Add the semantic action API 'TrapAndShiftError' instead of 'TrapError' and 'ShiftError'

3 files changed, 35 insertions, 52 deletions

diff --git a/driver/parser.go b/driver/parser.go
index af257e2..522362e 100644
--- a/driver/parser.go
+++ b/driver/parser.go
@@ -158,9 +158,6 @@ ACTION_LOOP:
 
 				return nil
 			}
-			if p.semAct != nil {
-				p.semAct.TrapError(count)
-			}
 
 			p.onError = true
 			p.shiftCount = 0
@@ -173,7 +170,7 @@ ACTION_LOOP:
 			p.shift(act * -1)
 
 			if p.semAct != nil {
-				p.semAct.ShiftError()
+				p.semAct.TrapAndShiftError(count)
 			}
 		}
 	}
diff --git a/driver/semantic_action.go b/driver/semantic_action.go
index 421a722..5bec385 100644
--- a/driver/semantic_action.go
+++ b/driver/semantic_action.go
@@ -13,11 +13,6 @@ type SemanticActionSet interface {
 	// the symbol. When the driver recovered from an error state by shifting the token, `recovered` is true.
 	Shift(tok *mldriver.Token, recovered bool)
 
-	// Shift runs when the driver shifts a symbol onto the state stack. `tok` is a token corresponding to
-	// the symbol. This function doesn't take a token as an argument because a token corresponding to
-	// the error symbol doesn't exist.
-	ShiftError()
-
 	// Reduce runs when the driver reduces an RHS of a production to its LHS. `prodNum` is a number of
 	// the production. When the driver recovered from an error state by reducing the production,
 	// `recovered` is true.
@@ -26,9 +21,11 @@ type SemanticActionSet interface {
 	// Accept runs when the driver accepts an input.
 	Accept()
 
-	// TrapError runs when the driver traps a syntax error. `n` is the number of frames that the driver discards
-	// from the state stack.
-	TrapError(n int)
+	// TrapAndShiftError runs when the driver traps a syntax error and shifts a error symbol onto the state stack.
+	// `n` is the number of frames that the driver discards from the state stack.
+	// Unlike `Shift` function, this function doesn't take a token as an argument because a token corresponding to
+	// the error symbol doesn't exist.
+	TrapAndShiftError(n int)
 
 	// MissError runs when the driver fails to trap a syntax error.
 	MissError()
@@ -125,28 +122,6 @@ func (a *SyntaxTreeActionSet) Shift(tok *mldriver.Token, recovered bool) {
 	})
 }
 
-func (a *SyntaxTreeActionSet) ShiftError() {
-	errSym := a.gram.ParsingTable.ErrorSymbol
-
-	var ast *Node
-	var cst *Node
-	if a.makeAST {
-		ast = &Node{
-			KindName: a.gram.ParsingTable.Terminals[errSym],
-		}
-	}
-	if a.makeCST {
-		cst = &Node{
-			KindName: a.gram.ParsingTable.Terminals[errSym],
-		}
-	}
-
-	a.semStack.push(&semanticFrame{
-		cst: cst,
-		ast: ast,
-	})
-}
-
 func (a *SyntaxTreeActionSet) Reduce(prodNum int, recovered bool) {
 	lhs := a.gram.ParsingTable.LHSSymbols[prodNum]
 
@@ -229,8 +204,28 @@ func (a *SyntaxTreeActionSet) Accept() {
 	a.ast = top[0].ast
 }
 
-func (a *SyntaxTreeActionSet) TrapError(n int) {
+func (a *SyntaxTreeActionSet) TrapAndShiftError(n int) {
 	a.semStack.pop(n)
+
+	errSym := a.gram.ParsingTable.ErrorSymbol
+
+	var ast *Node
+	var cst *Node
+	if a.makeAST {
+		ast = &Node{
+			KindName: a.gram.ParsingTable.Terminals[errSym],
+		}
+	}
+	if a.makeCST {
+		cst = &Node{
+			KindName: a.gram.ParsingTable.Terminals[errSym],
+		}
+	}
+
+	a.semStack.push(&semanticFrame{
+		cst: cst,
+		ast: ast,
+	})
 }
 
 func (a *SyntaxTreeActionSet) MissError() {
diff --git a/driver/semantic_action_test.go b/driver/semantic_action_test.go
index 0856b3d..ef92d92 100644
--- a/driver/semantic_action_test.go
+++ b/driver/semantic_action_test.go
@@ -23,10 +23,6 @@ func (a *testSemAct) Shift(tok *mldriver.Token, recovered bool) {
 	}
 }
 
-func (a *testSemAct) ShiftError() {
-	a.actLog = append(a.actLog, "shift/error")
-}
-
 func (a *testSemAct) Reduce(prodNum int, recovered bool) {
 	lhsSym := a.gram.ParsingTable.LHSSymbols[prodNum]
 	lhsText := a.gram.ParsingTable.NonTerminals[lhsSym]
@@ -41,8 +37,8 @@ func (a *testSemAct) Accept() {
 	a.actLog = append(a.actLog, "accept")
 }
 
-func (a *testSemAct) TrapError(n int) {
-	a.actLog = append(a.actLog, fmt.Sprintf("trap/%v", n))
+func (a *testSemAct) TrapAndShiftError(n int) {
+	a.actLog = append(a.actLog, fmt.Sprintf("trap/%v/shift/error", n))
 }
 
 func (a *testSemAct) MissError() {
@@ -110,32 +106,28 @@ char: "[a-z]";
 			},
 		},
 		{
-			caption: "when a grammar has `error` symbol, the driver calls `TrapError` and `ShiftError`.",
+			caption: "when a grammar has `error` symbol, the driver calls `TrapAndShiftError`.",
 			specSrc: specSrcWithErrorProd,
 			src:     `a; b !; c d !; e ! * *; h i j;`,
 			actLog: []string{
 				"shift/char",
-				"trap/1",
-				"shift/error",
+				"trap/1/shift/error",
 				"shift/semicolon",
 				"reduce/seq/recovered",
 
 				"shift/char",
-				"trap/2",
-				"shift/error",
+				"trap/2/shift/error",
 				"shift/semicolon",
 				"reduce/seq/recovered",
 
 				"shift/char",
 				"shift/char",
-				"trap/3",
-				"shift/error",
+				"trap/3/shift/error",
 				"shift/semicolon",
 				"reduce/seq/recovered",
 
 				"shift/char",
-				"trap/2",
-				"shift/error",
+				"trap/2/shift/error",
 				"shift/star",
 				"shift/star",
 				// When the driver shifts three times, it recovers from an error.
@@ -160,8 +152,7 @@ char: "[a-z]";
 			src:     `a !`,
 			actLog: []string{
 				"shift/char",
-				"trap/1",
-				"shift/error",
+				"trap/1/shift/error",
 			},
 		},
 		{