type : "B"
+>x : B
+>type : "B"
+>'B' : "B"
+
+        return x;  // B
+>x : B
+    }
+    x;  // never
+>x : never
+}