mathlib commit https://github.com/leanprover-community/mathlib/commit/65a1391a0106c9204fe45bc73a039f056558cb83

@@ -71,7 +71,7 @@ theorem heron {p1 p2 p3 : P} (h1 : p1 ≠ p2) (h2 : p3 ≠ p2) :
       ring
     _ = 1 / 4 * √ (s * (s - a) * (s - b) * (s - c) * 4 ^ 2) := by simp only [s]; ring_nf
     _ = √ (s * (s - a) * (s - b) * (s - c)) := by
-      rw [sqrt_mul', sqrt_sq, div_mul_eq_mul_div, one_mul, mul_div_cancel] <;> norm_num
+      rw [sqrt_mul', sqrt_sq, div_mul_eq_mul_div, one_mul, mul_div_cancel_right₀] <;> norm_num
 #align theorems_100.heron Theorems100.heron
 
 end Theorems100

mathlib commit https://github.com/leanprover-community/mathlib/commit/ce64cd319bb6b3e82f31c2d38e79080d377be451

@@ -3,7 +3,7 @@ Copyright (c) 2021 Matt Kempster. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Matt Kempster
 -/
-import Mathbin.Geometry.Euclidean.Triangle
+import Geometry.Euclidean.Triangle
 
 #align_import wiedijk_100_theorems.herons_formula from "leanprover-community/mathlib"@"08b081ea92d80e3a41f899eea36ef6d56e0f1db0"
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/8ea5598db6caeddde6cb734aa179cc2408dbd345

@@ -2,14 +2,11 @@
 Copyright (c) 2021 Matt Kempster. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Matt Kempster
-
-! This file was ported from Lean 3 source module wiedijk_100_theorems.herons_formula
-! leanprover-community/mathlib commit 08b081ea92d80e3a41f899eea36ef6d56e0f1db0
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathbin.Geometry.Euclidean.Triangle
 
+#align_import wiedijk_100_theorems.herons_formula from "leanprover-community/mathlib"@"08b081ea92d80e3a41f899eea36ef6d56e0f1db0"
+
 /-!
 # Freek № 57: Heron's Formula
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/bf2428c9486c407ca38b5b3fb10b87dad0bc99fa

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Matt Kempster
 
 ! This file was ported from Lean 3 source module wiedijk_100_theorems.herons_formula
-! leanprover-community/mathlib commit 5563b1b49e86e135e8c7b556da5ad2f5ff881cad
+! leanprover-community/mathlib commit 08b081ea92d80e3a41f899eea36ef6d56e0f1db0
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -13,6 +13,9 @@ import Mathbin.Geometry.Euclidean.Triangle
 /-!
 # Freek № 57: Heron's Formula
 
+> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
+> Any changes to this file require a corresponding PR to mathlib4.
+
 This file proves Theorem 57 from the [100 Theorems List](https://www.cs.ru.nl/~freek/100/),
 also known as Heron's formula, which gives the area of a triangle based only on its three sides'
 lengths.

mathlib commit https://github.com/leanprover-community/mathlib/commit/893964fc28cefbcffc7cb784ed00a2895b4e65cf

@@ -3,8 +3,8 @@ Copyright (c) 2021 Matt Kempster. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Matt Kempster
 
-! This file was ported from Lean 3 source module «100-theorems-list».«57_herons_formula»
-! leanprover-community/mathlib commit 328375597f2c0dd00522d9c2e5a33b6a6128feeb
+! This file was ported from Lean 3 source module wiedijk_100_theorems.herons_formula
+! leanprover-community/mathlib commit 5563b1b49e86e135e8c7b556da5ad2f5ff881cad
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/

List.mem_split duplicates List.append_of_mem from Std: https://github.com/leanprover/std4/blob/a756b7d643ae5dcd7bf314e99f8e493e5d81b9ed/Std/Data/List/Lemmas.lean#L94-L96

This PR makes it an alias.

Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>

@@ -67,7 +67,7 @@ theorem heron {p1 p2 p3 : P} (h1 : p1 ≠ p2) (h2 : p3 ≠ p2) :
       field_simp [numerator, denominator, ab2_nonneg]; ring
     _ = ↑1 / ↑4 * √ (s * (s - a) * (s - b) * (s - c) * ↑4 ^ 2) := by simp only [s]; ring_nf
     _ = √ (s * (s - a) * (s - b) * (s - c)) := by
-      rw [sqrt_mul', sqrt_sq, div_mul_eq_mul_div, one_mul, mul_div_cancel] <;> norm_num
+      rw [sqrt_mul', sqrt_sq, div_mul_eq_mul_div, one_mul, mul_div_cancel_right₀] <;> norm_num
 #align theorems_100.heron Theorems100.heron
 
 end Theorems100

Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

@@ -57,15 +57,15 @@ theorem heron {p1 p2 p3 : P} (h1 : p1 ≠ p2) (h2 : p3 ≠ p2) :
       (sub_nonneg.mpr (cos_sq_le_one γ)).trans_eq split_to_frac
     cases' div_nonneg_iff.mp frac_nonneg with h h
     · exact h.left
-    · simpa [h1, h2] using le_antisymm h.right (sq_nonneg _)
+    · simpa [numerator, denominator, a, b, c, h1, h2] using le_antisymm h.right (sq_nonneg _)
   have ab2_nonneg : 0 ≤ 2 * a * b := by positivity
   calc
     1 / 2 * a * b * sin γ = 1 / 2 * a * b * (√ numerator / √ denominator) := by
       rw [sin_eq_sqrt_one_sub_cos_sq, split_to_frac, sqrt_div numerator_nonneg] <;>
-        simp [angle_nonneg, angle_le_pi]
+        simp [γ, angle_nonneg, angle_le_pi]
     _ = 1 / 4 * √ ((2 * a * b) ^ 2 - (a * a + b * b - c * c) ^ 2) := by
-      field_simp [ab2_nonneg]; ring
-    _ = ↑1 / ↑4 * √ (s * (s - a) * (s - b) * (s - c) * ↑4 ^ 2) := by simp only; ring_nf
+      field_simp [numerator, denominator, ab2_nonneg]; ring
+    _ = ↑1 / ↑4 * √ (s * (s - a) * (s - b) * (s - c) * ↑4 ^ 2) := by simp only [s]; ring_nf
     _ = √ (s * (s - a) * (s - b) * (s - c)) := by
       rw [sqrt_mul', sqrt_sq, div_mul_eq_mul_div, one_mul, mul_div_cancel] <;> norm_num
 #align theorems_100.heron Theorems100.heron

@@ -58,7 +58,7 @@ theorem heron {p1 p2 p3 : P} (h1 : p1 ≠ p2) (h2 : p3 ≠ p2) :
     cases' div_nonneg_iff.mp frac_nonneg with h h
     · exact h.left
     · simpa [h1, h2] using le_antisymm h.right (sq_nonneg _)
-  have ab2_nonneg : 0 ≤ 2 * a * b := by simp [mul_nonneg, dist_nonneg]
+  have ab2_nonneg : 0 ≤ 2 * a * b := by positivity
   calc
     1 / 2 * a * b * sin γ = 1 / 2 * a * b * (√ numerator / √ denominator) := by
       rw [sin_eq_sqrt_one_sub_cos_sq, split_to_frac, sqrt_div numerator_nonneg] <;>

PR contents

This is the supremum of

• #8284
• #8056
• #8023
• #8332
• #8226 (already approved)
• #7834 (already approved)

along with some minor fixes from failures on nightly-testing as Mathlib master is merged into it.

Note that some PRs for changes that are already compatible with the current toolchain and will be necessary have already been split out: #8380.

I am hopeful that in future we will be able to progressively merge adaptation PRs into a bump/v4.X.0 branch, so we never end up with a "big merge" like this. However one of these adaptation PRs (#8056) predates my new scheme for combined CI, and it wasn't possible to keep that PR viable in the meantime.

Lean PRs involved in this bump

In particular this includes adjustments for the Lean PRs

• leanprover/lean4#2778
• leanprover/lean4#2790
• leanprover/lean4#2783
• leanprover/lean4#2825
• leanprover/lean4#2722

leanprover/lean4#2778

We can get rid of all the

local macro_rules | `($x ^ $y) => `(HPow.hPow $x $y) -- Porting note: See issue [lean4#2220](https://github.com/leanprover/lean4/pull/2220)

macros across Mathlib (and in any projects that want to write natural number powers of reals).

leanprover/lean4#2722

Changes the default behaviour of simp to (config := {decide := false}). This makes simp (and consequentially norm_num) less powerful, but also more consistent, and less likely to blow up in long failures. This requires a variety of changes: changing some previously by simp or norm_num to decide or rfl, or adding (config := {decide := true}).

leanprover/lean4#2783

This changed the behaviour of simp so that simp [f] will only unfold "fully applied" occurrences of f. The old behaviour can be recovered with simp (config := { unfoldPartialApp := true }). We may in future add a syntax for this, e.g. simp [!f]; please provide feedback! In the meantime, we have made the following changes:

• switching to using explicit lemmas that have the intended level of application
• (config := { unfoldPartialApp := true }) in some places, to recover the old behaviour
• Using @[eqns] to manually adjust the equation lemmas for a particular definition, recovering the old behaviour just for that definition. See #8371, where we do this for Function.comp and Function.flip.

This change in Lean may require further changes down the line (e.g. adding the !f syntax, and/or upstreaming the special treatment for Function.comp and Function.flip, and/or removing this special treatment). Please keep an open and skeptical mind about these changes!

Co-authored-by: leanprover-community-mathlib4-bot <leanprover-community-mathlib4-bot@users.noreply.github.com> Co-authored-by: Scott Morrison <scott.morrison@gmail.com> Co-authored-by: Eric Wieser <wieser.eric@gmail.com> Co-authored-by: Mauricio Collares <mauricio@collares.org>

@@ -25,8 +25,6 @@ open Real EuclideanGeometry
 
 open scoped Real EuclideanGeometry
 
-local macro_rules | `($x ^ $y) => `(HPow.hPow $x $y) -- Porting note: See issue lean4#2220
-
 namespace Theorems100
 
 local notation "√" => Real.sqrt

cliqueFree_of_replaceVertex_cliqueFree is still quite long.

@@ -31,7 +31,7 @@ namespace Theorems100
 
 local notation "√" => Real.sqrt
 
-variable {V : Type _} {P : Type _} [NormedAddCommGroup V] [InnerProductSpace ℝ V] [MetricSpace P]
+variable {V : Type*} {P : Type*} [NormedAddCommGroup V] [InnerProductSpace ℝ V] [MetricSpace P]
   [NormedAddTorsor V P]
 
 /-- **Heron's formula**: The area of a triangle with side lengths `a`, `b`, and `c` is

@@ -25,7 +25,7 @@ open Real EuclideanGeometry
 
 open scoped Real EuclideanGeometry
 
-local macro_rules | `($x ^ $y) => `(HPow.hPow $x $y) -- Porting note: See issue #2220
+local macro_rules | `($x ^ $y) => `(HPow.hPow $x $y) -- Porting note: See issue lean4#2220
 
 namespace Theorems100
 

• depends on: #5966

Co-authored-by: Eric Wieser <wieser.eric@gmail.com> Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

@@ -2,14 +2,11 @@
 Copyright (c) 2021 Matt Kempster. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Matt Kempster
-
-! This file was ported from Lean 3 source module wiedijk_100_theorems.herons_formula
-! leanprover-community/mathlib commit 5563b1b49e86e135e8c7b556da5ad2f5ff881cad
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathlib.Geometry.Euclidean.Triangle
 
+#align_import wiedijk_100_theorems.herons_formula from "leanprover-community/mathlib"@"5563b1b49e86e135e8c7b556da5ad2f5ff881cad"
+
 /-!
 # Freek № 57: Heron's Formula