syntax: handle labels for for, while and closures

[nit.git] / src / syntax / escape.nit

diff --git a/src/syntax/escape.nit b/src/syntax/escape.nit
index 8ae7c09..9cc40a7 100644 (file)
--- a/src/syntax/escape.nit
+++ b/src/syntax/escape.nit
@@ -24,10 +24,27 @@ class EscapableContext
        # Stack of blocks
        var _stack: Array[EscapableBlock] = new Array[EscapableBlock]
 
+       # Known labels
+       # (all labels, even out of scopes ones)
+       # Used to find duplicates
+       var _labels: Array[ALabel] = new Array[ALabel]
+
        # Push a new escapable block
-       fun push(block: EscapableBlock)
+       # Display error message if tere is a problem with the label
+       fun push(block: EscapableBlock, n_label: nullable ALabel)
        do
                _stack.push(block)
+               if n_label != null then
+                       var lab = n_label.n_id.to_symbol
+                       for nl in _labels do
+                               if n_label != nl and lab == nl.n_id.to_symbol then
+                                       visitor.error(n_label, "Syntax error: label {lab} already defined at {nl.location.relative_to(n_label.location)}.")
+                                       return
+                               end
+                       end
+                       _labels.add(n_label)
+                       block._lab = lab
+               end
        end
 
        # Is there no block in the stack?
@@ -39,6 +56,22 @@ class EscapableContext
                return _stack.last
        end
 
+       # Return the block associed to a label
+       # Output an error end return null if the label is not known
+       fun get_by_label(nl: ALabel): nullable EscapableBlock
+       do
+               var i = _stack.length - 1
+               var block: nullable EscapableBlock = null
+               var lab = nl.n_id.to_symbol
+               while i >= 0 do
+                       var b = _stack[i]
+                       if b.lab == lab then return b
+                       i -= 1
+               end
+               visitor.error(nl, "Syntax error: invalid label {lab}.")
+               return null
+       end
+
        # Remove the last block (the last stacked)
        fun pop
        do
@@ -60,6 +93,10 @@ class EscapableBlock
        # The syntax node of the block
        readable var _node: ANode
 
+       # The label of the block (if any)
+       # Set by the push in EscapableContext
+       readable var _lab: nullable Symbol
+
        # Is self a break closure ?
        fun is_break_block: Bool do return false
 
@@ -100,7 +137,7 @@ end
 ###############################################################################
 
 class AEscapeExpr
-special ANode
+special ALabelable
        # The associated escapable block
        readable var _escapable: nullable EscapableBlock
 
@@ -110,12 +147,16 @@ special ANode
        # Compute, set and return the associated escapable block
        fun compute_escapable_block(lctx: EscapableContext): nullable EscapableBlock
        do
-               var block: EscapableBlock
-               if lctx.is_empty then
+               var block: nullable EscapableBlock
+               var nl = n_label
+               if nl != null then
+                       block = lctx.get_by_label(nl)
+               else if lctx.is_empty then
                        lctx.visitor.error(self, "Syntax Error: '{kwname}' statment outside block.")
                        return null
+               else
+                       block = lctx.head
                end
-               block = lctx.head
                _escapable = block
                return block
        end