Parser: recover on unfinished 'as' patterns (dotnet#16404)

* Parser: recover on unfinished 'as' patterns

* Baselines

* More tests

* More recovery

* More tests

* Remove unused rule

* Baselines

* Restore the rule

* Update baseline

* Update baseline

src/Compiler/pars.fsy

@@ -3241,10 +3241,16 @@ localBinding:
 
   | opt_inline opt_mutable bindingPattern opt_topReturnTypeWithTypeConstraints recover
       { if not $5 then reportParseErrorAt (rhs parseState 5) (FSComp.SR.parsUnexpectedEndOfFileDefinition())
+        let bindingPat, mBindLhs = $3
         let optReturnType = $4
-        let mWhole = rhs2 parseState 1 (match optReturnType with None -> 3 | _ -> 4)
+        let mWhole =
+            let mStart = rhs parseState 1
+            let mEnd =
+                match optReturnType with
+                | None -> bindingPat.Range
+                | Some (_, returnInfo) -> returnInfo.Range
+            unionRanges mStart mEnd
         let mRhs = mWhole.EndRange // zero-width range at end of last good token
-        let bindingPat, mBindLhs = $3
         let localBindingBuilder =
           (fun xmlDoc attrs vis (leadingKeyword: SynLeadingKeyword) ->
             let spBind = DebugPointAtBinding.Yes(unionRanges leadingKeyword.Range mRhs)
@@ -3404,7 +3410,7 @@ constant:
 
 bindingPattern:
   | headBindingPattern
-    { $1, rhs parseState 1 }
+    { $1, $1.Range }
 
 // Subset of patterns allowed to be used in implicit ctors.
 // For a better error recovery we could replace these rules with the actual SynPat parsing
@@ -3477,6 +3483,17 @@ headBindingPattern:
   | headBindingPattern AS constrPattern
       { SynPat.As($1, $3, rhs2 parseState 1 3) }
 
+  | headBindingPattern AS recover
+      { let mAs = rhs parseState 2
+        let pat2 = SynPat.Wild(mAs.EndRange)
+        SynPat.As($1, pat2, rhs2 parseState 1 2) }
+
+  | headBindingPattern AS
+      { let mAs = rhs parseState 2
+        reportParseErrorAt mAs (FSComp.SR.parsExpectingPattern ())
+        let pat2 = SynPat.Wild(mAs.EndRange)
+        SynPat.As($1, pat2, rhs2 parseState 1 2) }
+
   | headBindingPattern BAR headBindingPattern
       { let mBar = rhs parseState 2
         SynPat.Or($1, $3, rhs2 parseState 1 3, { BarRange = mBar }) }
@@ -3751,6 +3768,11 @@ parenPattern:
   | parenPattern AS constrPattern
       { SynPat.As($1, $3, rhs2 parseState 1 3) }
 
+  | parenPattern AS recover
+      { let mAs = rhs parseState 2
+        let pat2 = SynPat.Wild(mAs.EndRange)
+        SynPat.As($1, pat2, rhs2 parseState 1 2) }
+
   | parenPattern BAR parenPattern
       { let mBar = rhs parseState 2
         SynPat.Or($1, $3, rhs2 parseState 1 3, { BarRange = mBar }) }

tests/service/PatternMatchCompilationTests.fs

@@ -611,16 +611,17 @@ let x as () = y
 let z as
 """
     dumpDiagnostics checkResults |> shouldEqual [
-        "(10,9--10,10): Unexpected symbol ',' in binding";
-        "(11,9--11,10): Unexpected symbol ':' in binding";
-        "(12,9--12,11): Unexpected symbol '::' in binding";
-        "(13,9--13,10): Unexpected symbol '&' in binding";
-        "(14,9--14,10): Unexpected symbol '|' in binding";
+        "(10,6--10,8): Expecting pattern";
+        "(11,6--11,8): Expecting pattern";
+        "(12,6--12,8): Expecting pattern";
+        "(13,6--13,8): Expecting pattern";
+        "(14,6--14,8): Expecting pattern";
         "(15,13--15,14): Unexpected symbol '=' in pattern. Expected ')' or other token.";
         "(15,9--15,10): Unmatched '('";
         "(16,0--16,3): Unexpected syntax or possible incorrect indentation: this token is offside of context started at position (15:1). Try indenting this further.\u001dTo continue using non-conforming indentation, pass the '--strict-indentation-' flag to the compiler, or set the language version to F# 7.";
         "(17,16--17,17): Unexpected identifier in pattern. Expected '(' or other token.";
-        "(20,0--20,0): Incomplete structured construct at or before this point in binding";
+        "(19,6--19,8): Expecting pattern";
+        "(20,0--20,0): Incomplete structured construct at or before this point in binding. Expected '=' or other token.";
         "(3,13--3,17): This expression was expected to have type\u001d    'int'    \u001dbut here has type\u001d    'bool'";
         "(3,4--3,10): Incomplete pattern matches on this expression. For example, the value '0' may indicate a case not covered by the pattern(s).";
         "(4,16--4,17): This expression was expected to have type\u001d    'bool'    \u001dbut here has type\u001d    'int'";
@@ -629,6 +630,11 @@ let z as
         "(6,9--6,15): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    int    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
         "(8,29--8,30): This expression was expected to have type\u001d    'unit'    \u001dbut here has type\u001d    'int'";
         "(9,26--9,27): This expression was expected to have type\u001d    'unit'    \u001dbut here has type\u001d    'int'";
+        "(10,15--10,16): This expression was expected to have type\u001d    ''a * 'b'    \u001dbut here has type\u001d    'int'";
+        "(11,11--11,12): The type 'k' is not defined.";
+        "(12,16--12,18): This expression was expected to have type\u001d    ''a list'    \u001dbut here has type\u001d    'int'";
+        "(12,4--12,13): Incomplete pattern matches on this expression. For example, the value '[]' may indicate a case not covered by the pattern(s).";
+        "(14,4--14,12): The two sides of this 'or' pattern bind different sets of variables";
         "(18,14--18,15): The value or constructor 'y' is not defined."
     ]
 
@@ -943,16 +949,17 @@ let :? x as () = y
 let :? z as
 """
     dumpDiagnostics checkResults |> shouldEqual [
-        "(10,12--10,13): Unexpected symbol ',' in binding";
-        "(11,12--11,13): Unexpected symbol ':' in binding";
-        "(12,12--12,14): Unexpected symbol '::' in binding";
-        "(13,12--13,13): Unexpected symbol '&' in binding";
-        "(14,12--14,13): Unexpected symbol '|' in binding";
+        "(10,9--10,11): Expecting pattern";
+        "(11,9--11,11): Expecting pattern";
+        "(12,9--12,11): Expecting pattern";
+        "(13,9--13,11): Expecting pattern";
+        "(14,9--14,11): Expecting pattern";
         "(15,16--15,17): Unexpected symbol '=' in pattern. Expected ')' or other token.";
         "(15,12--15,13): Unmatched '('";
         "(16,0--16,3): Unexpected syntax or possible incorrect indentation: this token is offside of context started at position (15:1). Try indenting this further.\u001dTo continue using non-conforming indentation, pass the '--strict-indentation-' flag to the compiler, or set the language version to F# 7.";
         "(17,19--17,20): Unexpected identifier in pattern. Expected '(' or other token.";
-        "(20,0--20,0): Incomplete structured construct at or before this point in binding";
+        "(19,9--19,11): Expecting pattern";
+        "(20,0--20,0): Incomplete structured construct at or before this point in binding. Expected '=' or other token.";
         "(3,7--3,8): The type 'a' is not defined.";
         "(3,4--3,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
         "(4,7--4,8): The type 'b' is not defined.";
@@ -967,10 +974,26 @@ let :? z as
         "(8,4--8,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
         "(9,7--9,8): The type 'g' is not defined.";
         "(9,4--9,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(10,7--10,8): The type 'h' is not defined.";
+        "(10,4--10,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(10,7--10,8): The type 'h' is not defined.";
+        "(10,4--10,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(11,7--11,8): The type 'j' is not defined.";
+        "(11,4--11,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(12,7--12,8): The type 'l' is not defined.";
+        "(12,4--12,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(13,7--13,8): The type 'n' is not defined.";
+        "(13,4--13,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(14,7--14,8): The type 'p' is not defined.";
+        "(14,4--14,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
         "(15,7--15,8): The type 'r' is not defined.";
         "(15,4--15,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(17,7--17,8): The type 'v' is not defined.";
+        "(17,4--17,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
         "(18,7--18,8): The type 'x' is not defined.";
-        "(18,4--18,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed."
+        "(18,4--18,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed.";
+        "(19,7--19,8): The type 'z' is not defined.";
+        "(19,4--19,8): This runtime coercion or type test from type\u001d    'a    \u001d to \u001d    'b    \u001dinvolves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed."
     ]
 
 [<Test>]
@@ -1207,7 +1230,8 @@ let y as ?z = 8
 ()
 """
     dumpDiagnostics checkResults |> shouldEqual [
-        "(7,9--7,11): Unexpected symbol '[<' in binding"
+        "(7,6--7,8): Expecting pattern";
+        "(7,9--7,11): Unexpected symbol '[<' in binding. Expected '=' or other token."
         "(8,4--8,11): This is not a valid pattern"
         "(8,4--8,16): Incomplete pattern matches on this expression."
         "(9,9--9,16): This is not a valid pattern"

tests/service/data/SyntaxTree/Expression/Object - Class 08.fs.bsl

@@ -24,7 +24,7 @@ ImplFile
                               SynArgInfo ([], false, None)), None),
                         Named (SynIdent (this, None), false, None, (4,12--4,16)),
                         None, ArbitraryAfterError ("memberCore2", (4,16--4,16)),
-                        (4,12--4,19), NoneAtInvisible,
+                        (4,12--4,16), NoneAtInvisible,
                         { LeadingKeyword = Member (4,5--4,11)
                           InlineKeyword = None
                           EqualsRange = None }), (4,5--4,16))], [], (3,2--3,9),

tests/service/data/SyntaxTree/Expression/Object - Class 13.fs.bsl

@@ -24,7 +24,7 @@ ImplFile
                               SynArgInfo ([], false, None)), None),
                         Named (SynIdent (this, None), false, None, (4,12--4,16)),
                         None, ArbitraryAfterError ("memberCore1", (4,16--4,16)),
-                        (4,12--5,5), NoneAtInvisible,
+                        (4,12--4,16), NoneAtInvisible,
                         { LeadingKeyword = Member (4,5--4,11)
                           InlineKeyword = None
                           EqualsRange = None }), (4,5--4,16));

tests/service/data/SyntaxTree/Member/Member 03.fs.bsl

@@ -66,7 +66,7 @@ ImplFile
                               (SynIdent (this, None), false, None, (5,17--5,21)),
                             None,
                             ArbitraryAfterError ("memberCore1", (5,21--5,21)),
-                            (5,4--6,4), NoneAtInvisible,
+                            (5,4--5,21), NoneAtInvisible,
                             { LeadingKeyword = Member (5,10--5,16)
                               InlineKeyword = None
                               EqualsRange = None }), (5,4--5,21));

tests/service/data/SyntaxTree/Member/Member 07.fs.bsl

@@ -64,7 +64,7 @@ ImplFile
                                   SynArgInfo ([], false, None)), None),
                             Named
                               (SynIdent (this, None), false, None, (5,17--5,21)),
-                            None, Const (Int32 2, (5,25--5,26)), (5,4--5,24),
+                            None, Const (Int32 2, (5,25--5,26)), (5,4--5,21),
                             NoneAtInvisible,
                             { LeadingKeyword = Member (5,10--5,16)
                               InlineKeyword = None

tests/service/data/SyntaxTree/Member/Member 12.fs.bsl

@@ -29,7 +29,7 @@ ImplFile
                               (SynIdent (this, None), false, None, (4,11--4,15)),
                             None,
                             ArbitraryAfterError ("memberCore2", (4,15--4,15)),
-                            (4,11--6,1), NoneAtInvisible,
+                            (4,11--4,15), NoneAtInvisible,
                             { LeadingKeyword = Member (4,4--4,10)
                               InlineKeyword = None
                               EqualsRange = None }), (4,4--4,15))], (4,4--4,15)),

tests/service/data/SyntaxTree/OperatorName/PartialActivePatternDefinitionWithoutParameters.fs.bsl

@@ -21,7 +21,7 @@ ImplFile
                     (false,
                      SynLongIdent
                        ([Boolean; parse], [(2,27--2,28)], [None; None]), None,
-                     (2,20--2,33)), (2,4--2,17), Yes (2,0--2,33),
+                     (2,20--2,33)), (2,5--2,16), Yes (2,0--2,33),
                   { LeadingKeyword = Let (2,0--2,3)
                     InlineKeyword = None
                     EqualsRange = Some (2,18--2,19) })], (2,0--2,33))],

tests/service/data/SyntaxTree/Pattern/As 01.fs

@@ -0,0 +1,4 @@
+module Module
+
+match Some 1 with
+| _ as _ -> ()

tests/service/data/SyntaxTree/Pattern/As 01.fs.bsl

@@ -0,0 +1,22 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Pattern/As 01.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Expr
+             (Match
+                (Yes (3,0--3,17),
+                 App
+                   (NonAtomic, false, Ident Some, Const (Int32 1, (3,11--3,12)),
+                    (3,6--3,12)),
+                 [SynMatchClause
+                    (As (Wild (4,2--4,3), Wild (4,7--4,8), (4,2--4,8)), None,
+                     Const (Unit, (4,12--4,14)), (4,2--4,14), Yes,
+                     { ArrowRange = Some (4,9--4,11)
+                       BarRange = Some (4,0--4,1) })], (3,0--4,14),
+                 { MatchKeyword = (3,0--3,5)
+                   WithKeyword = (3,13--3,17) }), (3,0--4,14))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--4,14), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Pattern/As 02.fs

@@ -0,0 +1,4 @@
+module Module
+
+match Some 1 with
+| _ as -> ()

tests/service/data/SyntaxTree/Pattern/As 02.fs.bsl

@@ -0,0 +1,24 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Pattern/As 02.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Expr
+             (Match
+                (Yes (3,0--3,17),
+                 App
+                   (NonAtomic, false, Ident Some, Const (Int32 1, (3,11--3,12)),
+                    (3,6--3,12)),
+                 [SynMatchClause
+                    (As (Wild (4,2--4,3), Wild (4,6--4,6), (4,2--4,6)), None,
+                     Const (Unit, (4,10--4,12)), (4,2--4,12), Yes,
+                     { ArrowRange = Some (4,7--4,9)
+                       BarRange = Some (4,0--4,1) })], (3,0--4,12),
+                 { MatchKeyword = (3,0--3,5)
+                   WithKeyword = (3,13--3,17) }), (3,0--4,12))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--4,12), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))
+
+(4,7)-(4,9) parse error Unexpected symbol '->' in pattern

tests/service/data/SyntaxTree/Pattern/As 03.fs

@@ -0,0 +1,3 @@
+module Module
+
+let _ as _ = ()

tests/service/data/SyntaxTree/Pattern/As 03.fs.bsl

@@ -0,0 +1,21 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Pattern/As 03.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  As (Wild (3,4--3,5), Wild (3,9--3,10), (3,4--3,10)), None,
+                  Const (Unit, (3,13--3,15)), (3,4--3,10), Yes (3,0--3,15),
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,11--3,12) })], (3,0--3,15))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--3,15), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Pattern/As 04.fs

@@ -0,0 +1,3 @@
+module Module
+
+let _ as = ()

tests/service/data/SyntaxTree/Pattern/As 04.fs.bsl

@@ -0,0 +1,23 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Pattern/As 04.fs", false, QualifiedNameOfFile Module, [], [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  As (Wild (3,4--3,5), Wild (3,8--3,8), (3,4--3,8)), None,
+                  Const (Unit, (3,11--3,13)), (3,4--3,8), Yes (3,0--3,13),
+                  { LeadingKeyword = Let (3,0--3,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (3,9--3,10) })], (3,0--3,13))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--3,13), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        CodeComments = [] }, set []))
+
+(3,6)-(3,8) parse error Expecting pattern

tests/service/data/SyntaxTree/Pattern/As 05.fs

@@ -0,0 +1,4 @@
+module Module
+
+match Some 1 with
+| _ as