Fix scope of assignments in dynamic class keys

Dynamic class keys were using the method scope for compilation,
resulting in missing declarations and runtime errors.

lib/coffee-script/nodes.js

@@ -2782,7 +2782,7 @@
       }
 
       compileNode(o) {
-        var answer, body, condition, exprs, haveSplatParam, i, ifTrue, j, k, len1, len2, m, modifiers, name, param, paramNames, params, paramsAfterSplat, ref, ref3, ref4, ref5, ref6, ref7, signature, splatParamName, thisAssignments, val, wasEmpty;
+        var answer, body, condition, exprs, haveSplatParam, i, ifTrue, j, k, len1, len2, m, methodScope, modifiers, name, param, paramNames, params, paramsAfterSplat, ref, ref3, ref4, ref5, ref6, ref7, ref8, signature, splatParamName, thisAssignments, val, wasEmpty;
         if (this.ctor) {
           if (this.isAsync) {
             this.variable.error('Class constructor may not be async');
@@ -2928,10 +2928,12 @@
           body = this.body.compileWithDeclarations(o);
         }
         if (this.isMethod) {
+          ref8 = [o.scope, o.scope.parent], methodScope = ref8[0], o.scope = ref8[1];
           name = this.name.compileToFragments(o);
           if (name[0].code === '.') {
             name.shift();
           }
+          o.scope = methodScope;
         }
         answer = this.joinFragmentArrays((function() {
           var l, len3, results;

src/nodes.coffee

@@ -2009,8 +2009,10 @@ exports.Code = class Code extends Base
 
     # We need to compile the body before method names to ensure super references are handled
     if @isMethod
+      [methodScope, o.scope] = [o.scope, o.scope.parent]
       name = @name.compileToFragments o
       name.shift() if name[0].code is '.'
+      o.scope = methodScope
 
     answer = @joinFragmentArrays (@makeCode m for m in modifiers), ' '
     answer.push @makeCode ' ' if modifiers.length and name

test/classes.coffee

@@ -845,6 +845,22 @@ test "#1392 calling `super` in methods defined on namespaced classes", ->
     @a::m = -> super
   eq 5, (new C.a).m()
 
+
+test "dynamic method names", ->
+  class A
+    "#{name = 'm'}": -> 1
+  eq 1, new A().m()
+
+  class B extends A
+    "#{name = 'm'}": -> super
+  eq 1, new B().m()
+
+  getName = -> 'm'
+  class C
+    "#{name = getName()}": -> 1
+  eq 1, new C().m()
+
+
 test "dynamic method names and super", ->
   class Base
     @m: -> 6