From 49c322f120c421240e0d6409a715dcc4d683c9a2 Mon Sep 17 00:00:00 2001
From: Nick Treleaven <n@trelsoft.com>
Date: Tue, 8 Sep 2020 18:34:17 +0100
Subject: [PATCH] checker: simplify argument qualifier errors (#6321)

---
 vlib/v/ast/ast.v                 |  2 +-
 vlib/v/checker/checker.v         | 25 +++++--------------------
 vlib/v/checker/tests/mut_arg.out | 25 +++++++++++++++++++++++++
 vlib/v/checker/tests/mut_arg.vv  | 11 +++++++++++
 vlib/v/table/table.v             |  3 ++-
 5 files changed, 44 insertions(+), 22 deletions(-)
 create mode 100644 vlib/v/checker/tests/mut_arg.out
 create mode 100644 vlib/v/checker/tests/mut_arg.vv

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index ddc3340046..72ae6e5822 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -242,7 +242,7 @@ pub struct FnDecl {
 pub:
 	name          string
 	mod           string
-	args          []table.Arg
+	args          []table.Arg // parameters
 	is_deprecated bool
 	is_pub        bool
 	is_variadic   bool
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index a4435718b4..87d80c97b9 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1331,31 +1331,16 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 		if call_arg.is_mut {
 			c.fail_if_immutable(call_arg.expr)
 			if !arg.is_mut {
-				mut words := 'mutable'
-				mut tok := 'mut'
-				if call_arg.share == .shared_t {
-					words = 'shared'
-					tok = 'shared'
-				} else if call_arg.share == .atomic_t {
-					words = 'atomic'
-					tok = 'atomic'
-				}
-				c.error('`$arg.name` argument is not $words, `$tok` is not needed`', call_arg.expr.position())
+				tok := call_arg.share.str()
+				c.error('`$call_expr.name` parameter `$arg.name` is not `$tok`, `$tok` is not needed`',
+					call_arg.expr.position())
 			} else if arg.typ.share() != call_arg.share {
 				c.error('wrong shared type', call_arg.expr.position())
 			}
 		} else {
 			if arg.is_mut && (!call_arg.is_mut || arg.typ.share() != call_arg.share) {
-				mut words := ' mutable'
-				mut tok := 'mut'
-				if arg.typ.share() == .shared_t {
-					words = ' shared'
-					tok = 'shared'
-				} else if arg.typ.share() == .atomic_t {
-					words = 'n atomic'
-					tok = 'atomic'
-				}
-				c.error('`$arg.name` is a$words argument, you need to provide `$tok`: `${call_expr.name}($tok ...)`',
+				tok := call_arg.share.str()
+				c.error('`$call_expr.name` parameter `$arg.name` is `$tok`, you need to provide `$tok` e.g. `$tok arg${i+1}`',
 					call_arg.expr.position())
 			}
 		}
diff --git a/vlib/v/checker/tests/mut_arg.out b/vlib/v/checker/tests/mut_arg.out
new file mode 100644
index 0000000000..c3d2f1b3b3
--- /dev/null
+++ b/vlib/v/checker/tests/mut_arg.out
@@ -0,0 +1,25 @@
+vlib/v/checker/tests/mut_arg.vv:6:3: error: `f` parameter `par` is `mut`, you need to provide `mut` e.g. `mut arg1`
+    4 | }
+    5 |
+    6 | f([3,4])
+      |   ~~~~~
+    7 | mut a := [1,2]
+    8 | f(a)
+vlib/v/checker/tests/mut_arg.vv:8:3: error: `f` parameter `par` is `mut`, you need to provide `mut` e.g. `mut arg1`
+    6 | f([3,4])
+    7 | mut a := [1,2]
+    8 | f(a)
+      |   ^
+    9 |
+   10 | g(mut [3,4])
+vlib/v/checker/tests/mut_arg.vv:10:7: error: `g` parameter `par` is not `mut`, `mut` is not needed`
+    8 | f(a)
+    9 |
+   10 | g(mut [3,4])
+      |       ~~~~~
+   11 | g(mut a)
+vlib/v/checker/tests/mut_arg.vv:11:7: error: `g` parameter `par` is not `mut`, `mut` is not needed`
+    9 |
+   10 | g(mut [3,4])
+   11 | g(mut a)
+      |       ^
diff --git a/vlib/v/checker/tests/mut_arg.vv b/vlib/v/checker/tests/mut_arg.vv
new file mode 100644
index 0000000000..0a2afdd844
--- /dev/null
+++ b/vlib/v/checker/tests/mut_arg.vv
@@ -0,0 +1,11 @@
+fn f(mut par []int) {
+}
+fn g(par []int) {
+}
+
+f([3,4])
+mut a := [1,2]
+f(a)
+
+g(mut [3,4])
+g(mut a)
diff --git a/vlib/v/table/table.v b/vlib/v/table/table.v
index b2f5ac84e0..230bd4e3fa 100644
--- a/vlib/v/table/table.v
+++ b/vlib/v/table/table.v
@@ -22,7 +22,7 @@ pub mut:
 
 pub struct Fn {
 pub:
-	args                    []Arg
+	args                    []Arg // parameters
 	return_type             Type
 	return_type_source_name string
 	is_variadic             bool
@@ -39,6 +39,7 @@ pub mut:
 	name                    string
 }
 
+// parameter
 pub struct Arg {
 pub:
 	pos              token.Position