[Bug #21784] Fix the Proc#source_location start_column for stabby lambdas

* Consistent with plain `blocks` and `for` blocks and methods
  where the source_location covers their entire definition.
* Matches the documentation which mentions
  "where the definition starts/ends".
* Partially reverts d357d50
  which was a workaround to be compatible with parse.y.

Author: eregon

parse.y

@@ -5149,7 +5149,7 @@ lambda		: tLAMBDA[lpar]
                         CMDARG_POP();
                         $args = args_with_numbered(p, $args, max_numparam, it_id);
                         {
-                            YYLTYPE loc = code_loc_gen(&@args, &@body);
+                            YYLTYPE loc = code_loc_gen(&@lpar, &@body);
                             $$ = NEW_LAMBDA($args, $body->node, &loc, &@lpar, &$body->opening_loc, &$body->closing_loc);
                             nd_set_line(RNODE_LAMBDA($$)->nd_body, @body.end_pos.lineno);
                             nd_set_line($$, @args.end_pos.lineno);

prism_compile.c

@@ -3284,13 +3284,6 @@ pm_scope_node_init(const pm_node_t *node, pm_scope_node_t *scope, pm_scope_node_
         scope->parameters = cast->parameters;
         scope->body = cast->body;
         scope->locals = cast->locals;
-
-        if (cast->parameters != NULL) {
-            scope->base.location.start = cast->parameters->location.start;
-        }
-        else {
-            scope->base.location.start = cast->operator_loc.end;
-        }
         break;
       }
       case PM_MODULE_NODE: {

spec/ruby/core/proc/source_location_spec.rb

@@ -61,7 +61,7 @@
     ruby_version_is("4.0") do
       proc { true }.source_location.should == [__FILE__, __LINE__, 11, __LINE__, 19]
       Proc.new { true }.source_location.should == [__FILE__, __LINE__, 15, __LINE__, 23]
-      -> { true }.source_location.should == [__FILE__, __LINE__, 8, __LINE__, 17]
+      -> { true }.source_location.should == [__FILE__, __LINE__, 6, __LINE__, 17]
     end
   end
 
@@ -98,7 +98,7 @@
       location.should == ["foo", 100]
     end
     ruby_version_is("4.0") do
-      location.should == ["foo", 100, 2, 100, 5]
+      location.should == ["foo", 100, 0, 100, 5]
     end
   end
 end

test/ruby/test_ast.rb

@@ -1230,7 +1230,7 @@ def test_error_tolerant_end_is_short_for_do_LAMBDA
        args: nil
        body:
          (LAMBDA@1:0-2:3
-            (SCOPE@1:2-2:3
+            (SCOPE@1:0-2:3
              tbl: []
              args:
                (ARGS@1:2-1:2

test/ruby/test_lambda.rb

@@ -276,7 +276,7 @@ def test_break
   end
 
   def test_do_lambda_source_location
-    exp = [__LINE__ + 1, 12, __LINE__ + 5, 7]
+    exp = [__LINE__ + 1, 10, __LINE__ + 5, 7]
     lmd = ->(x,
              y,
              z) do
@@ -288,7 +288,7 @@ def test_do_lambda_source_location
   end
 
   def test_brace_lambda_source_location
-    exp = [__LINE__ + 1, 12, __LINE__ + 5, 5]
+    exp = [__LINE__ + 1, 10, __LINE__ + 5, 5]
     lmd = ->(x,
              y,
              z) {