Better error recovery

liufengyun · liufengyun · commit 4b620c26cc86 · 2020-12-15T01:34:33.000+01:00
The test case is tests/neg/deferred-patdef.scala
diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -3225,9 +3225,13 @@ object Parsers {
             case IdPattern(id, t) => t.isEmpty
             case _ => false
           }
-          if rhs.isEmpty && !isAllIds then
-            syntaxError(ExpectedTokenButFound(EQUALS, in.token), Span(in.lastOffset))
-          PatDef(mods, lhs, tpt, rhs)
+          val rhs2 =
+            if rhs.isEmpty && !isAllIds then
+              syntaxError(ExpectedTokenButFound(EQUALS, in.token), Span(in.lastOffset))
+              errorTermTree
+            else
+              rhs
+          PatDef(mods, lhs, tpt, rhs2)
       }
     }
 
diff --git a/tests/neg-custom-args/infix.scala b/tests/neg-custom-args/infix.scala
@@ -58,7 +58,7 @@ def test() = {
   val Pair(_, _) = p
   val _ Pair _ = p   // error
   val _ `Pair` _ = p // OK
-  val (_ PP _): @unchecked = p     // OK
+  val (_ PP _) = p: @unchecked     // OK
 
   val q = Q(1, 2)
   val Q(_, _) = q

Original file line number	Diff line number	Diff line change
`@@ -3225,9 +3225,13 @@ object Parsers {`
`3225`	`3225`	`case IdPattern(id, t) => t.isEmpty`
`3226`	`3226`	`case _ => false`
`3227`	`3227`	`}`
`3228`		`- if rhs.isEmpty && !isAllIds then`
`3229`		`- syntaxError(ExpectedTokenButFound(EQUALS, in.token), Span(in.lastOffset))`
`3230`		`- PatDef(mods, lhs, tpt, rhs)`
	`3228`	`+ val rhs2 =`
	`3229`	`+ if rhs.isEmpty && !isAllIds then`
	`3230`	`+ syntaxError(ExpectedTokenButFound(EQUALS, in.token), Span(in.lastOffset))`
	`3231`	`+ errorTermTree`
	`3232`	`+ else`
	`3233`	`+ rhs`
	`3234`	`+ PatDef(mods, lhs, tpt, rhs2)`
`3231`	`3235`	`}`
`3232`	`3236`	`}`
`3233`	`3237`