SI-7296 Avoid crash with nested 23-param case class

The implementation restriction doesn't stop subsequent typechecking in the same compilation unit from triggering type completion which tries to synthesize the unapply method. This commit predicates generation of the unapply method on having 22 or fewer parameters.
retronym · Mar 25, 2013 · ad79d74 · ad79d74
1 parent 1187c98
commit ad79d74
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Showing 3 changed files with 13 additions and 1 deletion.
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -1373,7 +1373,9 @@ trait Namers extends MethodSynthesis {
       if (!cdef.symbol.hasAbstractFlag)
         namer.enterSyntheticSym(caseModuleApplyMeth(cdef))
 
-      namer.enterSyntheticSym(caseModuleUnapplyMeth(cdef))
+      val primaryConstructorArity = treeInfo.firstConstructorArgs(cdef.impl.body).size
+      if (primaryConstructorArity <= MaxTupleArity)
+        namer.enterSyntheticSym(caseModuleUnapplyMeth(cdef))
     }
 
     def addCopyMethod(cdef: ClassDef, namer: Namer) {

diff --git a/test/files/neg/t7296.check b/test/files/neg/t7296.check
@@ -0,0 +1,4 @@
+t7296.scala:5: error: Implementation restriction: case classes cannot have more than 22 parameters.
+  case class Foo(a: A, b: A, c: A, d: A, e: A, f: A, g: A, h: A, i: A, j: A, k: A, l: A, m: A, n: A, o: A, p: A, q: A, r: A, s: A, t: A, u: A, v: A, w: A, x: A, y: A, Z: A)
+             ^
+one error found
diff --git a/test/files/neg/t7296.scala b/test/files/neg/t7296.scala
@@ -0,0 +1,6 @@
+object Test {
+  type A = Int
+  // Emits the implementation restriction but then proceeds to crash
+  // when creating the Foo.unapply.
+  case class Foo(a: A, b: A, c: A, d: A, e: A, f: A, g: A, h: A, i: A, j: A, k: A, l: A, m: A, n: A, o: A, p: A, q: A, r: A, s: A, t: A, u: A, v: A, w: A, x: A, y: A, Z: A)
+}