Add character property expression (Meet RL1.2 of UTS #18 partially)

\p{property name=property value} matches a character has the property.
When the property name is General_Category, it can be omitted.
That is, \p{Letter} equals \p{General_Category=Letter}.
Currently, only General_Category is supported.
This feature meets RL1.2 of UTS #18 partially.

RL1.2 Properties: https://unicode.org/reports/tr18/#RL1.2

1 files changed, 20 insertions, 17 deletions

diff --git a/compiler/syntax_error.go b/compiler/syntax_error.go
index df8977d..d784995 100644
--- a/compiler/syntax_error.go
+++ b/compiler/syntax_error.go
@@ -18,23 +18,26 @@ func (e *SyntaxError) Error() string {
 
 var (
 	// lexical errors
-	synErrIncompletedEscSeq = newSyntaxError("incompleted escape sequence; unexpected EOF following \\")
-	synErrInvalidEscSeq     = newSyntaxError("invalid escape sequence")
-	synErrInvalidCodePoint  = newSyntaxError("code points must consist of just 4 or 6 hex digits")
+	synErrIncompletedEscSeq     = newSyntaxError("incompleted escape sequence; unexpected EOF following \\")
+	synErrInvalidEscSeq         = newSyntaxError("invalid escape sequence")
+	synErrInvalidCodePoint      = newSyntaxError("code points must consist of just 4 or 6 hex digits")
+	synErrCharPropInvalidSymbol = newSyntaxError("invalid character property symbol")
 
 	// syntax errors
-	synErrUnexpectedToken   = newSyntaxError("unexpected token")
-	synErrNullPattern       = newSyntaxError("a pattern must be a non-empty byte sequence")
-	synErrAltLackOfOperand  = newSyntaxError("an alternation expression must have operands")
-	synErrRepNoTarget       = newSyntaxError("a repeat expression must have an operand")
-	synErrGroupNoElem       = newSyntaxError("a grouping expression must include at least one character")
-	synErrGroupUnclosed     = newSyntaxError("unclosed grouping expression")
-	synErrGroupNoInitiator  = newSyntaxError(") needs preceding (")
-	synErrGroupInvalidForm  = newSyntaxError("invalid grouping expression")
-	synErrBExpNoElem        = newSyntaxError("a bracket expression must include at least one character")
-	synErrBExpUnclosed      = newSyntaxError("unclosed bracket expression")
-	synErrBExpInvalidForm   = newSyntaxError("invalid bracket expression")
-	synErrRangeInvalidOrder = newSyntaxError("a range expression with invalid order")
-	synErrCPExpInvalidForm  = newSyntaxError("invalid code point expression")
-	synErrCPExpOutOfRange   = newSyntaxError("a code point must be between U+0000 to U+10FFFF")
+	synErrUnexpectedToken        = newSyntaxError("unexpected token")
+	synErrNullPattern            = newSyntaxError("a pattern must be a non-empty byte sequence")
+	synErrAltLackOfOperand       = newSyntaxError("an alternation expression must have operands")
+	synErrRepNoTarget            = newSyntaxError("a repeat expression must have an operand")
+	synErrGroupNoElem            = newSyntaxError("a grouping expression must include at least one character")
+	synErrGroupUnclosed          = newSyntaxError("unclosed grouping expression")
+	synErrGroupNoInitiator       = newSyntaxError(") needs preceding (")
+	synErrGroupInvalidForm       = newSyntaxError("invalid grouping expression")
+	synErrBExpNoElem             = newSyntaxError("a bracket expression must include at least one character")
+	synErrBExpUnclosed           = newSyntaxError("unclosed bracket expression")
+	synErrBExpInvalidForm        = newSyntaxError("invalid bracket expression")
+	synErrRangeInvalidOrder      = newSyntaxError("a range expression with invalid order")
+	synErrCPExpInvalidForm       = newSyntaxError("invalid code point expression")
+	synErrCPExpOutOfRange        = newSyntaxError("a code point must be between U+0000 to U+10FFFF")
+	synErrCharPropExpInvalidForm = newSyntaxError("invalid character property expression")
+	synErrCharPropUnsupported    = newSyntaxError("unsupported character property")
 )