Syntax: allow multiple expressions in a case condition

spec/compiler/formatter/formatter_spec.cr

@@ -419,6 +419,7 @@ describe Crystal::Formatter do
   assert_format "case  1 \n when  .foo? \n 3 \n end", "case 1\nwhen .foo?\n  3\nend"
   assert_format "case 1\nwhen 1 then\n2\nwhen 3\n4\nend", "case 1\nwhen 1\n  2\nwhen 3\n  4\nend"
   assert_format "case  1 \n when 2 \n 3 \n else 4 \n end", "case 1\nwhen 2\n  3\nelse 4\nend"
+  assert_format "case  1 , 2 \n when 3 , 4 \n 5 \n end", "case 1, 2\nwhen 3, 4\n  5\nend"
 
   assert_format "foo.@bar"
 

spec/compiler/macro/macro_methods_spec.cr

@@ -741,10 +741,10 @@ describe "macro methods" do
   end
 
   describe "case methods" do
-    case_node = Case.new(NumberLiteral.new(1), [When.new([NumberLiteral.new(2), NumberLiteral.new(3)] of ASTNode, NumberLiteral.new(4))], NumberLiteral.new(5))
+    case_node = Case.new([NumberLiteral.new(1)] of ASTNode, [When.new([NumberLiteral.new(2), NumberLiteral.new(3)] of ASTNode, NumberLiteral.new(4))], NumberLiteral.new(5))
 
     it "executes cond" do
-      assert_macro "x", %({{x.cond}}), [case_node] of ASTNode, "1"
+      assert_macro "x", %({{x.conds}}), [case_node] of ASTNode, "[1]"
     end
 
     it "executes whens" do

spec/compiler/normalize/case_spec.cr

@@ -48,4 +48,20 @@ describe "Normalize: case" do
   it "normalizes case with nil to is_a?" do
     assert_expand_second "x = 1; case x; when nil; 'b'; end", "if x.is_a?(::Nil)\n  'b'\nend"
   end
+
+  it "normalizes case with multiple expressions" do
+    assert_expand_second "x, y = 1, 2; case x, y; when 2, 3; 4; end", "if 2 === x && 3 === y\n  4\nend"
+  end
+
+  it "normalizes case with multiple expressions with underscore" do
+    assert_expand_second "x, y = 1, 2; case x, y; when 2, _; 4; end", "if 2 === x\n  4\nend"
+  end
+
+  it "normalizes case with multiple expressions with all underscores" do
+    assert_expand_second "x, y = 1, 2; case x, y; when _, _; 4; end", "if true\n  4\nend"
+  end
+
+  it "normalizes case with single expressions with underscore" do
+    assert_expand_second "x = 1; case x; when _; 2; end", "if true\n  2\nend"
+  end
 end

spec/compiler/parser/parser_spec.cr

@@ -844,21 +844,25 @@ describe "Parser" do
   it_parses "require \"foo\"", Require.new("foo")
   it_parses "require \"foo\"; [1]", [Require.new("foo"), ([1.int32] of ASTNode).array]
 
-  it_parses "case 1; when 1; 2; else; 3; end", Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
-  it_parses "case 1; when 0, 1; 2; else; 3; end", Case.new(1.int32, [When.new([0.int32, 1.int32] of ASTNode, 2.int32)], 3.int32)
-  it_parses "case 1\nwhen 1\n2\nelse\n3\nend", Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
-  it_parses "case 1\nwhen 1\n2\nend", Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)])
-  it_parses "case / /; when / /; / /; else; / /; end", Case.new(regex(" "), [When.new([regex(" ")] of ASTNode, regex(" "))], regex(" "))
-  it_parses "case / /\nwhen / /\n/ /\nelse\n/ /\nend", Case.new(regex(" "), [When.new([regex(" ")] of ASTNode, regex(" "))], regex(" "))
-
-  it_parses "case 1; when 1 then 2; else; 3; end", Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
-  it_parses "case 1\nwhen 1\n2\nend\nif a\nend", [Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)]), If.new("a".call)]
-  it_parses "case\n1\nwhen 1\n2\nend\nif a\nend", [Case.new(1.int32, [When.new([1.int32] of ASTNode, 2.int32)]), If.new("a".call)]
-
-  it_parses "case 1\nwhen .foo\n2\nend", Case.new(1.int32, [When.new([Call.new(ImplicitObj.new, "foo")] of ASTNode, 2.int32)])
+  it_parses "case 1; when 1; 2; else; 3; end", Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
+  it_parses "case 1; when 0, 1; 2; else; 3; end", Case.new([1.int32] of ASTNode, [When.new([0.int32, 1.int32] of ASTNode, 2.int32)], 3.int32)
+  it_parses "case 1\nwhen 1\n2\nelse\n3\nend", Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
+  it_parses "case 1\nwhen 1\n2\nend", Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)])
+  it_parses "case / /; when / /; / /; else; / /; end", Case.new([regex(" ")] of ASTNode, [When.new([regex(" ")] of ASTNode, regex(" "))], regex(" "))
+  it_parses "case / /\nwhen / /\n/ /\nelse\n/ /\nend", Case.new([regex(" ")] of ASTNode, [When.new([regex(" ")] of ASTNode, regex(" "))], regex(" "))
+
+  it_parses "case 1; when 1 then 2; else; 3; end", Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)], 3.int32)
+  it_parses "case 1\nwhen 1\n2\nend\nif a\nend", [Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)]), If.new("a".call)]
+  it_parses "case\n1\nwhen 1\n2\nend\nif a\nend", [Case.new([1.int32] of ASTNode, [When.new([1.int32] of ASTNode, 2.int32)]), If.new("a".call)]
+
+  it_parses "case 1\nwhen .foo\n2\nend", Case.new([1.int32] of ASTNode, [When.new([Call.new(ImplicitObj.new, "foo")] of ASTNode, 2.int32)])
   it_parses "case when 1\n2\nend", Case.new(nil, [When.new([1.int32] of ASTNode, 2.int32)])
   it_parses "case \nwhen 1\n2\nend", Case.new(nil, [When.new([1.int32] of ASTNode, 2.int32)])
 
+  it_parses "case 1, 2, 3; when 4, 5, 6; 7; else; 8; end", Case.new([1.int32, 2.int32, 3.int32] of ASTNode, [When.new([4.int32, 5.int32, 6.int32] of ASTNode, 7.int32)], 8.int32)
+  it_parses "case 1; when _; 2; end", Case.new([1.int32] of ASTNode, [When.new([Underscore.new] of ASTNode, 2.int32)])
+  assert_syntax_error "case 1, 2; when 3; 4; end", "wrong number of when expressions (given 1, expected 2)", 1, 12
+
   it_parses "def foo(x); end; x", [Def.new("foo", ["x".arg]), "x".call]
   it_parses "def foo; / /; end", Def.new("foo", body: regex(" "))
 

src/compiler/crystal/macros/methods.cr

@@ -969,8 +969,14 @@ module Crystal
   class Case
     def interpret(method, args, block, interpreter)
       case method
-      when "cond"
-        interpret_argless_method(method, args) { cond || Nop.new }
+      when "conds"
+        interpret_argless_method(method, args) do
+          if conds = self.conds
+            ArrayLiteral.new(conds)
+          else
+            Nop.new
+          end
+        end
       when "whens"
         interpret_argless_method(method, args) { ArrayLiteral.map whens, &.itself }
       when "else"

src/compiler/crystal/semantic/literal_expander.cr

@@ -345,36 +345,67 @@ module Crystal
     #     if temp.is_a?(Bar)
     #       1
     #     end
+    #
+    # We also take care to expand multiple conds
+    #
+    # From:
+    #
+    #     case x, y
+    #     when 1, 2
+    #       3
+    #     end
+    #
+    # To:
+    #
+    #     if 1 === x && y === 2
+    #       3
+    #     end
     def expand(node : Case)
-      node_cond = node.cond
-      if node_cond
-        case node_cond
-        when Var, InstanceVar
-          temp_var = node.cond
-        when Assign
-          temp_var = node_cond.target
-          assign = node_cond
-        else
-          temp_var = new_temp_var
-          assign = Assign.new(temp_var.clone, node_cond)
+      conds = node.conds
+      multi = false
+
+      if conds
+        multi = conds.size > 1
+        assigns = [] of ASTNode
+        temp_vars = conds.map do |node_cond|
+          case node_cond
+          when Var, InstanceVar
+            temp_var = node_cond
+          when Assign
+            temp_var = node_cond.target
+            assigns << node_cond
+          else
+            temp_var = new_temp_var
+            assigns << Assign.new(temp_var.clone, node_cond)
+          end
+          temp_var
         end
       end
 
       a_if = nil
       final_if = nil
       node.whens.each do |wh|
         final_comp = nil
-        wh.conds.each do |cond|
+        wh.conds.each_with_index do |cond, i|
+          next if cond.is_a?(Underscore)
+
+          temp_var = temp_vars.try &.[multi ? i : 0]
           comp = case_when_comparison(temp_var, cond).at(cond)
 
           if final_comp
-            final_comp = Or.new(final_comp, comp)
+            final_comp = if multi
+                           And.new(final_comp, comp)
+                         else
+                           Or.new(final_comp, comp)
+                         end
           else
             final_comp = comp
           end
         end
 
-        wh_if = If.new(final_comp.not_nil!, wh.body)
+        final_comp ||= BoolLiteral.new(true)
+
+        wh_if = If.new(final_comp, wh.body)
         if a_if
           a_if.else = wh_if
         else
@@ -388,8 +419,9 @@ module Crystal
       end
 
       final_if = final_if.not_nil!
-      final_exp = if assign
-                    Expressions.new([assign, final_if] of ASTNode)
+      final_exp = if assigns && !assigns.empty?
+                    assigns << final_if
+                    Expressions.new(assigns)
                   else
                     final_if
                   end

src/compiler/crystal/syntax/ast.cr

@@ -1131,23 +1131,24 @@ module Crystal
   end
 
   class Case < ASTNode
-    property :cond
+    property conds : Array(ASTNode)?
     property :whens
     property :else
 
-    def initialize(@cond, @whens, @else = nil)
+    def initialize(@conds : Array(ASTNode)?, @whens, @else = nil)
     end
 
     def accept_children(visitor)
+      @conds.try &.each &.accept visitor
       @whens.each &.accept visitor
       @else.try &.accept visitor
     end
 
     def clone_without_location
-      Case.new(@cond.clone, @whens.clone, @else.clone)
+      Case.new(@conds.clone, @whens.clone, @else.clone)
     end
 
-    def_equals_and_hash @cond, @whens, @else
+    def_equals_and_hash @conds, @whens, @else
   end
 
   # Node that represents an implicit obj in:

src/compiler/crystal/syntax/parser.cr

@@ -2097,8 +2097,22 @@ module Crystal
     def parse_case
       slash_is_regex!
       next_token_skip_space_or_newline
+
+      conds = nil
+
       unless @token.keyword?(:when)
-        cond = parse_op_assign_no_control
+        conds = [] of ASTNode
+
+        while true
+          conds << parse_op_assign_no_control
+          skip_space
+          if @token.type == :","
+            next_token_skip_space_or_newline
+          else
+            break
+          end
+        end
+
         skip_statement_end
       end
 
@@ -2110,15 +2124,19 @@ module Crystal
         when :IDENT
           case @token.value
           when :when
+            when_location = @token.location
+
             slash_is_regex!
             next_token_skip_space_or_newline
             when_conds = [] of ASTNode
             while true
-              if cond && @token.type == :"."
+              if conds && @token.type == :"."
                 next_token
                 call = parse_var_or_call(force_call: true) as Call
                 call.obj = ImplicitObj.new
                 when_conds << call
+              elsif conds && @token.type == :UNDERSCORE
+                when_conds << node_and_next_token(Underscore.new)
               else
                 when_conds << parse_op_assign_no_control
               end
@@ -2143,6 +2161,10 @@ module Crystal
               end
             end
 
+            if conds && conds.size > 1 && conds.size != when_conds.size
+              raise "wrong number of when expressions (given #{when_conds.size}, expected #{conds.size})", when_location
+            end
+
             slash_is_regex!
             when_body = parse_expressions
             skip_space_or_newline
@@ -2172,7 +2194,7 @@ module Crystal
         end
       end
 
-      Case.new(cond, whens, a_else)
+      Case.new(conds, whens, a_else)
     end
 
     def parse_include

src/compiler/crystal/syntax/to_s.cr

@@ -1145,9 +1145,12 @@ module Crystal
 
     def visit(node : Case)
       @str << keyword("case")
-      if cond = node.cond
+      if conds = node.conds
         @str << " "
-        cond.accept self
+        conds.each_with_index do |cond, i|
+          @str << ", " if i > 0
+          cond.accept self
+        end
       end
       newline
       node.whens.each do |wh|

src/compiler/crystal/syntax/transformer.cr

@@ -189,7 +189,7 @@ module Crystal
     end
 
     def transform(node : Case)
-      node.cond = node.cond.try &.transform(self)
+      transform_many node.conds
       transform_many node.whens
 
       if node_else = node.else

src/compiler/crystal/tools/formatter.cr

@@ -2648,9 +2648,18 @@ module Crystal
       write_keyword :case
       skip_space
 
-      if cond = node.cond
+      if conds = node.conds
         write " "
-        accept cond
+        conds.each_with_index do |cond, i|
+          accept cond
+          unless last?(i, conds)
+            skip_space
+            if @token.type == :","
+              write ", "
+              next_token_skip_space_or_newline
+            end
+          end
+        end
       end
 
       skip_space_write_line