Report an error for class declarations in statement position

tsc/internal/checker/checker.go

@@ -4343,6 +4343,9 @@ func (c *Checker) checkClassDeclaration(node *ast.Node) {
 	if node.Name() == nil && !ast.HasSyntacticModifier(node, ast.ModifierFlagsDefault) {
 		c.grammarErrorOnFirstToken(node, diagnostics.A_class_declaration_without_the_default_modifier_must_have_a_name)
 	}
+	if !c.containerAllowsBlockScopedVariable(node.Parent) {
+		c.grammarErrorOnNode(node, diagnostics.X_0_declarations_can_only_be_declared_inside_a_block, "class")
+	}
 	c.checkClassLikeDeclaration(node)
 	c.checkSourceElements(node.Members())
 	c.checkConstructorDeclaredProperties(node)

tsc/testdata/baselines/reference/compiler/classDeclarationInStatementPosition.errors.txt

@@ -0,0 +1,66 @@
+a.ts(3,17): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(4,25): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(5,20): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(6,10): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(7,16): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(8,27): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(9,27): error TS1156: 'class' declarations can only be declared inside a block.
+a.ts(10,11): error TS1344: A label is not allowed here.
+a.ts(10,24): error TS1156: 'class' declarations can only be declared inside a block.
+b.js(1,26): error TS1156: 'class' declarations can only be declared inside a block.
+
+
+==== a.ts (9 errors) ====
+    declare const cond: boolean;
+
+    if (cond) class C1 {}
+                    ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    if (cond) {} else class C2 {}
+                            ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    while (cond) class C3 {}
+                       ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    do class C4 {} while (cond);
+             ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    for (;;) class C5 {}
+                   ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    for (const k in {}) class C6 {}
+                              ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    for (const v of []) class C7 {}
+                              ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+    if (cond) label: class C8 {}
+              ~~~~~
+!!! error TS1344: A label is not allowed here.
+                           ~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+
+    // OK
+    if (cond) {
+        class C10 {}
+    }
+    class C11 {}
+    switch (0) {
+        case 0:
+            class C12 {}
+    }
+    namespace N {
+        class C13 {}
+    }
+    function f() {
+        class C14 {}
+        return class C15 {};
+    }
+    let x;
+    if (cond) x = class C16 {};
+
+==== b.js (1 errors) ====
+    if (Math.random()) class C17 {}
+                             ~~~
+!!! error TS1156: 'class' declarations can only be declared inside a block.
+

tsc/testdata/baselines/reference/compiler/classDeclarationInStatementPosition.js

@@ -0,0 +1,97 @@
+//// [tests/cases/compiler/classDeclarationInStatementPosition.ts] ////
+
+//// [a.ts]
+declare const cond: boolean;
+
+if (cond) class C1 {}
+if (cond) {} else class C2 {}
+while (cond) class C3 {}
+do class C4 {} while (cond);
+for (;;) class C5 {}
+for (const k in {}) class C6 {}
+for (const v of []) class C7 {}
+if (cond) label: class C8 {}
+
+// OK
+if (cond) {
+    class C10 {}
+}
+class C11 {}
+switch (0) {
+    case 0:
+        class C12 {}
+}
+namespace N {
+    class C13 {}
+}
+function f() {
+    class C14 {}
+    return class C15 {};
+}
+let x;
+if (cond) x = class C16 {};
+
+//// [b.js]
+if (Math.random()) class C17 {}
+
+
+//// [a.js]
+"use strict";
+if (cond)
+    class C1 {
+    }
+if (cond) { }
+else
+    class C2 {
+    }
+while (cond)
+    class C3 {
+    }
+do
+    class C4 {
+    }
+while (cond);
+for (;;)
+    class C5 {
+    }
+for (const k in {})
+    class C6 {
+    }
+for (const v of [])
+    class C7 {
+    }
+if (cond)
+    label: class C8 {
+    }
+// OK
+if (cond) {
+    class C10 {
+    }
+}
+class C11 {
+}
+switch (0) {
+    case 0:
+        class C12 {
+        }
+}
+var N;
+(function (N) {
+    class C13 {
+    }
+})(N || (N = {}));
+function f() {
+    class C14 {
+    }
+    return class C15 {
+    };
+}
+let x;
+if (cond)
+    x = class C16 {
+    };
+//// [b.js]
+"use strict";
+if (Math.random())
+    class C17 {
+    }

tsc/testdata/baselines/reference/compiler/classDeclarationInStatementPosition.symbols

@@ -0,0 +1,82 @@
+//// [tests/cases/compiler/classDeclarationInStatementPosition.ts] ////
+
+=== a.ts ===
+declare const cond: boolean;
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+
+if (cond) class C1 {}
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+>C1 : Symbol(C1, Decl(a.ts, 2, 9))
+
+if (cond) {} else class C2 {}
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+>C2 : Symbol(C2, Decl(a.ts, 3, 17))
+
+while (cond) class C3 {}
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+>C3 : Symbol(C3, Decl(a.ts, 4, 12))
+
+do class C4 {} while (cond);
+>C4 : Symbol(C4, Decl(a.ts, 5, 2))
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+
+for (;;) class C5 {}
+>C5 : Symbol(C5, Decl(a.ts, 6, 8))
+
+for (const k in {}) class C6 {}
+>k : Symbol(k, Decl(a.ts, 7, 10))
+>C6 : Symbol(C6, Decl(a.ts, 7, 19))
+
+for (const v of []) class C7 {}
+>v : Symbol(v, Decl(a.ts, 8, 10))
+>C7 : Symbol(C7, Decl(a.ts, 8, 19))
+
+if (cond) label: class C8 {}
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+>C8 : Symbol(C8, Decl(a.ts, 9, 16))
+
+// OK
+if (cond) {
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+
+    class C10 {}
+>C10 : Symbol(C10, Decl(a.ts, 12, 11))
+}
+class C11 {}
+>C11 : Symbol(C11, Decl(a.ts, 14, 1))
+
+switch (0) {
+    case 0:
+        class C12 {}
+>C12 : Symbol(C12, Decl(a.ts, 17, 11))
+}
+namespace N {
+>N : Symbol(N, Decl(a.ts, 19, 1))
+
+    class C13 {}
+>C13 : Symbol(C13, Decl(a.ts, 20, 13))
+}
+function f() {
+>f : Symbol(f, Decl(a.ts, 22, 1))
+
+    class C14 {}
+>C14 : Symbol(C14, Decl(a.ts, 23, 14))
+
+    return class C15 {};
+>C15 : Symbol(C15, Decl(a.ts, 25, 10))
+}
+let x;
+>x : Symbol(x, Decl(a.ts, 27, 3))
+
+if (cond) x = class C16 {};
+>cond : Symbol(cond, Decl(a.ts, 0, 13))
+>x : Symbol(x, Decl(a.ts, 27, 3))
+>C16 : Symbol(C16, Decl(a.ts, 28, 13))
+
+=== b.js ===
+if (Math.random()) class C17 {}
+>Math.random : Symbol(Math.random, Decl(lib.es5.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>random : Symbol(Math.random, Decl(lib.es5.d.ts, --, --))
+>C17 : Symbol(C17, Decl(b.js, 0, 18))
+

tsc/testdata/baselines/reference/compiler/classDeclarationInStatementPosition.types

@@ -0,0 +1,93 @@
+//// [tests/cases/compiler/classDeclarationInStatementPosition.ts] ////
+
+=== a.ts ===
+declare const cond: boolean;
+>cond : boolean
+
+if (cond) class C1 {}
+>cond : boolean
+>C1 : C1
+
+if (cond) {} else class C2 {}
+>cond : boolean
+>C2 : C2
+
+while (cond) class C3 {}
+>cond : boolean
+>C3 : C3
+
+do class C4 {} while (cond);
+>C4 : C4
+>cond : false
+
+for (;;) class C5 {}
+>C5 : C5
+
+for (const k in {}) class C6 {}
+>k : string
+>{} : {}
+>C6 : C6
+
+for (const v of []) class C7 {}
+>v : never
+>[] : never[]
+>C7 : C7
+
+if (cond) label: class C8 {}
+>cond : boolean
+>label : any
+>C8 : C8
+
+// OK
+if (cond) {
+>cond : boolean
+
+    class C10 {}
+>C10 : C10
+}
+class C11 {}
+>C11 : C11
+
+switch (0) {
+>0 : 0
+
+    case 0:
+>0 : 0
+
+        class C12 {}
+>C12 : C12
+}
+namespace N {
+>N : typeof N
+
+    class C13 {}
+>C13 : C13
+}
+function f() {
+>f : () => typeof C15
+
+    class C14 {}
+>C14 : C14
+
+    return class C15 {};
+>class C15 {} : typeof C15
+>C15 : typeof C15
+}
+let x;
+>x : any
+
+if (cond) x = class C16 {};
+>cond : boolean
+>x = class C16 {} : typeof C16
+>x : any
+>class C16 {} : typeof C16
+>C16 : typeof C16
+
+=== b.js ===
+if (Math.random()) class C17 {}
+>Math.random() : number
+>Math.random : () => number
+>Math : Math
+>random : () => number
+>C17 : C17
+

tsc/testdata/tests/cases/compiler/classDeclarationInStatementPosition.ts

@@ -0,0 +1,39 @@
+// @target: es2015
+// @allowJs: true
+// @outDir: out
+
+// https://github.com/microsoft/TypeScript/issues/22682
+
+// @filename: a.ts
+declare const cond: boolean;
+
+if (cond) class C1 {}
+if (cond) {} else class C2 {}
+while (cond) class C3 {}
+do class C4 {} while (cond);
+for (;;) class C5 {}
+for (const k in {}) class C6 {}
+for (const v of []) class C7 {}
+if (cond) label: class C8 {}
+
+// OK
+if (cond) {
+    class C10 {}
+}
+class C11 {}
+switch (0) {
+    case 0:
+        class C12 {}
+}
+namespace N {
+    class C13 {}
+}
+function f() {
+    class C14 {}
+    return class C15 {};
+}
+let x;
+if (cond) x = class C16 {};
+
+// @filename: b.js
+if (Math.random()) class C17 {}