diff --git a/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache b/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
index df550e704840..109226f02b85 100644
--- a/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
@@ -296,17 +296,17 @@ export class {{classname}} {
         if ({{paramName}}) {
         {{#isCollectionFormatMulti}}
             {{paramName}}.forEach((element) => {
-                {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', <any>element){{#useHttpClient}} || formParams{{/useHttpClient}};
+                {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', <any>element){{#useHttpClient}} as any || formParams{{/useHttpClient}};
             })
         {{/isCollectionFormatMulti}}
         {{^isCollectionFormatMulti}}
-            {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', {{paramName}}.join(COLLECTION_FORMATS['{{collectionFormat}}'])){{#useHttpClient}} || formParams{{/useHttpClient}};
+            {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', {{paramName}}.join(COLLECTION_FORMATS['{{collectionFormat}}'])){{#useHttpClient}} as any || formParams{{/useHttpClient}};
         {{/isCollectionFormatMulti}}
         }
         {{/isListContainer}}
         {{^isListContainer}}
         if ({{paramName}} !== undefined) {
-            {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', <any>{{paramName}}){{#useHttpClient}} || formParams{{/useHttpClient}};
+            {{#useHttpClient}}formParams = {{/useHttpClient}}formParams.append('{{baseName}}', <any>{{paramName}}){{#useHttpClient}} as any || formParams{{/useHttpClient}};
         }
         {{/isListContainer}}
 {{/formParams}}
diff --git a/samples/client/petstore/typescript-angular-v2/npm/encoder.ts b/samples/client/petstore/typescript-angular-v2/npm/encoder.ts
index 71f99f9c7041..6fcda7b246dd 100644
--- a/samples/client/petstore/typescript-angular-v2/npm/encoder.ts
+++ b/samples/client/petstore/typescript-angular-v2/npm/encoder.ts
@@ -8,9 +8,7 @@
 export class CustomQueryEncoderHelper extends QueryEncoder {
     encodeKey(k: string): string {
         k = super.encodeKey(k);
-        return k.replace(/\+/gi, '%2B')
-            .replace(/%5B/, "[").replace(/%5D/, "]")
-            ;
+        return k.replace(/\+/gi, '%2B');
     }
     encodeValue(v: string): string {
         v = super.encodeValue(v);
diff --git a/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
index 62241086b11a..5743def7fa6b 100644
--- a/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
@@ -425,10 +425,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -498,10 +498,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
index 90b3c94edb0a..3918742abe52 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
@@ -425,10 +425,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -498,10 +498,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
index 90b3c94edb0a..3918742abe52 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -425,10 +425,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -498,10 +498,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
index 38eb9aebb525..c6c4a85ad324 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
@@ -427,10 +427,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -500,10 +500,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
index 38eb9aebb525..c6c4a85ad324 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -427,10 +427,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -500,10 +500,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
index 90b3c94edb0a..3918742abe52 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
@@ -425,10 +425,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -498,10 +498,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
index 90b3c94edb0a..3918742abe52 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -425,10 +425,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -498,10 +498,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
index 38eb9aebb525..c6c4a85ad324 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
@@ -427,10 +427,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -500,10 +500,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
index 38eb9aebb525..c6c4a85ad324 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -427,10 +427,10 @@ export class PetService {
         }
 
         if (name !== undefined) {
-            formParams = formParams.append('name', <any>name) || formParams;
+            formParams = formParams.append('name', <any>name) as any || formParams;
         }
         if (status !== undefined) {
-            formParams = formParams.append('status', <any>status) || formParams;
+            formParams = formParams.append('status', <any>status) as any || formParams;
         }
 
         return this.httpClient.post<any>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}`,
@@ -500,10 +500,10 @@ export class PetService {
         }
 
         if (additionalMetadata !== undefined) {
-            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) || formParams;
+            formParams = formParams.append('additionalMetadata', <any>additionalMetadata) as any || formParams;
         }
         if (file !== undefined) {
-            formParams = formParams.append('file', <any>file) || formParams;
+            formParams = formParams.append('file', <any>file) as any || formParams;
         }
 
         return this.httpClient.post<ApiResponse>(`${this.configuration.basePath}/pet/${encodeURIComponent(String(petId))}/uploadImage`,