Small improvement of error message when doing yield inside a captur…

…ed proc. Related to #2711
crystal-lang · Jun 1, 2016 · a229d0b · a229d0b
1 parent 632f8e1
commit a229d0b
Showing 3 changed files with 18 additions and 7 deletions.
diff --git a/spec/compiler/type_inference/block_spec.cr b/spec/compiler/type_inference/block_spec.cr
@@ -940,7 +940,7 @@ describe "Block inference" do
     assert_error %(
       yield
       ),
-      "can't yield outside a method"
+      "can't use `yield` outside a method"
   end
 
   it "rebinds yield -> block arguments" do

diff --git a/spec/compiler/type_inference/closure_spec.cr b/spec/compiler/type_inference/closure_spec.cr
@@ -2,7 +2,11 @@ require "../../spec_helper"
 
 describe "Type inference: closure" do
   it "gives error when doing yield inside fun literal" do
-    assert_error "-> { yield }", "can't yield from function literal"
+    assert_error "-> { yield }", "can't use `yield` outside a method"
+  end
+
+  it "gives error when doing yield inside fun literal" do
+    assert_error "def foo; -> { yield }; end; foo {}", "can't use `yield` inside a proc literal or captured block"
   end
 
   it "marks variable as closured in program" do

diff --git a/src/compiler/crystal/semantic/main_visitor.cr b/src/compiler/crystal/semantic/main_visitor.cr
@@ -650,13 +650,20 @@ module Crystal
     end
 
     def visit(node : Yield)
-      if @fun_literal_context
-        node.raise "can't yield from function literal"
-      end
-
       call = @call
       unless call
-        node.raise "can't yield outside a method"
+        node.raise "can't use `yield` outside a method"
+      end
+
+      if ctx = @fun_literal_context
+        node.raise <<-MSG
+          can't use `yield` inside a proc literal or captured block
+
+          Make sure to read the whole docs section about blocks and procs,
+          including "Capturing blocks" and "Block forwarding":
+
+          http://crystal-lang.org/docs/syntax_and_semantics/blocks_and_procs.html
+          MSG
       end
 
       block = call.block || node.raise("no block given")