fix parsing '\\ to not error in the validate token step (#233)

Co-authored-by: c42f <[email protected]>

Author: Kristoffer Carlsson

src/literal_parsing.jl

@@ -243,6 +243,9 @@ function unescape_julia_string(io::IO, str::AbstractString,
         escstart = i
         i += 1
         if i >= endind
+            emit_diagnostic(diagnostics, escstart:endind-1,
+                            error="invalid escape sequence")
+            had_error = true
             break
         end
         c = str[i]

test/diagnostics.jl

@@ -75,6 +75,10 @@ end
         Diagnostic(6, 9, :error, "invalid octal escape sequence")
     @test diagnostic("x = '\\k'") ==
         Diagnostic(6, 7, :error, "invalid escape sequence")
+    @test diagnostic("'\\", allow_multiple=true) == [
+        Diagnostic(2, 2, :error, "invalid escape sequence"),
+        Diagnostic(3, 2, :error, "unterminated character literal")
+    ]
 
     # String
     @test diagnostic("x = \"abc\\xq\"") ==

test/parser_api.jl

@@ -160,4 +160,10 @@ tokensplit(str) = [kind(tok) => untokenize(tok, str) for tok in tokenize(str)]
     ]
 
     @test kind(JuliaSyntax.Token()) == K"None"
+
+    @test tokensplit("'\\") == [
+        K"'" => "'",
+        K"ErrorInvalidEscapeSequence" => "\\",
+        K"error" => ""
+    ]
 end