Checker/patterns: recover on unresolved long identifiers

docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

@@ -40,6 +40,7 @@
 * Symbols: Add GenericArguments to FSharpEntity ([PR #16470](https://github.com/dotnet/fsharp/pull/16470))
 * Parser: more 'as' pattern recovery ([PR #16837](https://github.com/dotnet/fsharp/pull/16837))
 * Add extended data for `DefinitionsInSigAndImplNotCompatibleAbbreviationsDiffer` (FS0318). ([PR #16811](https://github.com/dotnet/fsharp/pull/16811)))
+* Checker/patterns: recover on unresolved long identifiers ([PR #16842](https://github.com/dotnet/fsharp/pull/16842))
 
 ### Changed
 

src/Compiler/Checking/CheckPatterns.fs

@@ -293,7 +293,11 @@ and TcPat warnOnUpper (cenv: cenv) env valReprInfo vFlags (patEnv: TcPatLinearEn
         TcPatAnds warnOnUpper cenv env vFlags patEnv ty pats m
 
     | SynPat.LongIdent (longDotId=longDotId; typarDecls=tyargs; argPats=args; accessibility=vis; range=m) ->
-        TcPatLongIdent warnOnUpper cenv env ad valReprInfo vFlags patEnv ty (longDotId, tyargs, args, vis, m)
+        try
+            TcPatLongIdent warnOnUpper cenv env ad valReprInfo vFlags patEnv ty (longDotId, tyargs, args, vis, m)
+        with RecoverableException e ->
+            errorRecovery e m
+            (fun _ -> TPat_error m), patEnv
 
     | SynPat.QuoteExpr(_, m) ->
         errorR (Error(FSComp.SR.tcInvalidPattern(), m))

tests/FSharp.Compiler.ComponentTests/Language/BooleanReturningAndReturnTypeDirectedPartialActivePatternTests.fs

@@ -101,17 +101,26 @@ but here has type
         (Error 39, Line 4, Col 7, Line 4, Col 13,
          "The value or constructor 'result' is not defined. Maybe you want one of the following:
    Result")
+        (Warning 20, Line 3, Col 1, Line 5, Col 15,
+         "The result of this expression has type 'string' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.");
         (Error 1, Line 8, Col 3, Line 8, Col 13,
          "This expression was expected to have type
     'string -> bool'    
 but here has type
     'bool'    ")
         (Error 39, Line 8, Col 7, Line 8, Col 13,
          "The value or constructor 'result' is not defined. Maybe you want one of the following:
+   Result");
+        (Error 39, Line 8, Col 17, Line 8, Col 23,
+         "The value or constructor 'result' is not defined. Maybe you want one of the following:
    Result")
+        (Warning 20, Line 7, Col 1, Line 9, Col 15,
+         "The result of this expression has type 'string' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.");
         (Error 1, Line 12, Col 3, Line 12, Col 30,
          "This expression was expected to have type
     'string -> bool'    
 but here has type
     'bool'    ")
+        (Warning 20, Line 11, Col 1, Line 13, Col 21,
+         "The result of this expression has type 'string' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
     ]

tests/service/PatternMatchCompilationTests.fs

@@ -1260,4 +1260,17 @@ let f : obj -> _ =
     assertHasSymbolUsages ["i"] checkResults
     dumpDiagnostics checkResults |> shouldEqual [
         "(5,6--5,18): Feature 'non-variable patterns to the right of 'as' patterns' is not available in F# 5.0. Please use language version 6.0 or greater."
-    ]
+    ]
+
+[<Test>]
+let ``Unresolved name - Qualifier 01`` () =
+    let _, checkResults = getParseAndCheckResults """
+match None with
+| Foo.Bar -> let a = 1 in ignore a
+| Some b -> ignore b
+"""
+    assertHasSymbolUsages ["a"; "b"] checkResults
+    dumpDiagnostics checkResults |> shouldEqual [
+        "(3,2--3,5): The namespace or module 'Foo' is not defined."
+        "(2,6--2,10): Incomplete pattern matches on this expression."
+    ]