diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 01c8ef4f34..26a2e9fbc7 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8529,6 +8529,15 @@ namespace ts {
             return binarySearch(types, type, getTypeId, compareValues) >= 0;
         }
 
+        function insertType(types: Type[], type: Type): boolean {
+            const index = binarySearch(types, type, getTypeId, compareValues);
+            if (index < 0) {
+                types.splice(~index, 0, type);
+                return true;
+            }
+            return false;
+        }
+
         // Return true if the given intersection type contains
         // more than one unit type or,
         // an object type and a nullable type (null or undefined), or
@@ -8696,7 +8705,7 @@ namespace ts {
                     includes & TypeFlags.Undefined ? includes & TypeFlags.NonWideningType ? undefinedType : undefinedWideningType :
                         neverType;
             }
-            return getUnionTypeFromSortedList(typeSet, includes & TypeFlags.NotUnit ? 0 : TypeFlags.UnionOfUnitTypes, aliasSymbol, aliasTypeArguments);
+            return getUnionTypeFromSortedList(typeSet, includes & TypeFlags.NotPrimitiveUnion ? 0 : TypeFlags.UnionOfPrimitiveTypes, aliasSymbol, aliasTypeArguments);
         }
 
         function getUnionTypePredicate(signatures: ReadonlyArray<Signature>): TypePredicate | undefined {
@@ -8819,26 +8828,63 @@ namespace ts {
             }
         }
 
-        // When intersecting unions of unit types we can simply intersect based on type identity.
-        // Here we remove all unions of unit types from the given list and replace them with a
-        // a single union containing an intersection of the unit types.
-        function intersectUnionsOfUnitTypes(types: Type[]) {
-            const unionIndex = findIndex(types, t => (t.flags & TypeFlags.UnionOfUnitTypes) !== 0);
-            const unionType = <UnionType>types[unionIndex];
-            let intersection = unionType.types;
-            let i = types.length - 1;
-            while (i > unionIndex) {
+        // Check that the given type has a match in every union. A given type is matched by
+        // an identical type, and a literal type is additionally matched by its corresponding
+        // primitive type.
+        function eachUnionContains(unionTypes: UnionType[], type: Type) {
+            for (const u of unionTypes) {
+                if (!containsType(u.types, type)) {
+                    const primitive = type.flags & TypeFlags.StringLiteral ? stringType :
+                        type.flags & TypeFlags.NumberLiteral ? numberType :
+                        type.flags & TypeFlags.UniqueESSymbol ? esSymbolType :
+                        undefined;
+                    if (!primitive || !containsType(u.types, primitive)) {
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+
+        // If the given list of types contains more than one union of primitive types, replace the
+        // first with a union containing an intersection of those primitive types, then remove the
+        // other unions and return true. Otherwise, do nothing and return false.
+        function intersectUnionsOfPrimitiveTypes(types: Type[]) {
+            let unionTypes: UnionType[] | undefined;
+            const index = findIndex(types, t => (t.flags & TypeFlags.UnionOfPrimitiveTypes) !== 0);
+            let i = index + 1;
+            // Remove all but the first union of primitive types and collect them in
+            // the unionTypes array.
+            while (i < types.length) {
                 const t = types[i];
-                if (t.flags & TypeFlags.UnionOfUnitTypes) {
-                    intersection = filter(intersection, u => containsType((<UnionType>t).types, u));
+                if (t.flags & TypeFlags.UnionOfPrimitiveTypes) {
+                    (unionTypes || (unionTypes = [<UnionType>types[index]])).push(<UnionType>t);
                     orderedRemoveItemAt(types, i);
                 }
-                i--;
+                else {
+                    i++;
+                }
             }
-            if (intersection === unionType.types) {
+            // Return false if there was only one union of primitive types
+            if (!unionTypes) {
                 return false;
             }
-            types[unionIndex] = getUnionTypeFromSortedList(intersection, unionType.flags & TypeFlags.UnionOfUnitTypes);
+            // We have more than one union of primitive types, now intersect them. For each
+            // type in each union we check if the type is matched in every union and if so
+            // we include it in the result.
+            const checked: Type[] = [];
+            const result: Type[] = [];
+            for (const u of unionTypes) {
+                for (const t of u.types) {
+                    if (insertType(checked, t)) {
+                        if (eachUnionContains(unionTypes, t)) {
+                            insertType(result, t);
+                        }
+                    }
+                }
+            }
+            // Finally replace the first union with the result
+            types[index] = getUnionTypeFromSortedList(result, TypeFlags.UnionOfPrimitiveTypes);
             return true;
         }
 
@@ -8879,7 +8925,7 @@ namespace ts {
                 return typeSet[0];
             }
             if (includes & TypeFlags.Union) {
-                if (includes & TypeFlags.UnionOfUnitTypes && intersectUnionsOfUnitTypes(typeSet)) {
+                if (includes & TypeFlags.UnionOfPrimitiveTypes && intersectUnionsOfPrimitiveTypes(typeSet)) {
                     // When the intersection creates a reduced set (which might mean that *all* union types have
                     // disappeared), we restart the operation to get a new set of combined flags. Once we have
                     // reduced we'll never reduce again, so this occurs at most once.
@@ -13976,7 +14022,7 @@ namespace ts {
             if (type.flags & TypeFlags.Union) {
                 const types = (<UnionType>type).types;
                 const filtered = filter(types, f);
-                return filtered === types ? type : getUnionTypeFromSortedList(filtered, type.flags & TypeFlags.UnionOfUnitTypes);
+                return filtered === types ? type : getUnionTypeFromSortedList(filtered, type.flags & TypeFlags.UnionOfPrimitiveTypes);
             }
             return f(type) ? type : neverType;
         }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 87664652b3..e1f5dcfa4e 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3675,7 +3675,7 @@ namespace ts {
         /* @internal */
         FreshLiteral            = 1 << 25,  // Fresh literal or unique type
         /* @internal */
-        UnionOfUnitTypes        = 1 << 26,  // Type is union of unit types
+        UnionOfPrimitiveTypes   = 1 << 26,  // Type is union of primitive types
         /* @internal */
         ContainsWideningType    = 1 << 27,  // Type is or contains undefined or null widening type
         /* @internal */
@@ -3720,7 +3720,7 @@ namespace ts {
         Narrowable = Any | Unknown | StructuredOrInstantiable | StringLike | NumberLike | BooleanLike | ESSymbol | UniqueESSymbol | NonPrimitive,
         NotUnionOrUnit = Any | Unknown | ESSymbol | Object | NonPrimitive,
         /* @internal */
-        NotUnit = Any | String | Number | Boolean | Enum | ESSymbol | Void | Never | StructuredOrInstantiable,
+        NotPrimitiveUnion = Any | Unknown | Enum | Void | Never | StructuredOrInstantiable,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectLiteral,
         /* @internal */
diff --git a/tests/baselines/reference/intersectionsOfLargeUnions2.errors.txt b/tests/baselines/reference/intersectionsOfLargeUnions2.errors.txt
new file mode 100644
index 0000000000..664569582b
--- /dev/null
+++ b/tests/baselines/reference/intersectionsOfLargeUnions2.errors.txt
@@ -0,0 +1,45 @@
+tests/cases/compiler/intersectionsOfLargeUnions2.ts(31,15): error TS2536: Type 'T' cannot be used to index type 'HTMLElementTagNameMap'.
+tests/cases/compiler/intersectionsOfLargeUnions2.ts(31,15): error TS2536: Type 'P' cannot be used to index type 'HTMLElementTagNameMap[T]'.
+
+
+==== tests/cases/compiler/intersectionsOfLargeUnions2.ts (2 errors) ====
+    // Repro from #24233
+    
+    declare global {
+        interface ElementTagNameMap {
+            [index: number]: HTMLElement
+        }
+    
+        interface HTMLElement {
+            [index: number]: HTMLElement;
+        }
+    }
+    
+    export function assertIsElement(node: Node | null): node is Element {
+        let nodeType = node === null ? null : node.nodeType;
+        return nodeType === 1;
+    }
+      
+    export function assertNodeTagName<
+        T extends keyof ElementTagNameMap,
+        U extends ElementTagNameMap[T]>(node: Node | null, tagName: T): node is U {
+        if (assertIsElement(node)) {
+            const nodeTagName = node.tagName.toLowerCase();
+             return nodeTagName === tagName;
+        }
+        return false;
+    }
+      
+    export function assertNodeProperty<
+        T extends keyof ElementTagNameMap,
+        P extends keyof ElementTagNameMap[T],
+        V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) {
+                  ~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2536: Type 'T' cannot be used to index type 'HTMLElementTagNameMap'.
+                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2536: Type 'P' cannot be used to index type 'HTMLElementTagNameMap[T]'.
+        if (assertNodeTagName(node, tagName)) {
+            node[prop];
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/intersectionsOfLargeUnions2.js b/tests/baselines/reference/intersectionsOfLargeUnions2.js
new file mode 100644
index 0000000000..80add6cd5c
--- /dev/null
+++ b/tests/baselines/reference/intersectionsOfLargeUnions2.js
@@ -0,0 +1,61 @@
+//// [intersectionsOfLargeUnions2.ts]
+// Repro from #24233
+
+declare global {
+    interface ElementTagNameMap {
+        [index: number]: HTMLElement
+    }
+
+    interface HTMLElement {
+        [index: number]: HTMLElement;
+    }
+}
+
+export function assertIsElement(node: Node | null): node is Element {
+    let nodeType = node === null ? null : node.nodeType;
+    return nodeType === 1;
+}
+  
+export function assertNodeTagName<
+    T extends keyof ElementTagNameMap,
+    U extends ElementTagNameMap[T]>(node: Node | null, tagName: T): node is U {
+    if (assertIsElement(node)) {
+        const nodeTagName = node.tagName.toLowerCase();
+         return nodeTagName === tagName;
+    }
+    return false;
+}
+  
+export function assertNodeProperty<
+    T extends keyof ElementTagNameMap,
+    P extends keyof ElementTagNameMap[T],
+    V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) {
+    if (assertNodeTagName(node, tagName)) {
+        node[prop];
+    }
+}
+
+
+//// [intersectionsOfLargeUnions2.js]
+"use strict";
+// Repro from #24233
+exports.__esModule = true;
+function assertIsElement(node) {
+    var nodeType = node === null ? null : node.nodeType;
+    return nodeType === 1;
+}
+exports.assertIsElement = assertIsElement;
+function assertNodeTagName(node, tagName) {
+    if (assertIsElement(node)) {
+        var nodeTagName = node.tagName.toLowerCase();
+        return nodeTagName === tagName;
+    }
+    return false;
+}
+exports.assertNodeTagName = assertNodeTagName;
+function assertNodeProperty(node, tagName, prop, value) {
+    if (assertNodeTagName(node, tagName)) {
+        node[prop];
+    }
+}
+exports.assertNodeProperty = assertNodeProperty;
diff --git a/tests/baselines/reference/intersectionsOfLargeUnions2.symbols b/tests/baselines/reference/intersectionsOfLargeUnions2.symbols
new file mode 100644
index 0000000000..fc2ea00402
--- /dev/null
+++ b/tests/baselines/reference/intersectionsOfLargeUnions2.symbols
@@ -0,0 +1,115 @@
+=== tests/cases/compiler/intersectionsOfLargeUnions2.ts ===
+// Repro from #24233
+
+declare global {
+>global : Symbol(global, Decl(intersectionsOfLargeUnions2.ts, 0, 0))
+
+    interface ElementTagNameMap {
+>ElementTagNameMap : Symbol(ElementTagNameMap, Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 2, 16))
+
+        [index: number]: HTMLElement
+>index : Symbol(index, Decl(intersectionsOfLargeUnions2.ts, 4, 9))
+>HTMLElement : Symbol(HTMLElement, Decl(intersectionsOfLargeUnions2.ts, 5, 5))
+    }
+
+    interface HTMLElement {
+>HTMLElement : Symbol(HTMLElement, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 5, 5))
+
+        [index: number]: HTMLElement;
+>index : Symbol(index, Decl(intersectionsOfLargeUnions2.ts, 8, 9))
+>HTMLElement : Symbol(HTMLElement, Decl(intersectionsOfLargeUnions2.ts, 5, 5))
+    }
+}
+
+export function assertIsElement(node: Node | null): node is Element {
+>assertIsElement : Symbol(assertIsElement, Decl(intersectionsOfLargeUnions2.ts, 10, 1))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 12, 32))
+>Node : Symbol(Node, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 12, 32))
+>Element : Symbol(Element, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+
+    let nodeType = node === null ? null : node.nodeType;
+>nodeType : Symbol(nodeType, Decl(intersectionsOfLargeUnions2.ts, 13, 7))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 12, 32))
+>node.nodeType : Symbol(Node.nodeType, Decl(lib.dom.d.ts, --, --))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 12, 32))
+>nodeType : Symbol(Node.nodeType, Decl(lib.dom.d.ts, --, --))
+
+    return nodeType === 1;
+>nodeType : Symbol(nodeType, Decl(intersectionsOfLargeUnions2.ts, 13, 7))
+}
+  
+export function assertNodeTagName<
+>assertNodeTagName : Symbol(assertNodeTagName, Decl(intersectionsOfLargeUnions2.ts, 15, 1))
+
+    T extends keyof ElementTagNameMap,
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 17, 34))
+>ElementTagNameMap : Symbol(ElementTagNameMap, Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 2, 16))
+
+    U extends ElementTagNameMap[T]>(node: Node | null, tagName: T): node is U {
+>U : Symbol(U, Decl(intersectionsOfLargeUnions2.ts, 18, 38))
+>ElementTagNameMap : Symbol(ElementTagNameMap, Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 2, 16))
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 17, 34))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 19, 36))
+>Node : Symbol(Node, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+>tagName : Symbol(tagName, Decl(intersectionsOfLargeUnions2.ts, 19, 54))
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 17, 34))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 19, 36))
+>U : Symbol(U, Decl(intersectionsOfLargeUnions2.ts, 18, 38))
+
+    if (assertIsElement(node)) {
+>assertIsElement : Symbol(assertIsElement, Decl(intersectionsOfLargeUnions2.ts, 10, 1))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 19, 36))
+
+        const nodeTagName = node.tagName.toLowerCase();
+>nodeTagName : Symbol(nodeTagName, Decl(intersectionsOfLargeUnions2.ts, 21, 13))
+>node.tagName.toLowerCase : Symbol(String.toLowerCase, Decl(lib.es5.d.ts, --, --))
+>node.tagName : Symbol(Element.tagName, Decl(lib.dom.d.ts, --, --))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 19, 36))
+>tagName : Symbol(Element.tagName, Decl(lib.dom.d.ts, --, --))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.es5.d.ts, --, --))
+
+         return nodeTagName === tagName;
+>nodeTagName : Symbol(nodeTagName, Decl(intersectionsOfLargeUnions2.ts, 21, 13))
+>tagName : Symbol(tagName, Decl(intersectionsOfLargeUnions2.ts, 19, 54))
+    }
+    return false;
+}
+  
+export function assertNodeProperty<
+>assertNodeProperty : Symbol(assertNodeProperty, Decl(intersectionsOfLargeUnions2.ts, 25, 1))
+
+    T extends keyof ElementTagNameMap,
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 27, 35))
+>ElementTagNameMap : Symbol(ElementTagNameMap, Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 2, 16))
+
+    P extends keyof ElementTagNameMap[T],
+>P : Symbol(P, Decl(intersectionsOfLargeUnions2.ts, 28, 38))
+>ElementTagNameMap : Symbol(ElementTagNameMap, Decl(lib.dom.d.ts, --, --), Decl(intersectionsOfLargeUnions2.ts, 2, 16))
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 27, 35))
+
+    V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) {
+>V : Symbol(V, Decl(intersectionsOfLargeUnions2.ts, 29, 41))
+>HTMLElementTagNameMap : Symbol(HTMLElementTagNameMap, Decl(lib.dom.d.ts, --, --))
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 27, 35))
+>P : Symbol(P, Decl(intersectionsOfLargeUnions2.ts, 28, 38))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 30, 43))
+>Node : Symbol(Node, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+>tagName : Symbol(tagName, Decl(intersectionsOfLargeUnions2.ts, 30, 61))
+>T : Symbol(T, Decl(intersectionsOfLargeUnions2.ts, 27, 35))
+>prop : Symbol(prop, Decl(intersectionsOfLargeUnions2.ts, 30, 73))
+>P : Symbol(P, Decl(intersectionsOfLargeUnions2.ts, 28, 38))
+>value : Symbol(value, Decl(intersectionsOfLargeUnions2.ts, 30, 82))
+>V : Symbol(V, Decl(intersectionsOfLargeUnions2.ts, 29, 41))
+
+    if (assertNodeTagName(node, tagName)) {
+>assertNodeTagName : Symbol(assertNodeTagName, Decl(intersectionsOfLargeUnions2.ts, 15, 1))
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 30, 43))
+>tagName : Symbol(tagName, Decl(intersectionsOfLargeUnions2.ts, 30, 61))
+
+        node[prop];
+>node : Symbol(node, Decl(intersectionsOfLargeUnions2.ts, 30, 43))
+>prop : Symbol(prop, Decl(intersectionsOfLargeUnions2.ts, 30, 73))
+    }
+}
+
diff --git a/tests/baselines/reference/intersectionsOfLargeUnions2.types b/tests/baselines/reference/intersectionsOfLargeUnions2.types
new file mode 100644
index 0000000000..92edecd325
--- /dev/null
+++ b/tests/baselines/reference/intersectionsOfLargeUnions2.types
@@ -0,0 +1,130 @@
+=== tests/cases/compiler/intersectionsOfLargeUnions2.ts ===
+// Repro from #24233
+
+declare global {
+>global : any
+
+    interface ElementTagNameMap {
+>ElementTagNameMap : ElementTagNameMap
+
+        [index: number]: HTMLElement
+>index : number
+>HTMLElement : global.HTMLElement
+    }
+
+    interface HTMLElement {
+>HTMLElement : HTMLElement
+
+        [index: number]: HTMLElement;
+>index : number
+>HTMLElement : global.HTMLElement
+    }
+}
+
+export function assertIsElement(node: Node | null): node is Element {
+>assertIsElement : (node: Node | null) => node is Element
+>node : Node | null
+>Node : Node
+>null : null
+>node : any
+>Element : Element
+
+    let nodeType = node === null ? null : node.nodeType;
+>nodeType : number | null
+>node === null ? null : node.nodeType : number | null
+>node === null : boolean
+>node : Node | null
+>null : null
+>null : null
+>node.nodeType : number
+>node : Node
+>nodeType : number
+
+    return nodeType === 1;
+>nodeType === 1 : boolean
+>nodeType : number | null
+>1 : 1
+}
+  
+export function assertNodeTagName<
+>assertNodeTagName : <T extends number | "symbol" | "object" | "a" | "abbr" | "acronym" | "address" | "applet" | "area" | "article" | "aside" | "audio" | "b" | "base" | "basefont" | "bdo" | "big" | "blockquote" | "body" | "br" | "button" | "canvas" | "caption" | "center" | "cite" | "code" | "col" | "colgroup" | "data" | "datalist" | "dd" | "del" | "dfn" | "dir" | "div" | "dl" | "dt" | "em" | "embed" | "fieldset" | "figcaption" | "figure" | "font" | "footer" | "form" | "frame" | "frameset" | "h1" | "h2" | "h3" | "h4" | "h5" | "h6" | "head" | "header" | "hgroup" | "hr" | "html" | "i" | "iframe" | "img" | "input" | "ins" | "isindex" | "kbd" | "keygen" | "label" | "legend" | "li" | "link" | "listing" | "map" | "mark" | "marquee" | "menu" | "meta" | "meter" | "nav" | "nextid" | "nobr" | "noframes" | "noscript" | "ol" | "optgroup" | "option" | "output" | "p" | "param" | "picture" | "plaintext" | "pre" | "progress" | "q" | "rt" | "ruby" | "s" | "samp" | "script" | "section" | "select" | "slot" | "small" | "source" | "span" | "strike" | "strong" | "style" | "sub" | "sup" | "table" | "tbody" | "td" | "template" | "textarea" | "tfoot" | "th" | "thead" | "time" | "title" | "tr" | "track" | "tt" | "u" | "ul" | "var" | "video" | "wbr" | "xmp" | "circle" | "clipPath" | "defs" | "desc" | "ellipse" | "feBlend" | "feColorMatrix" | "feComponentTransfer" | "feComposite" | "feConvolveMatrix" | "feDiffuseLighting" | "feDisplacementMap" | "feDistantLight" | "feFlood" | "feFuncA" | "feFuncB" | "feFuncG" | "feFuncR" | "feGaussianBlur" | "feImage" | "feMerge" | "feMergeNode" | "feMorphology" | "feOffset" | "fePointLight" | "feSpecularLighting" | "feSpotLight" | "feTile" | "feTurbulence" | "filter" | "foreignObject" | "g" | "image" | "line" | "linearGradient" | "marker" | "mask" | "metadata" | "path" | "pattern" | "polygon" | "polyline" | "radialGradient" | "rect" | "stop" | "svg" | "switch" | "text" | "textPath" | "tspan" | "use" | "view", U extends ElementTagNameMap[T]>(node: Node | null, tagName: T) => node is U
+
+    T extends keyof ElementTagNameMap,
+>T : T
+>ElementTagNameMap : ElementTagNameMap
+
+    U extends ElementTagNameMap[T]>(node: Node | null, tagName: T): node is U {
+>U : U
+>ElementTagNameMap : ElementTagNameMap
+>T : T
+>node : Node | null
+>Node : Node
+>null : null
+>tagName : T
+>T : T
+>node : any
+>U : U
+
+    if (assertIsElement(node)) {
+>assertIsElement(node) : boolean
+>assertIsElement : (node: Node | null) => node is Element
+>node : Node | null
+
+        const nodeTagName = node.tagName.toLowerCase();
+>nodeTagName : string
+>node.tagName.toLowerCase() : string
+>node.tagName.toLowerCase : () => string
+>node.tagName : string
+>node : Element
+>tagName : string
+>toLowerCase : () => string
+
+         return nodeTagName === tagName;
+>nodeTagName === tagName : boolean
+>nodeTagName : string
+>tagName : T
+    }
+    return false;
+>false : false
+}
+  
+export function assertNodeProperty<
+>assertNodeProperty : <T extends number | "symbol" | "object" | "a" | "abbr" | "acronym" | "address" | "applet" | "area" | "article" | "aside" | "audio" | "b" | "base" | "basefont" | "bdo" | "big" | "blockquote" | "body" | "br" | "button" | "canvas" | "caption" | "center" | "cite" | "code" | "col" | "colgroup" | "data" | "datalist" | "dd" | "del" | "dfn" | "dir" | "div" | "dl" | "dt" | "em" | "embed" | "fieldset" | "figcaption" | "figure" | "font" | "footer" | "form" | "frame" | "frameset" | "h1" | "h2" | "h3" | "h4" | "h5" | "h6" | "head" | "header" | "hgroup" | "hr" | "html" | "i" | "iframe" | "img" | "input" | "ins" | "isindex" | "kbd" | "keygen" | "label" | "legend" | "li" | "link" | "listing" | "map" | "mark" | "marquee" | "menu" | "meta" | "meter" | "nav" | "nextid" | "nobr" | "noframes" | "noscript" | "ol" | "optgroup" | "option" | "output" | "p" | "param" | "picture" | "plaintext" | "pre" | "progress" | "q" | "rt" | "ruby" | "s" | "samp" | "script" | "section" | "select" | "slot" | "small" | "source" | "span" | "strike" | "strong" | "style" | "sub" | "sup" | "table" | "tbody" | "td" | "template" | "textarea" | "tfoot" | "th" | "thead" | "time" | "title" | "tr" | "track" | "tt" | "u" | "ul" | "var" | "video" | "wbr" | "xmp" | "circle" | "clipPath" | "defs" | "desc" | "ellipse" | "feBlend" | "feColorMatrix" | "feComponentTransfer" | "feComposite" | "feConvolveMatrix" | "feDiffuseLighting" | "feDisplacementMap" | "feDistantLight" | "feFlood" | "feFuncA" | "feFuncB" | "feFuncG" | "feFuncR" | "feGaussianBlur" | "feImage" | "feMerge" | "feMergeNode" | "feMorphology" | "feOffset" | "fePointLight" | "feSpecularLighting" | "feSpotLight" | "feTile" | "feTurbulence" | "filter" | "foreignObject" | "g" | "image" | "line" | "linearGradient" | "marker" | "mask" | "metadata" | "path" | "pattern" | "polygon" | "polyline" | "radialGradient" | "rect" | "stop" | "svg" | "switch" | "text" | "textPath" | "tspan" | "use" | "view", P extends keyof ElementTagNameMap[T], V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) => void
+
+    T extends keyof ElementTagNameMap,
+>T : T
+>ElementTagNameMap : ElementTagNameMap
+
+    P extends keyof ElementTagNameMap[T],
+>P : P
+>ElementTagNameMap : ElementTagNameMap
+>T : T
+
+    V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) {
+>V : V
+>HTMLElementTagNameMap : HTMLElementTagNameMap
+>T : T
+>P : P
+>node : Node | null
+>Node : Node
+>null : null
+>tagName : T
+>T : T
+>prop : P
+>P : P
+>value : V
+>V : V
+
+    if (assertNodeTagName(node, tagName)) {
+>assertNodeTagName(node, tagName) : boolean
+>assertNodeTagName : <T extends number | "symbol" | "object" | "a" | "abbr" | "acronym" | "address" | "applet" | "area" | "article" | "aside" | "audio" | "b" | "base" | "basefont" | "bdo" | "big" | "blockquote" | "body" | "br" | "button" | "canvas" | "caption" | "center" | "cite" | "code" | "col" | "colgroup" | "data" | "datalist" | "dd" | "del" | "dfn" | "dir" | "div" | "dl" | "dt" | "em" | "embed" | "fieldset" | "figcaption" | "figure" | "font" | "footer" | "form" | "frame" | "frameset" | "h1" | "h2" | "h3" | "h4" | "h5" | "h6" | "head" | "header" | "hgroup" | "hr" | "html" | "i" | "iframe" | "img" | "input" | "ins" | "isindex" | "kbd" | "keygen" | "label" | "legend" | "li" | "link" | "listing" | "map" | "mark" | "marquee" | "menu" | "meta" | "meter" | "nav" | "nextid" | "nobr" | "noframes" | "noscript" | "ol" | "optgroup" | "option" | "output" | "p" | "param" | "picture" | "plaintext" | "pre" | "progress" | "q" | "rt" | "ruby" | "s" | "samp" | "script" | "section" | "select" | "slot" | "small" | "source" | "span" | "strike" | "strong" | "style" | "sub" | "sup" | "table" | "tbody" | "td" | "template" | "textarea" | "tfoot" | "th" | "thead" | "time" | "title" | "tr" | "track" | "tt" | "u" | "ul" | "var" | "video" | "wbr" | "xmp" | "circle" | "clipPath" | "defs" | "desc" | "ellipse" | "feBlend" | "feColorMatrix" | "feComponentTransfer" | "feComposite" | "feConvolveMatrix" | "feDiffuseLighting" | "feDisplacementMap" | "feDistantLight" | "feFlood" | "feFuncA" | "feFuncB" | "feFuncG" | "feFuncR" | "feGaussianBlur" | "feImage" | "feMerge" | "feMergeNode" | "feMorphology" | "feOffset" | "fePointLight" | "feSpecularLighting" | "feSpotLight" | "feTile" | "feTurbulence" | "filter" | "foreignObject" | "g" | "image" | "line" | "linearGradient" | "marker" | "mask" | "metadata" | "path" | "pattern" | "polygon" | "polyline" | "radialGradient" | "rect" | "stop" | "svg" | "switch" | "text" | "textPath" | "tspan" | "use" | "view", U extends ElementTagNameMap[T]>(node: Node | null, tagName: T) => node is U
+>node : Node | null
+>tagName : T
+
+        node[prop];
+>node[prop] : ElementTagNameMap[T][P]
+>node : ElementTagNameMap[T]
+>prop : P
+    }
+}
+
diff --git a/tests/cases/compiler/intersectionsOfLargeUnions2.ts b/tests/cases/compiler/intersectionsOfLargeUnions2.ts
new file mode 100644
index 0000000000..498e238a5b
--- /dev/null
+++ b/tests/cases/compiler/intersectionsOfLargeUnions2.ts
@@ -0,0 +1,37 @@
+// @strict: true
+
+// Repro from #24233
+
+declare global {
+    interface ElementTagNameMap {
+        [index: number]: HTMLElement
+    }
+
+    interface HTMLElement {
+        [index: number]: HTMLElement;
+    }
+}
+
+export function assertIsElement(node: Node | null): node is Element {
+    let nodeType = node === null ? null : node.nodeType;
+    return nodeType === 1;
+}
+  
+export function assertNodeTagName<
+    T extends keyof ElementTagNameMap,
+    U extends ElementTagNameMap[T]>(node: Node | null, tagName: T): node is U {
+    if (assertIsElement(node)) {
+        const nodeTagName = node.tagName.toLowerCase();
+         return nodeTagName === tagName;
+    }
+    return false;
+}
+  
+export function assertNodeProperty<
+    T extends keyof ElementTagNameMap,
+    P extends keyof ElementTagNameMap[T],
+    V extends HTMLElementTagNameMap[T][P]>(node: Node | null, tagName: T, prop: P, value: V) {
+    if (assertNodeTagName(node, tagName)) {
+        node[prop];
+    }
+}