diff --git a/.eslintrc b/.eslintrc
index 22749b4b7c..6acf2455fa 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -5,7 +5,8 @@
     "prettier"
   ],
   "rules": {
-    "prettier/prettier": ["error", { "trailingComma": "all" }]
+    "prettier/prettier": ["error", { "trailingComma": "all" }],
+    "no-case-declarations": "error"
   },
   "env": {
     "node": true
diff --git a/src/parser/expression.js b/src/parser/expression.js
index 9a3ea211cc..642bffa83c 100644
--- a/src/parser/expression.js
+++ b/src/parser/expression.js
@@ -676,7 +676,7 @@ export default class ExpressionParser extends LValParser {
       case tt._yield:
         if (this.state.inGenerator) this.unexpected();
 
-      case tt.name:
+      case tt.name: {
         node = this.startNode();
         const allowAwait = this.state.value === "await" && this.state.inAsync;
         const allowYield = this.shouldAllowYieldIdentifier();
@@ -705,29 +705,29 @@ export default class ExpressionParser extends LValParser {
         }
 
         return id;
+      }
 
-      case tt._do:
-        // TODO
-        if (true) {
-          this.expectPlugin("doExpressions");
-          const node = this.startNode();
-          this.next();
-          const oldInFunction = this.state.inFunction;
-          const oldLabels = this.state.labels;
-          this.state.labels = [];
-          this.state.inFunction = false;
-          node.body = this.parseBlock(false);
-          this.state.inFunction = oldInFunction;
-          this.state.labels = oldLabels;
-          return this.finishNode(node, "DoExpression");
-        }
+      case tt._do: {
+        this.expectPlugin("doExpressions");
+        const node = this.startNode();
+        this.next();
+        const oldInFunction = this.state.inFunction;
+        const oldLabels = this.state.labels;
+        this.state.labels = [];
+        this.state.inFunction = false;
+        node.body = this.parseBlock(false);
+        this.state.inFunction = oldInFunction;
+        this.state.labels = oldLabels;
+        return this.finishNode(node, "DoExpression");
+      }
 
-      case tt.regexp:
+      case tt.regexp: {
         const value = this.state.value;
         node = this.parseLiteral(value.value, "RegExpLiteral");
         node.pattern = value.pattern;
         node.flags = value.flags;
         return node;
+      }
 
       case tt.num:
         return this.parseLiteral(this.state.value, "NumericLiteral");
@@ -781,7 +781,7 @@ export default class ExpressionParser extends LValParser {
       case tt.backQuote:
         return this.parseTemplate(false);
 
-      case tt.doubleColon:
+      case tt.doubleColon: {
         node = this.startNode();
         this.next();
         node.object = null;
@@ -794,6 +794,7 @@ export default class ExpressionParser extends LValParser {
             "Binding should be performed on object property.",
           );
         }
+      }
 
       default:
         throw this.unexpected();
diff --git a/src/parser/lval.js b/src/parser/lval.js
index d5156a634c..01ab50f485 100644
--- a/src/parser/lval.js
+++ b/src/parser/lval.js
@@ -69,13 +69,14 @@ export default class LValParser extends NodeUtils {
           this.toAssignable(node.value, isBinding, contextDescription);
           break;
 
-        case "SpreadElement":
+        case "SpreadElement": {
           this.checkToRestConversion(node);
 
           node.type = "RestElement";
           const arg = node.argument;
           this.toAssignable(arg, isBinding, contextDescription);
           break;
+        }
 
         case "ArrayExpression":
           node.type = "ArrayPattern";
@@ -211,11 +212,12 @@ export default class LValParser extends NodeUtils {
       case tt.name:
         return this.parseBindingIdentifier();
 
-      case tt.bracketL:
+      case tt.bracketL: {
         const node = this.startNode();
         this.next();
         node.elements = this.parseBindingList(tt.bracketR, true);
         return this.finishNode(node, "ArrayPattern");
+      }
 
       case tt.braceL:
         return this.parseObj(true);
diff --git a/src/plugins/typescript.js b/src/plugins/typescript.js
index d99aeaf6cd..7d6971fa73 100644
--- a/src/plugins/typescript.js
+++ b/src/plugins/typescript.js
@@ -540,7 +540,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       switch (this.state.type) {
         case tt.name:
         case tt._void:
-        case tt._null:
+        case tt._null: {
           const type = this.match(tt._void)
             ? "TSVoidKeyword"
             : this.match(tt._null)
@@ -552,6 +552,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             return this.finishNode(node, type);
           }
           return this.tsParseTypeReference();
+        }
         case tt.string:
         case tt.num:
         case tt._true:
@@ -573,13 +574,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             return this.finishNode(node, "TSLiteralType");
           }
           break;
-        case tt._this:
+        case tt._this: {
           const thisKeyword = this.tsParseThisTypeNode();
           if (this.isContextual("is") && !this.hasPrecedingLineBreak()) {
             return this.tsParseThisTypePredicate(thisKeyword);
           } else {
             return thisKeyword;
           }
+        }
         case tt._typeof:
           return this.tsParseTypeQuery();
         case tt.braceL:
@@ -1038,13 +1040,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         case tt._var:
         case tt._let:
           return this.parseVarStatement(nany, this.state.type);
-        case tt.name:
+        case tt.name: {
           const value = this.state.value;
           if (value === "global") {
             return this.tsParseAmbientExternalModuleDeclaration(nany);
           } else {
             return this.tsParseDeclaration(nany, value, /* next */ true);
           }
+        }
       }
     }
 
@@ -1064,14 +1067,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
     tsParseExpressionStatement(node: any, expr: N.Identifier): ?N.Declaration {
       switch (expr.name) {
-        case "declare":
+        case "declare": {
           const declaration = this.tsTryParseDeclare(node);
           if (declaration) {
             declaration.declare = true;
             return declaration;
           }
           break;
-
+        }
         case "global":
           // `global { }` (with no `declare`) may appear inside an ambient module declaration.
           // Would like to use tsParseAmbientExternalModuleDeclaration here, but already ran past "global".
diff --git a/src/tokenizer/index.js b/src/tokenizer/index.js
index cb3fd8b57d..f9ece03f80 100644
--- a/src/tokenizer/index.js
+++ b/src/tokenizer/index.js
@@ -595,11 +595,13 @@ export default class Tokenizer extends LocationParser {
         ++this.state.pos;
         return this.finishToken(tt.backQuote);
 
-      case 48: // '0'
+      case 48: {
+        // '0'
         const next = this.input.charCodeAt(this.state.pos + 1);
         if (next === 120 || next === 88) return this.readRadixNumber(16); // '0x', '0X' - hex number
         if (next === 111 || next === 79) return this.readRadixNumber(8); // '0o', '0O' - octal number
         if (next === 98 || next === 66) return this.readRadixNumber(2); // '0b', '0B' - binary number
+      }
       // Anything else beginning with a digit is an integer, octal
       // number, or float.
       case 49: