diff --git a/src/astbuilder.nit b/src/astbuilder.nit
index d0602eea2e..9c93bd0241 100644
--- a/src/astbuilder.nit
+++ b/src/astbuilder.nit
@@ -42,6 +42,12 @@ class ASTBuilder
 		return new AIntegerExpr.make(value, mmodule.int_type)
 	end
 
+	# Make a self expression
+	fun make_self: ASelfExpr
+	do
+		return new ASelfExpr
+	end
+
 	# Make a new instantiation
 	fun make_new(callsite: CallSite, args: nullable Array[AExpr]): ANewExpr
 	do
diff --git a/src/contracts.nit b/src/contracts.nit
index 132be36277..d4fc9c9e3b 100644
--- a/src/contracts.nit
+++ b/src/contracts.nit
@@ -70,7 +70,9 @@ redef class AModule
 	# Entry point to generate the entire contract infrastructure.
 	# Once this method is called we must call the `do_weaving_contracts` method (see it for more information).
 	fun do_contracts(toolcontext: ToolContext) do
-		var ast_builder = new ASTBuilder(mmodule.as(not null))
+		var mmodule = self.mmodule
+		if mmodule == null then return # Skip errir
+		var ast_builder = new ASTBuilder(mmodule)
 		#
 		var contract_visitor = new ContractsVisitor(toolcontext, toolcontext.modelbuilder.identified_modules.first, self, ast_builder)
 		contract_visitor.enter_visit(self)
diff --git a/src/examples/module_fictive.nit b/src/examples/module_fictive.nit
new file mode 100644
index 0000000000..39c8c45e83
--- /dev/null
+++ b/src/examples/module_fictive.nit
@@ -0,0 +1,61 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Sample program that show how to build (and run) a synthetic program from the AST builder
+import nitc::astprinter
+import nitc::interpreter
+import nitc::astbuilder
+
+# 3 god classes
+var tc = new ToolContext
+tc.keep_going = true
+var model = new Model
+var mb = new ModelBuilder(model, tc)
+
+# load the code module. While implicit in source code, we need to retrieve it for synthetic code
+var acore = mb.load_module("core")
+var mcore = acore.mmodule
+assert mcore != null
+# Loading does not perform the analysis, so force the analysis now
+mb.run_phases
+
+# A synthetic main module
+var mmodule = new MModule(model, null, "m0", model.no_location)
+mmodule.set_imported_mmodules([mcore]) # Close the module hierarchy
+mmodule.set_visibility_for(mcore, public_visibility) # Important, or else `_name` methods will fail
+
+# Refine Sys in the main module
+var mclass = mmodule.sys_type
+assert mclass != null
+var mclassdef = new MClassDef(mmodule, mclass, model.no_location)
+mclassdef.add_in_hierarchy # Close the classdef hierarchy
+
+# Redefine Sys::main
+var nmeth = mb.create_method_from_name("main", mclassdef, false)
+
+# Body is `self.print(42)`
+var ab = new ASTBuilder(mmodule, mclass)
+var narg = ab.make_int(42)
+var nrecv = ab.make_self
+var mprint = mb.try_get_mproperty_by_name2(null, mmodule, mclass, "print")
+assert mprint isa MMethod
+var callsite = ab.create_callsite(mprint, false)
+var ncall = ab.make_call(nrecv, callsite, [narg])
+nmeth.n_block.add(ncall)
+
+nmeth.dump_tree(false, false)
+ncall.print_tree
+
+var interpreter = new NaiveInterpreter(mb, mmodule, new Array[String])
+interpreter.start(mmodule)
diff --git a/src/examples/module_injected.nit b/src/examples/module_injected.nit
new file mode 100644
index 0000000000..2bb66cabf4
--- /dev/null
+++ b/src/examples/module_injected.nit
@@ -0,0 +1,42 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Sample program that show how to load (and run) a program from a String
+module module_injected
+
+import nitc::parser_util
+import nitc::astprinter
+import nitc::interpreter
+
+# 3 god classes
+var tc = new ToolContext
+tc.keep_going = true
+var model = new Model
+var mb = new ModelBuilder(model, tc)
+
+# Parse the module
+var amodule = tc.parse_module("print 42")
+# Add it to the model through the model builder
+var mmodule = mb.load_rt_module(null, amodule, "-")
+assert mmodule != null
+# Do the semantic analysis
+mb.run_phases
+
+amodule.dump_tree
+var main_method = amodule.n_classdefs.last.n_propdefs.first
+main_method.print_tree
+assert main_method isa AMethPropdef
+
+var interpreter = new NaiveInterpreter(mb, mmodule, new Array[String])
+interpreter.start(mmodule)
diff --git a/src/ffi/header_dependency.nit b/src/ffi/header_dependency.nit
index 84bbb298b4..dd596b24fe 100644
--- a/src/ffi/header_dependency.nit
+++ b/src/ffi/header_dependency.nit
@@ -68,6 +68,7 @@ private class HeaderDependancyPhase
 	redef fun process_nmodule(nmodule)
 	do
 		var mmodule = nmodule.mmodule
+		if mmodule == null then return # Skip error
 		mmodule.compute_header_dependencies(self)
 	end
 end
diff --git a/src/nit.nit b/src/nit.nit
index 6441b1a1f9..1f44fa2bfe 100644
--- a/src/nit.nit
+++ b/src/nit.nit
@@ -50,7 +50,6 @@ var mmodules: Array[MModule]
 
 if opt_eval.value then
 	var amodule = toolcontext.parse_module(progname)
-	toolcontext.check_errors
 
 	var parent = null
 	if opt_loop.value then
@@ -62,13 +61,14 @@ if opt_eval.value then
 	end
 
 	modelbuilder.load_rt_module(parent, amodule, "-")
+	toolcontext.check_errors
 
 	mmodules = [amodule.mmodule.as(not null)]
 else if progname == "-" then
 	var content = stdin.read_all
 	var amodule = toolcontext.parse_module(content)
-	toolcontext.check_errors
 	modelbuilder.load_rt_module(null, amodule, "-")
+	toolcontext.check_errors
 	mmodules = [amodule.mmodule.as(not null)]
 else
 	mmodules = modelbuilder.parse([progname])
diff --git a/src/parser/parser_nodes.nit b/src/parser/parser_nodes.nit
index f19547d159..120ea68cdf 100644
--- a/src/parser/parser_nodes.nit
+++ b/src/parser/parser_nodes.nit
@@ -26,6 +26,11 @@ abstract class ANode
 	# However, manual instantiated nodes may need more care.
 	var location: Location is writable, noinit
 
+	fun has_location: Bool
+	do
+		return isset self._location
+	end
+
 	# The location of the important part of the node (identifier or whatever)
 	fun hot_location: Location do return location
 
@@ -235,7 +240,11 @@ class ASTDump
 
 	redef fun display(n)
 	do
-		return "{n.class_name} {n.dump_info(self)} @{n.location}"
+		if n.has_location then
+			return "{n.class_name} {n.dump_info(self)} @{n.location}"
+		else
+			return "{n.class_name} {n.dump_info(self)}"
+		end
 	end
 
 	# `s` as yellow
@@ -382,7 +391,13 @@ abstract class Token
 
 	redef fun is_structural do return true
 
-	redef fun dump_info(v) do return " {text.escape_to_c}"
+	redef fun dump_info(v) do
+		if has_location then
+			return " {text.escape_to_c}"
+		else
+			return ""
+		end
+	end
 
 	# Loose tokens that precede `self`.
 	#
diff --git a/src/toolcontext.nit b/src/toolcontext.nit
index 0797723308..19045e95d9 100644
--- a/src/toolcontext.nit
+++ b/src/toolcontext.nit
@@ -416,6 +416,8 @@ class ToolContext
 		opt_stub_man.hidden = true
 		opt_bash_completion.hidden = true
 		opt_set_dummy_tool.hidden = true
+
+		nit_dir = locate_nit_dir
 	end
 
 	# Name, usage and synopsis of the tool.
@@ -503,6 +505,10 @@ The Nit language documentation and the source code of its tools and libraries ma
 		end
 
 		nit_dir = locate_nit_dir
+		if nit_dir == null then
+			fatal_error(null, "Fatal Error: cannot locate a valid base Nit directory. It is quite unexpected. Try to set the environment variable `NIT_DIR` or to use the `--nit-dir` option.")
+			abort
+		end
 
 		if option_context.rest.is_empty and not accept_no_arguments then
 			print tooldescription
@@ -577,7 +583,7 @@ The Nit language documentation and the source code of its tools and libraries ma
 	#
 	# The result is returned without being assigned to `nit_dir`.
 	# This function is automatically called by `process_options`
-	fun locate_nit_dir: String
+	fun locate_nit_dir: nullable String
 	do
 		# the option has precedence
 		var res = opt_nit_dir.value
@@ -617,8 +623,7 @@ The Nit language documentation and the source code of its tools and libraries ma
 			if check_nit_dir(res) then return res.simplify_path
 		end
 
-		fatal_error(null, "Fatal Error: cannot locate a valid base Nit directory. It is quite unexpected. Try to set the environment variable `NIT_DIR` or to use the `--nit-dir` option.")
-		abort
+		return null
 	end
 
 	private fun check_nit_dir(res: String): Bool
diff --git a/tests/nitcg.skip b/tests/nitcg.skip
index 3c378aa029..e61d597669 100644
--- a/tests/nitcg.skip
+++ b/tests/nitcg.skip
@@ -11,3 +11,5 @@ get_mclasses
 ^nit
 test_astbuilder
 test_astprinter
+module_fictive
+module_injected
diff --git a/tests/niti.skip b/tests/niti.skip
index 551351b0d6..340b280e0b 100644
--- a/tests/niti.skip
+++ b/tests/niti.skip
@@ -48,3 +48,5 @@ nitpm
 nitdoc
 test_astbuilder
 test_astprinter
+module_fictive
+module_injected
diff --git a/tests/sav/module_fictive.res b/tests/sav/module_fictive.res
new file mode 100644
index 0000000000..8edc936ff3
--- /dev/null
+++ b/tests/sav/module_fictive.res
@@ -0,0 +1,11 @@
+AMethPropdef  @
+|--APublicVisibility 
+|--AIdMethid 
+|--ASignature 
+`--ABlockExpr 
+   `--ACallExpr  call=Sys.file$Sys$print(object: Object)
+      |--ASelfExpr 
+      `--AListExprs 
+         `--AIntegerExpr :Int
+self.print(42)
+42
diff --git a/tests/sav/module_injected.res b/tests/sav/module_injected.res
new file mode 100644
index 0000000000..bc55b36d31
--- /dev/null
+++ b/tests/sav/module_injected.res
@@ -0,0 +1,14 @@
+1	print 42
+AModule  @1,1--8
+`--AMainClassdef  @1,1--8
+   `--AMainMethPropdef  @1,1--8
+      `--ABlockExpr  @1,1--8
+         `--ACallExpr  call=Sys.file$Sys$print(object: Object) @1,1--8
+            |--AImplicitSelfExpr :Sys @1,1
+            |--AQid  @1,1--5
+            |  `--TId  print @1,1--5
+            `--AListExprs  @1,7--8
+               `--AIntegerExpr :Int @1,7--8
+                  `--TInteger  42 @1,7--8
+print(42)
+42